unionfs

package: unionfs

title: unionfs(8)

summary: A userspace unionfs implementation

text:
# unionfs(8)

## NAME
unionfs-fuse - A userspace unionfs implementation

## SYNOPSIS
unionfs [-o option1 -o option2 ... -o optionN ]

top_branch:lower_branch:...:lowest_branch

mount_point

## DESCRIPTION
unionfs overlays several directory into one single mount point.

It first tries to access the file on the top branch and if the file does not exist there, it continues on lower level branches. If the user tries to modify a file on a lower level read-only branch the file is copied to a higher level read-write branch if the copy-on-write (cow) mode was enabled.

## OPTIONS
Below is a summary of unionfs options

-o chroot=path

Path to chroot into. By using this option unionfs may be used for live CDs or live USB sticks, etc. So it can serve "/" as filesystem. If you do not specify this option and try to use it for "/" it will deadlock on calling 'pivot_root'. If you do set this option, you also need to specify the branches relativly to the given chroot directory. See examples/S01a-unionfs-live-cd.sh for an example.

-o cow

Enable copy-on-write

-o hide_meta_files

In our unionfs root path we have a .unionfs directory that includes metadata, such as hidden (deleted) files. This options make this directory invisible from readdir(), so for example "ls -la /union_root/" will not show it. However, this directory is still there and "cd .unionfs" or "ls -l .unionfs" still work. Also, libfuse will create .fuse_hidden* files, if a file is open, but will be deleted. Those fuse meta files also will be invisble. This option is especially usufull for package builders.

-d

Enable debugging for unionfs and libfuse. Useful for developers if the code if the code does not behave as expected. Debug information will be written to stderr and a debug file (./unionfs_debug.log by default).

-o debug_file=file

Write unionfs debug information into that file.

-o max_files=number

Maximum number of open files. Most system have a default of 1024 open files per process. For example if unionfs serves "/" applications like KDE or GNOME might have much more open files, which will make the unionfs process to exceed this limit. Suggested for "/" is >16000 or even >32000 files. If this limit exceeds unionfs will not be able to open further files.

-o noinitgroups

Since version 0.23 without any effect, just left over for compatibility. Might be removed in future versions.

-o relaxed_permissions

Usually we automatically add the libfuse option "-odefault_permissions" so that libfuse takes over permission checks. However, if running not as root (so as uid =! 0 and gid != 0), permissions of the underlying filesystem are already sufficient. In order to prevent from severe security issues, this option is not allowed if running as root.

-o statfs_omit_ro

By default blocks of all branches are counted in statfs() calls (e.g. by 'df'). On setting this option read-only branches will be omitted for the summary of blocks. This may sound weird but it actually fixes "wrong" percentage of free space.

## Options to libfuse
There are several further options available, which don't directly apply to unionfs, but to libfuse. Please run "unionfs --help" to see these. We already set the "-o default-permissions" options on our own.

## EXAMPLES

```
 unionfs -o cow,max_files=32768 \
              -o allow_other,use_ino,suid,dev,nonempty \
              /u/host/etc=RW:/u/group/etc=RO:/u/common/etc=RO \
              /u/union/etc
```

## Meta data
Like other filesystems unionfs also needs to store meta data. Well, presently only information about deleted files and directories need to be stored, but in future releases more information might be required, e.g. inode-numbers for persistent inode information. Meta data information are saved and looked for in the .unionfs/ directories of each branch-root. So in the example above, these are /u/host/etc/.unionfs, /u/group/etc/.unionfs and /u/common/etc/.unionfs. Within these directories a complete directory structure may be found. Example: If the admin decides to delete the file /etc/test/testfile, which only exists in /u/unionfs/etc/test/testfile, unionfs can't delete this file, since it is on a read-only branch. So instead the whiteout file /u/host/etc/.unionfs/test/testfile_HIDDEN~ will be created. So on accessing the union filesystem, test/testfile will not be visible. Please also note that whiteout files/directories will only hide the files in lower level branches. So for example whiteouts in the group directory (/u/group/etc/.unionfs of the example above) will only hide file of the common branch (/u/common/etc), but not these of the group and host branches. Especially for diskless-booted environments it is rather useful for the admin to create whiteout files him/her-self. For example one should blacklist network re-initializations, /etc/mtab, /etc/nologin of the server and several cron-scripts. This can be easily achieved by creating whiteout files for these scripts in the group meta directory.

## KNOWN ISSUES

```
1) Another issue is that presently there is no support for read-only branches
when copy-on-write is disabled, thus, -ocow is NOT specified! Support for
that might be added in later releases.
```

## AUTHORS
unionfs-fuse Original implemention by Radek Podgorny <radek@podgorny.cz>

## COPYRIGHT
Radek Podgorny <radek@podgorny.cz>, Bernd Schubert <bernd-schubert@gmx.de>

## THANKS
Many thanks to the author of the FUSE filesystem Miklos Szeredi.


unitd

package: unit

title: unitd(8)

summary: runs the NGINX Unit daemon

text:
# unitd(8)

## Name
unitd — runs the NGINX Unit daemon

## Synopsis
unitd [--no-daemon] [--control socket] [--control-mode mode] [--control-user user] [--control-group group] [--group name] [--user name] [--log file] [--modulesdir directory] [--pid file] [--statedir directory] unitd [-h | --help | --version]

## Description
NGINX Unit is a polyglot app server, a reverse proxy, and a static file server for UNIX-like systems. It was built by nginx(8) team members from scratch to be highly efficient and fully configurable at runtime.

## Options
-h, --help

Displays a summary of Unit's command-line options and their compile-time defaults.

--version

Displays Unit's version and the ./configure settings it was built with.

--no-daemon

Runs Unit in non-daemon mode.

--control socket

Overrides the control API's socket address in IPv4, IPv6, or UNIX-domain format.

--control-mode mode

Sets the permission of the UNIX-domain control socket.

--control-user user

Sets the owner of the UNIX-domain control socket.

--control-group group

Sets the group of the UNIX-domain control socket.

--group name, --user name

Override group name and user name used to run Unit's non-privileged processes.

--log file

Overrides the pathname for Unit's log.

--modulesdir directory

Overrides the directory path for Unit's language modules (*.unit.so) files.

--pid file

Overrides the pathname for the PID file of Unit's main process.

--statedir directory

Overrides the directory path for Unit's state storage.

## Exit status
Exit status is 0 on success, or 1 if the daemon encounters an error.

## Files
/run/unit/unit.pid

The PID file of Unit's main process.

/var/log/unit/unit.log

A general-purpose log for diagnostics and troubleshooting.

## Sockets
unix:/run/unit/control.sock

The socket address of Unit's control API.

## Copyright

```
(C) 2017-2025 NGINX, Inc.
(C) 2017-2025 Andrei Zeliankou
(C) 2018-2025 Konstantin Pavlov
(C) 2021-2025 Zhidao Hong
(C) 2022-2025 Andrew Clayton
(C) 2022-2025 Liam Crilly
(C) 2023-2025 Dan Callahan
(C) 2023-2025 Igor Ippolitov
(C) 2024-2025 Ava Hahn
(C) 2023-2024 Danielle De Leo
(C) 2023-2024 Dylan Arbour
(C) 2023-2024 Gabor Javorszky
(C) 2023-2024 Taryn Musgrave
(C) 2021-2023 Alejandro Colomar
(C) 2017-2022 Valentin V. Bartenev
(C) 2017-2022 Max Romanov
(C) 2021-2022 Oisín Canty
(C) 2017-2021 Igor Sysoev
(C) 2017-2021 Andrei Belov
(C) 2019-2021 Tiago Natel de Moura
(C) 2019-2020 Axel Duch
(C) 2018-2019 Alexander Borisov
```

SPDX-License-Identifier: Apache-2.0

## See also
Website

User mailing list

GitHub


update-kernel

package: update-kernel

title: update-kernel(8)

summary: Linux kernel update tool

text:
# update-kernel(8)

## NAME
update-kernel - Linux kernel update tool

## SYNOPSIS
update-kernel [options]

## DESCRIPTION
update-kernel - script to conveniently update kernel and modules.

It works by installing a new package set along with existing kernel, old kernel is kept so that you don´t end up without a kernel guaranteed to boot (your good old one); by default, it will look for the most recent package of the same flavour (e.g. "std-def") and try to install all the same modules as already installed for that.

## OPTIONS
-l, --list

list available kernels

-a, --all

install all kernel modules

-i, --interactive

interactive modules install

-H, --headers

add kernel headers to install

-A modulename

include (add) external module (by a short name)

-D modulename

exclude (del) external module from install

-f, -y, --force

force kernel upgrade (without confirmation dialog)

-t, --type

install kernel with specified flavour (un-def, std-def, etc)

-r, --release

desired kernel release (allowed formats by example:

old format: alt1, 5.7.19-alt1

classic kernel release: 5.7.19-std-def-alt1

package name: [kernel-image-]std-def-5.7.19-alt1)

-n, --dry-run

perform a simulation of events that would occur but do not actually change the system

-d, --download-only

download packages but don't install

-h, --help

show this text and exit

Run remove-old-kernels to uninstall unused kernels.

## EXAMPLES
Download and install latest un-def kernel:

update-kernel -t un-def

Download and install specific kernel version (Note: it should exist in

repository): update-kernel -r 5.15.70-un-def-alt1

## EXIT STATUS
update-kernel returns a zero exit status if it succeeds. Non zero is returned in case of failure.

## AUTHOR
Man page by Anton Shevtsov (shevtsov.anton (at) gmail.com)

## SEE ALSO
apt-get(8)


upowerd

package: upower

title: upowerd(8)

summary: UPower Daemon

text:
# upowerd(8)

## NAME
upowerd - UPower Daemon

## SYNOPSIS
upowerd [--help]

## DESCRIPTION
upowerd provides the org.freedesktop.UPower service on the system message bus. Users or administrators should never need to start this daemon as it will be automatically started by dbus-daemon(1) whenever an application calls into the org.freedesktop.UPower service.

## OPTIONS
--help

Show help options.

## AUTHOR
Written by David Zeuthen <davidz@redhat.com> with a lot of help from many others.

## BUGS
Please send bug reports to either the distribution or the DeviceKit mailing list, see http://lists.freedesktop.org/mailman/listinfo/devkit-devel on how to subscribe.

## SEE ALSO
UPower(7), upower(1), dbus-daemon(1),


usbip

package: usbip

title: usbip(8)

summary: manage USB/IP devices

text:
# usbip(8)

## NAME
usbip - manage USB/IP devices

## SYNOPSIS
usbip [options] <command> <args>

## DESCRIPTION
On a USB/IP server, devices can be listed, bound, and unbound using this program. On a USB/IP client, devices exported by USB/IP servers can be listed, attached and detached.

## OPTIONS
--debug

Print debugging information.

--log

Log to syslog.

--tcp-port PORT

Connect to PORT on remote host (used for attach and list --remote).

## COMMANDS
version

Show version and exit.

help [command]

Print the program help message, or help on a specific command, and then exit.

attach --remote=<host> --busid=<bus_id>

Attach a remote USB device.

detach --port=<port>

Detach an imported USB device.

bind --busid=<busid>

Make a device exportable.

unbind --busid=<busid>

Stop exporting a device so it can be used by a local driver.

list --remote=<host>

List USB devices exported by a remote host.

list --local

List local USB devices.

## EXAMPLES

client:# usbip list --remote=server

- List devices exported by remote server.

client:# modprobe vhci-hcd

client:# usbip attach --remote=server --busid=1-2

- Connect the remote USB device.

client:# usbip detach --port=0

- Detach the usb device.

## SEE ALSO
usbipd(8)


usbipd

package: usbip-server

title: usbipd(8)

summary: USB/IP server daemon

text:
# usbipd(8)

## NAME
usbipd - USB/IP server daemon

## SYNOPSIS
usbipd [options]

## DESCRIPTION
usbipd provides USB/IP clients access to exported USB devices.

Devices have to explicitly be exported using usbip bind before usbipd makes them available to other hosts.

The daemon accepts connections from USB/IP clients on TCP port 3240 by default.

## OPTIONS
-4, --ipv4

Bind to IPv4. Default is both.

-6, --ipv6

Bind to IPv6. Default is both.

-D, --daemon

Run as a daemon process.

-d, --debug

Print debugging information.

-PFILE, --pid FILE

Write process id to FILE.

If no FILE specified, use /var/run/usbipd.pid

-tPORT, --tcp-port PORT

Listen on TCP/IP port PORT.

-h, --help

Print the program help message and exit.

-v, --version

Show version.

## LIMITATIONS
usbipd offers no authentication or authorization for USB/IP. Any USB/IP client can connect and use exported devices.

## EXAMPLES

server:# modprobe usbip-host

server:# usbipd -D

- Start usbip daemon.

server:# usbip list --local

- List driver assignments for usb devices.

server:# usbip bind --busid=1-2

- Bind usbip-host.ko to the device of busid 1-2.

- A usb device 1-2 is now exportable to other hosts!

- Use 'usbip unbind --busid=1-2' when you want to shutdown exporting and use the device locally.

## SEE ALSO
usbip(8)


usbmon

package: usbmon

title: usbmon(8)

summary: monitor USB traffic

text:
# usbmon(8)

## NAME
usbmon - monitor USB traffic

## SYNOPSIS
usbmon [ -i bus_num ] [ -s length ] [ -f0 | -fu | -fh ] [ -a0 | -a1 ]

## DESCRIPTION
usbmon allows to capture USB traffic for analysis in the manner similar to tcpdump (8).

To make use of this program, you need to have a Linux kernel which supports the binary "usbmon" interface (e.g., Linux kernel 2.6.20 or newer).

## OPTIONS
-i

Listen on bus_num. If unspecified, usbmon attempts to listen on the pseudo-bus number zero, which is supposed to capture all packets on all buses. The default is a convenient mode because the user does not have to figure out the bus number where a specific device is attached. Also, listening on pseudo-bus zero allows to capture events which happen when a bus is initialized. However, it may be necessary to specify a specific bus number to tap. Kernels before 2.6.22 do not implement the pseudo-bus zero at all. Performance of USB stack and the usbmon is greater when a specific bus is monitored. In such case, the desired bus number may be determined by examining the output of lsusb(8).

-s

Set the maximum length of USB data to print. The default is to print 32 bytes just like the kernel's text interface would. The capture size is automatically adjusted to match unless set explicitly.

-f

Select the output format as one of: '0' for legacy format, 'u' for so-called "1u" format, 'h' for "human-readable" format. The human-readable format is the default. Also, it changes over time, so programs should parse the "1u" format. Selecting the 1u format forces usbmon to use the API which may not be available in the kernel before version 2.6.22.

The human-readable format is not intended for a programmatic parsing, and so changes from release to release.

-a

Force the binary API version to use: '0' for the legacy API in kernel 2.6.20 and up, '1' for the newer API in kernels after 2.6.22. Selection of output format may force the API to the minimum required to support the format. In general, this option is only used when testing the kernel component of usbmon.

## OUTPUT FORMAT
The output of usbmon contains one text line per an event. The event corresponds to I/O operations on the boundary of Host Controller Driver (HCD). This includes events of the following types: Submission, Callback, Error. Every line consists of whitespace separated words. The number or position of words may depend on the event type, but there is a set of words, common for all types.

Most commonly used format is the human-readable format. Its words, from left to right, are:

- URB Tag. A single URB generates several monitoring events during its life cycle. The tag allows to corellate events with the URB. Tag is usually derived from a kernel mode address. Human-readable format shortens the tag to make the output more readable, so it's not the complete address.

- Timestamp. It consistes of the number of seconds, period, and the fraction in microseconds.

- Event Type. This type refers to the format of the event, not URB type. Available types are: S - submission, C - callback, E - submission error.

- "Pipe word" (the name is historical and has nothing to do with pipes). This is a composite word. It consists of four fields, separated by colons: URB type and direction, Bus number, Device address, Endpoint number. Type and direction are encoded with two bytes in the following manner:

Ci Co Control input and output

Zi Zo Isochronous input and output

Ii Io Interrupt input and output

Bi Bo Bulk input and output

The address information fields may contain leading zeros. If the bus is specified with -i, the Bus number field is redundant, but is kept for the ease of parsing.

- Status word. This word may have several fields, depending on the transfer type. Most transfers only have the status field. Interrupt and Isochronous transfers add an interval. For Isochronous, start frame and error count may be present. For callback and error events, the status field contains an integer number, which represents a "status" field of the URB. For a submission event, status makes no sense, so the field contains a single dash.

Control submissions are an exception, because they may have a setup packet. In such case, the event contains a letter in place of the status word. The letter is called "setup tag".

- Setup packet, if present, consists of 5 words: one of each for bmRequestType, bRequest, wValue, wIndex, wLength, as specified by the USB Specification 2.0. These words are safe to decode if Setup Tag was 's'. Otherwise, the setup packet was present, but not captured, and the fields contain filler.

- The number of isochronous frame descriptors (optional).

- Isochronous descriptors (optional). Like the "pipe word", each descriptor contains fields separated by colons: status, offset, and length.

- Data Tag

- Data (if Data Tag is '=')

Data stream and its ASCII representation follow on separate lines. Each line starts with a space for the ease of identification.

The following is the list of words for the legacy format, from left to right:

- URB Tag. This is normally a kernel mode address of the URB structure.

- Timestamp in microseconds, a decimal number. The timestamp's resolution depends on available clock, and so it can be much worse than a microsecond (if the implementation uses jiffies, for example). The number of microseconds is usually truncated, so it can wrap if usbmon runs long enough.

- Event Type. This type refers to the format of the event, not URB type. Available types are: S - submission, C - callback, E - submission error.

- "Pipe". The pipe concept is deprecated. This is a composite word, used to be derived from information in pipes. It consists of three fields, separated by colons: URB type and direction, Device address, Endpoint number. Type and direction are encoded with two bytes in the following manner:

Ci Co Control input and output

Zi Zo Isochronous input and output

Ii Io Interrupt input and output

Bi Bo Bulk input and output

Device address and Endpoint number are 3-digit and 2-digit (respectively) decimal numbers, with leading zeroes.

- URB Status. In most cases, this field contains a number, sometimes negative, which represents a "status" field of the URB. This field makes no sense for submissions, but is present anyway to help scripts with parsing. When an error occurs, the field contains the error code. In case of a submission of a Control packet, this field contains a Setup Tag instead of an error code. It is easy to tell whether the Setup Tag is present because it is never a number. Thus if scripts find a number in this field, they proceed to read Data Length. If they find something else, like a letter, they read the setup packet before reading the Data Length.

- Setup packet, if present, consists of 5 words: one of each for bmRequestType, bRequest, wValue, wIndex, wLength, as specified by the USB Specification 2.0. These words are safe to decode if Setup Tag was 's'. Otherwise, the setup packet was present, but not captured, and the fields contain filler.

- Data Length. For submissions, this is the requested length. For callbacks, this is the actual length.

- Data tag. The usbmon may not always capture data, even if length is nonzero. The data words are present only if this tag is '='.

- Data words follow, in big endian hexadecimal format. Notice that they are not machine words, but really just a byte stream split into words to make it easier to read. Thus, the last word may contain from one to four bytes. The length of collected data is limited (see the -s parameter) and can be less than the data length report in the Data Length word.

## FILES
/proc/devices

This file is read to determine the major of /dev/usbmonN if such node does not exist in the system.

/dev/usbmonN

The usbmon attempts to open /dev/usbmon{N}, where N is the bus number. If the node does not exist, usbmon creates it.

## SEE ALSO
lsusb(8)

## AUTHOR
Pete Zaitcev, <zaitcev@redhat.com>.


usbmuxd

package: usbmuxd

title: usbmuxd(8)

text:
# usbmuxd(8)

## NAME
usbmuxd - Expose a socket to multiplex connections from and to iOS devices.

## SYNOPSIS
usbmuxd [OPTIONS]

## DESCRIPTION
usbmuxd stands for "USB multiplexing daemon". This daemon is in charge of multiplexing connections over USB to an iOS device. To users, it means you can sync your music, contacts, photos, etc. over USB. To developers, it means you can connect to any listening localhost socket on the device. usbmuxd is not used for tethering data transfer which uses a dedicated USB interface as a virtual network device. Multiple connections to different TCP ports can happen in parallel. The higher-level layers are handled by libimobiledevice.

When usbmuxd is running (normally started, or stopped as a result of "udev" auto-insertion messages or by systemd) it provides a socket interface in "/var/run/usbmuxd" that is designed to be compatible with the socket interface that is provided on Mac OS X.

You should also create a "usbmux" user that has access to USB devices on your system. Alternatively, you can pass a different username using the -U argument.

Due to iOS 7 the daemon now also manages pairing records with iOS devices and the host in "/var/lib/lockdown" (Linux) or "/var/db/lockdown" (Mac OS X). Ensure proper permissions are setup for the daemon to access the directory.

## OPTIONS
-U, --user USER

Change to this user after startup (needs USB privileges).

-f, --foreground

Do not daemonize (implies one -v).

-n, --disable-hotplug

Disables automatic discovery of devices on hotplug. Starting another instance will trigger discovery instead.

-z, --enable-exit

Enable "--exit" request from other instances and exit automatically if no device is attached.

-u, --udev

Run in udev operation mode (implies -n and -z).

-s, --systemd

Run in systemd operation mode (implies -z and -f).

-x, --exit

Notify a running instance to exit if there are no devices connected (sends SIGUSR1 to running instance) and exit.

-X, --force-exit

Notify a running instance to exit even if there are still devices connected (always works) and exit.

-v, --verbose

be verbose (use twice or more to increase verbose level).

-V, --version

print version information and exit.

-h, --help

prints usage information.

## AUTHOR
The first usbmuxd daemon implementation was authored by Hector Martin.

Now mainly developed by Nikias Bassen, Martin Szulecki and contributors (see AUTHORS file).

## SEE ALSO
idevice_id(1), iproxy(1).

## ON THE WEB
https://libimobiledevice.org

https://github.com/libimobiledevice/usbmuxd


lsusb

package: usbutils

title: lsusb(8)

summary: list USB devices

text:
# lsusb(8)

## NAME
lsusb - list USB devices

## SYNOPSIS
lsusb [ options ]

## DESCRIPTION
lsusb is a utility for displaying information about USB buses in the system and the devices connected to them. It uses udev's hardware database to associate a full human-readable name to the vendor ID and the product ID.

## OPTIONS
-v, --verbose

Tells lsusb to be verbose and display detailed information about the devices shown. This includes configuration descriptors for the device's current speed. Class descriptors will be shown, when available, for USB device classes including hub, audio, HID, communications, and chipcard. Can be used with the t option.

-s [[bus]:][devnum]

Show only devices in specified bus and/or devnum. Both IDs are given in decimal and may be omitted.

-d [vendor]:[product]

Show only devices with the specified vendor and product ID. Both IDs are given in hexadecimal.

-D device

Do not scan the /dev/bus/usb directory, instead display only information about the device whose device file is given. The device file should be something like /dev/bus/usb/001/001. This option displays detailed information like the v option; you must be root to do this.

-t, --tree

Tells lsusb to dump the physical USB device hierarchy as a tree. Verbosity can be increased twice with the v option.

-V, --version

Print version information on standard output, then exit successfully.

## RETURN VALUE
If the specified device is not found, a non-zero exit code is returned.

## SEE ALSO
lspci(8), usbview(8).

## AUTHOR
Thomas Sailer, <sailer@ife.ee.ethz.ch>.


usbhid-dump

title: usbhid-dump(8)

text:
# usbhid-dump(8)

## NAME
usbhid-dump - dump USB HID device report descriptors and streams

## SYNOPSIS
usbhid-dump [OPTION]...

## DESCRIPTION
usbhid-dump uses libusb to dump report descriptors and streams from HID (human interface device) interfaces of USB devices. By default, it dumps HID interfaces of all connected USB devices, but could be limited to a subset of them, or to a single interface, using options.

NOTE: usbhid-dump detaches kernel drivers from the interfaces it dumps and uses them exclusively, so no other program receives the input in the meantime. The report descriptor dumping is instantaneous, but the stream dumping continues until terminated with SIGINT (^C from the terminal) or a timeout expires.

If you accidentally start dumping a stream from the USB keyboard you use to control the terminal, the system will stop receiving the input and you won't be able to terminate usbhid-dump. Just stop your input and wait until the timeout expires. The stream dumping will stop, the keyboard will be reattached to the kernel driver and you will regain control.

The default stream dumping timeout is 60 seconds and could be changed with the -t option.

## OPTIONS
-h, --help

Output a help message and exit.

-v, --version

Output version information and exit.

-s, -a, --address=bus[:dev]

Limit interfaces by bus number and device address. Both 1-255, decimal. Zeroes match any bus or device.

-d, -m, --model=vid[:pid]

Limit interfaces by device vendor and product IDs. Both 1-FFFF, hexadecimal. Zeroes match any vendor or product.

-i, --interface=NUMBER

Limit interfaces by number (0-254), decimal. 255 matches any interface.

-e, --entity=STRING

The entity to dump: either "descriptor", "stream" or "all". The value can be abbreviated down to one letter. The default is "descriptor".

-t, --stream-timeout=NUMBER

Stream interrupt transfer timeout, ms. Zero means infinity. The default is 60000 (60 seconds).

-p, --stream-paused

Start with the stream dump output paused.

-f, --stream-feedback

Enable stream dumping feedback: print a dot to stderr for every transfer dumped.

## SIGNALS
USR1/USR2

Pause/resume stream dump output.

## OUTPUT FORMAT
usbhid-dump outputs dumps in chunks. Each chunk is separated by an empty line and starts with the following header line:

BUS:DEVICE:INTERFACE:ENTITY TIMESTAMP

Here, BUS, DEVICE and INTERFACE are bus, device and interface numbers respectively. ENTITY is either "DESCRIPTOR" or "STREAM". TIMESTAMP is timestamp in seconds since epoch.

After the header the actual dump data follows as hex bytes. A descriptor chunk includes the whole report descriptor. Every stream chunk includes a whole report, usually, but if a report is bigger than endpoint's wMaxPacketSize, it will span several chunks.

## EXAMPLES
Dump report descriptor for a device with address 3 on bus number 2:

usbhid-dump -a 2:3

Dump report stream for a device with vendor ID 0x5543 and product ID 0x0005:

usbhid-dump -m 5543:0005 -es

Dump report descriptor from interface 1 of a device with vendor ID 0x5543:

usbhid-dump -m 5543 -i 1 -ed

Dump report streams from all HID interfaces of all USB devices (caution: you will lose control over the terminal if you use USB keyboard):

usbhid-dump -es

## AUTHOR
Nikolai Kondrashov <spbnick@gmail.com>


usbview

package: usbview

title: usbview(8)

summary: display information on USB devices

text:
# usbview(8)

## NAME
usbview - display information on USB devices

## SYNOPSIS
usbview

## DESCRIPTION
usbview provides a graphical summary of USB devices connected to the system. Detailed information may be displayed by selecting individual devices in the tree display. Red items are those that have no driver associated with them.

## OPTIONS
No command line options are accepted by usbview.

## FILES
/sys/kernel/debug/usb/devices

Kernel file providing information on USB devices attached to the machine.

## SEE ALSO
lsusb(8), lspci(8).

## AUTHOR
usbview was written by Greg Kroah-Hartman <greg@kroah.com>. This manual page was written by Mark Brown <broonie@sirena.org.uk>, for the Debian GNU/Linux system (but may be used freely by others).


utftpd

package: utftpd

title: utftpd(8)

text:
# utftpd(8)

## NAME
utftpd - a trivial file transfer protocol (TFTP) server

## SYNOPSIS
utftp [options] [dirs]

## DESCRIPTION
utftpd sends and receives files with the TFTP protocol. It is normally started from inetd.

TFTP doesn't support authentication, so the only way to authenticate TFTP clients is by using IP addresses.

traditional TFTP access control

In traditional mode utftpd will allow access to files in all directories (and subdirectories of those) named one the command line. Read access will be allowed for all publicly readable files and write access to already existing and publicy writable files. Unlike other TFTP servers utftpd will deny all access if no directories have been specified on the command line. If you wish to sacrifice all security you can still specify a single slash character.

traditional mode access control summary

This means that every host which can talk to the TFTP server can read and write all those files, and of course every user on that hosts can do that, too. Therefore you should protect those TFTP servers with tcpd or a packet filter. There is no client-specific access control in this mode: all clients get the same rights.

relative filenames in traditional mode

are allowed for read accesses only. If utftpd sees a relative file name it qualifies it with a eventual value of the --global-chdir option, if any, and then tries to find the file in any of the directories named on the command line. It will stop at the first file. If that happens to be unreadable it will deny access.

extended access control

utftpd also offers a more elaborate access control scheme, which will be used if the --config-file option is given, and which allows to assign rights to read, create or overwrite files or files in directories for every single client. It also allows version control. Details may be found in in the utftpd.conf and utftpd_make manual pages.

## OPTIONS
-c, --config-file FILE

Use FILE as configuration file. This has to be a cdb database file. See the utftpd_make manual page for how to generate this file, and the utftpd.conf.5 manual page more information about the input file format of utftpd_make. This file may reside outside the chroot()ed area (this also means the filename should be relative to the real root directory). If this option is missing utftpd will fall back to old style compatibility, see above.

-C, --global-chroot DIR

utftpd shall change its working directory to DIR, and invoke chroot(".") magic after that. This will be done before the configuration file is read.

-d, --global-chdir DIR

utftpd shall change its working directory to DIR. This is done after a global chroot (see the -C option above).

-u, --global-uid NAME_OR_NUMBER

utftpd shall change its user ID to NAME_OR_NUMBER, which may be a number or a name. In case of a name it will be resolved at the start of utftpd. The change to the new user id will be done after a possible global chroot. You may specify a group as well: Use the USER.GROUP form for that (or leave out the USER to change only the group).

-v, --verbose

Be verbose (to syslog).

In case i screwed something up: short options use the same arguments as the long ones

## ORDER
utftpd will, upon startup, in that order:

receive the first packet from remote (it needs the address of the peer, to find his data in the configuration file). [just for the records: it can't use MSG_PEEK here because that would make inetd dance wild. Uah.] This needs to be done here and now simply because this packet has to be read, else awful things happen if utftpd exits before it reads the first packet.

open a syslog connection

open the configuration file, so it may reside outside the chrooted() area (see the --config-file option). This step is not done in traditional mode.

resolve user / group names from a --global-uid option.

chdir and then chroot to the --global-chroot directory, if given.

change user/group IDs to the --global-uid values, if any.

chdir to the --global-chdir directory, if given.

read the configuration file see the --config-file option. This step is only done if a configuration file has been given on the command line.

close the configuration file This step is only done if a configuration file has been given on the command line.

go to daemon mode: fork itself in the background

## VERSION CONTROL
utftpd knows about version control. If it's activated in the configuration file and the requested file has been put under version control (which you have to do yourself) then utftpd will

on GET requests (RRQ) try to check out the latest revision and send that. It will never care about checked out copies it finds lying around.

on PUT requests (WRQ) out an editable copy, receive the file and then check them in. It will deny access if the checkout fails. This behaviour allows you to manually check out a file, edit it, check it in again, without having to fear that utftpd overwrites the file you are editing, and is also the right way to not open a race condition (think of two clients wanting to write the same file, although this is a stupid thing to do anyway).

SCCS is preferred over RCS.

It's a usually not a bright idea to put binary files under revision control: VC systems tend to dislike them. Some implementations may be ok, so GNU RCS seems to work find, provided it also has GNU diff available.

Version control support is not available in traditional access control mode.

## SEE ALSO
utftpd_make(8), utftpd.conf(5), RFC 1350, RFC 2348, RFC 2349.


title: utftpd_make(8)

summary: compile rules for utftpd

text:
# utftpd_make(8)

## NAME
utftpd_make - compile rules for utftpd

## SYNOPSIS
utftpd_make cdb-file tmp-file [input-file]

## DESCRIPTION
utftpd_make compiles rules from a human readable format to a database file which may be used by utftpd. The standard input will be read if input-file is not given.

tmp-file and cdb-file have to be located on the same filesystem.

utftpd_make updates cdb-file atomically: you may use it even if utftpd is running.

## SEE ALSO
utftpd(8), utftpd.conf(5), RFC 1350.


blkdiscard

package: util-linux

title: blkdiscard(8)

summary: discard sectors on a device

text:
# blkdiscard(8)

## NAME
blkdiscard - discard sectors on a device

## SYNOPSIS
blkdiscard [options] [-o offset] [-l length] device

## DESCRIPTION
blkdiscard is used to discard device sectors. This is useful for solid-state drivers (SSDs) and thinly-provisioned storage. Unlike fstrim(8), this command is used directly on the block device.

By default, blkdiscard will discard all blocks on the device. Options may be used to modify this behavior based on range or size, as explained below.

The device argument is the pathname of the block device.

WARNING: All data in the discarded region on the device will be lost!

## OPTIONS
The offset and length arguments may be followed by the multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB") or the suffixes KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.

-f, --force

Disable all checking. Since v2.36 the block device is open in exclusive mode (O_EXCL) by default to avoid collision with mounted filesystem or another kernel subsystem. The --force option disables the exclusive access mode.

-o, --offset offset

Byte offset into the device from which to start discarding. The provided value must be aligned to the device sector size. The default value is zero.

-l, --length length

The number of bytes to discard (counting from the starting point). The provided value must be aligned to the device sector size. If the specified value extends past the end of the device, blkdiscard will stop at the device size boundary. The default value extends to the end of the device.

-p, --step length

The number of bytes to discard within one iteration. The default is to discard all by one ioctl call.

-q, --quiet

Suppress warning messages.

-s, --secure

Perform a secure discard. A secure discard is the same as a regular discard except that all copies of the discarded blocks that were possibly created by garbage collection must also be erased. This requires support from the device.

-z, --zeroout

Zero-fill rather than discard.

-v, --verbose

Display the aligned values of offset and length. If the --step option is specified, it prints the discard progress every second.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## EXIT STATUS
blkdiscard has the following exit status values:

0

success

1

failure; incorrect invocation, permissions or any other generic error

2

failure; since v2.39, the device does not support discard operation

## AUTHORS
Lukas Czerner <lczerner@redhat.com>, Karel Zak <kzak@redhat.com>

## SEE ALSO
fstrim(8)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The blkdiscard command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


blkid

title: blkid(8)

summary: locate/print block device attributes

text:
# blkid(8)

## NAME
blkid - locate/print block device attributes

## SYNOPSIS
blkid --label label | --uuid uuid

blkid [--no-encoding --garbage-collect --list-one --cache-file file] [--output format] [--match-tag tag] [--match-token NAME=value] [device...]

blkid --probe [--offset offset] [--output format] [--size size] [--match-tag tag] [--match-types list] [--usages list] [--no-part-details] device...

blkid --info [--output format] [--match-tag tag] device...

## DESCRIPTION
The blkid program is the command-line interface to working with the libblkid(3) library. It can determine the type of content (e.g., filesystem or swap) that a block device holds, and also the attributes (tokens, NAME=value pairs) from the content metadata (e.g., LABEL or UUID fields).

It is recommended to use lsblk(8) command to get information about block devices, or lsblk --fs to get an overview of filesystems, or findmnt(8) to search in already mounted filesystems.

lsblk(8) provides more information, better control on output formatting, easy to use in scripts and it does not require root permissions to get actual information. blkid reads information directly from devices and for non-root users it returns cached unverified information. blkid is mostly designed for system services and to test libblkid(3) functionality.

When device is specified, tokens from only this device are displayed. It is possible to specify multiple device arguments on the command line. If none is given, all partitions or unpartitioned devices which appear in /proc/partitions are shown, if they are recognized.

blkid has two main forms of operation: either searching for a device with a specific NAME=value pair, or displaying NAME=value pairs for one or more specified devices.

For security reasons blkid silently ignores all devices where the probing result is ambivalent (multiple colliding filesystems are detected). The low-level probing mode (-p) provides more information and extra exit status in this case. It’s recommended to use wipefs(8) to get a detailed overview and to erase obsolete stuff (magic strings) from the device.

## OPTIONS
The size and offset arguments may be followed by the multiplicative suffixes like KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB"), or the suffixes KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.

-c, --cache-file cachefile

Read from cachefile instead of reading from the default cache file (see the CONFIGURATION FILE section for more details). If you want to start with a clean cache (i.e., don’t report devices previously scanned but not necessarily available at this time), specify /dev/null.

-d, --no-encoding

Don’t encode non-printing characters. The non-printing characters are encoded by ^ and M- notation by default. Note that the --output udev output format uses a different encoding which cannot be disabled.

-D, --no-part-details

Don’t print information (PART_ENTRY_* tags) from partition table in low-level probing mode.

-g, --garbage-collect

Perform a garbage collection pass on the blkid cache to remove devices which no longer exist.

-H, --hint setting

Set probing hint. The hints are an optional way to force probing functions to check, for example, another location. The currently supported is "session_offset=number" to set session offset on multi-session UDF.

-i, --info

Display information about I/O Limits (aka I/O topology). The 'export' output format is automatically enabled. This option can be used together with the --probe option.

-k, --list-filesystems

List all known filesystems and RAIDs and exit.

-l, --list-one

Look up only one device that matches the search parameter specified with the --match-token option. If there are multiple devices that match the specified search parameter, then the device with the highest priority is returned, and/or the first device found at a given priority (but see below note about udev). Device types in order of decreasing priority are: Device Mapper, EVMS, LVM, MD, and finally regular block devices. If this option is not specified, blkid will print all of the devices that match the search parameter. This option forces blkid to use udev when used for LABEL or UUID tokens in --match-token. The goal is to provide output consistent with other utils (like mount(8), etc.) on systems where the same tag is used for multiple devices.

-L, --label label

Look up the device that uses this filesystem label; this is equal to --list-one --output device --match-token LABEL=label. This lookup method is able to reliably use /dev/disk/by-label udev symlinks (dependent on a setting in /etc/blkid.conf). Avoid using the symlinks directly; it is not reliable to use the symlinks without verification. The --label option works on systems with and without udev. Unfortunately, the original blkid(8) from e2fsprogs uses the -L option as a synonym for -o list. For better portability, use -l -o device -t LABEL=label and -o list in your scripts rather than the -L option.

-n, --match-types list

Restrict the probing functions to the specified (comma-separated) list of superblock types (names). The list items may be prefixed with "no" to specify the types which should be ignored. For example: blkid --probe --match-types vfat,ext3,ext4 /dev/sda1

probes for vfat, ext3 and ext4 filesystems, and

blkid --probe --match-types nominix /dev/sda1

probes for all supported formats except minix filesystems. This option is only useful together with --probe.

-o, --output format

Use the specified output format. Note that the order of variables and devices is not fixed. See also option -s. The format parameter may be: full

print all tags (the default)

value

print the value of the tags

list

print the devices in a user-friendly format; this output format is unsupported for low-level probing (--probe or --info). This output format is DEPRECATED in favour of the lsblk(8) command.

device

print the device name only; this output format is always enabled for the --label and --uuid options

udev

print key="value" pairs for easy import into the udev environment; the keys are prefixed by ID_FS_ or ID_PART_ prefixes. The value may be modified to be safe for udev environment; allowed is plain ASCII, hex-escaping and valid UTF-8, everything else (including whitespaces) is replaced with '_'. The keys with _ENC postfix use hex-escaping for unsafe chars. The udev output returns the ID_FS_AMBIVALENT tag if more superblocks are detected, and ID_PART_ENTRY_* tags are always returned for all partitions including empty partitions.

This output format is DEPRECATED.

export

print key=value pairs for easy import into the environment; this output format is automatically enabled when I/O Limits (--info option) are requested. The non-printing characters are encoded by ^ and M- notation and all potentially unsafe characters are escaped.

-O, --offset offset

Probe at the given offset (only useful with --probe). This option can be used together with the --info option.

-p, --probe

Switch to low-level superblock probing mode (bypassing the cache). Note that low-level probing also returns information about partition table type (PTTYPE tag) and partitions (PART_ENTRY_* tags). The tag names produced by low-level probing are based on names used internally by libblkid and it may be different than when executed without --probe (for example PART_ENTRY_UUID= vs PARTUUID=). See also --no-part-details.

-s, --match-tag tag

For each (specified) device, show only the tags that match tag. It is possible to specify multiple --match-tag options. If no tag is specified, then all tokens are shown for all (specified) devices. In order to just refresh the cache without showing any tokens, use --match-tag none with no other options.

-S, --size size

Override the size of device/file (only useful with --probe).

-t, --match-token NAME=value

Search for block devices with tokens named NAME that have the value value, and display any devices which are found. Common values for NAME include TYPE, LABEL, and UUID. If there are no devices specified on the command line, all block devices will be searched; otherwise only the specified devices are searched.

-u, --usages list

Restrict the probing functions to the specified (comma-separated) list of "usage" types. Supported usage types are: filesystem, raid, crypto and other. The list items may be prefixed with "no" to specify the usage types which should be ignored. For example: blkid --probe --usages filesystem,other /dev/sda1

probes for all filesystem and other (e.g., swap) formats, and

blkid --probe --usages noraid /dev/sda1

probes for all supported formats except RAIDs. This option is only useful together with --probe.

-U, --uuid uuid

Look up the device that uses this filesystem uuid. For more details see the --label option.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## EXIT STATUS
If the specified device or device addressed by specified token (option --match-token) was found and it’s possible to gather any information about the device, an exit status 0 is returned. Note the option --match-tag filters output tags, but it does not affect exit status.

If the specified token was not found, or no (specified) devices could be identified, or it is impossible to gather any information about the device identifiers or device content an exit status of 2 is returned.

For usage or other errors, an exit status of 4 is returned.

If an ambivalent probing result was detected by low-level probing mode (-p), an exit status of 8 is returned.

## CONFIGURATION FILE
The standard location of the /etc/blkid.conf config file can be overridden by the environment variable BLKID_CONF. The following options control the libblkid library:

SEND_UEVENT=<yes|not>

Sends uevent when /dev/disk/by-{label,uuid,partuuid,partlabel}/ symlink does not match with LABEL, UUID, PARTUUID or PARTLABEL on the device. Default is "yes".

CACHE_FILE=<path>

Overrides the standard location of the cache file. This setting can be overridden by the environment variable BLKID_FILE. Default is /run/blkid/blkid.tab, or /etc/blkid.tab on systems without a /run directory.

EVALUATE=<methods>

Defines LABEL and UUID evaluation method(s). Currently, the libblkid library supports the "udev" and "scan" methods. More than one method may be specified in a comma-separated list. Default is "udev,scan". The "udev" method uses udev /dev/disk/by-* symlinks and the "scan" method scans all block devices from the /proc/partitions file.

## ENVIRONMENT
Setting LIBBLKID_DEBUG=all enables debug output.

## AUTHORS
blkid was written by Andreas Dilger for libblkid and improved by Theodore Ts’o and Karel Zak.

## SEE ALSO
libblkid(3), findfs(8), lsblk(8), wipefs(8)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The blkid command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


blkpr

title: blkpr(8)

text:
# blkpr(8)

## NAME
blkpr - run persistent reservations command on a device

## SYNOPSIS
blkpr [options] device

## DESCRIPTION
blkpr is used to run persistent reservations command on device that supports Persistent Reservations feature.

The device argument is the pathname of the block device.

## OPTIONS
-c, --command command

The command of persistent reservations, supported commands are register, reserve, release, preempt, preempt-abort, and clear.

-k, --key key

The key the command should operate on.

-K, --oldkey oldkey

The old key the command should operate on.

-f, --flag flag

Supported flag is ignore-key.

-t, --type type

Supported types are write-exclusive, exclusive-access, write-exclusive-reg-only, exclusive-access-reg-only, write-exclusive-all-regs, and exclusive-access-all-regs.

-V, --version

Display version information and exit.

-h, --help

Display help text and exit.

## AUTHORS
zhenwei pi <pizhenwei@bytedance.com>

## SEE ALSO
sg_persist(8)

Linux documentation at: <https://docs.kernel.org/block/pr.html> iSCSI specification at: <https://datatracker.ietf.org/doc/html/rfc3720> NVMe-oF specification at: <https://nvmexpress.org/nvme-over-fabrics-part-two/>

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The blkpr command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


blkzone

title: blkzone(8)

summary: run zone command on a device

text:
# blkzone(8)

## NAME
blkzone - run zone command on a device

## SYNOPSIS
blkzone command [options] device

## DESCRIPTION
blkzone is used to run zone command on device that support the Zoned Block Commands (ZBC) or Zoned-device ATA Commands (ZAC). The zones to operate on can be specified using the offset, count and length options.

The device argument is the pathname of the block device.

## COMMANDS

### report
The command blkzone report is used to report device zone information.

By default, the command will report all zones from the start of the block device. Options may be used to modify this behavior, changing the starting zone or the size of the report, as explained below.

Report output:

start

Zone start sector

len

Zone length in number of sectors

cap

Zone capacity in number of sectors

wptr

Zone write pointer position

reset

Reset write pointer recommended

non-seq

Non-sequential write resources active

cond

Zone condition

type

Zone type

Zone conditions:

cl

Closed

nw

Not write pointer

em

Empty

fu

Full

oe

Explicitly opened

oi

Implicitly opened

ol

Offline

ro

Read only

x?

Reserved conditions (should not be reported)

### capacity
The command blkzone capacity is used to report device capacity information.

By default, the command will report the sum, in number of sectors, of all zone capacities on the device. Options may be used to modify this behavior, changing the starting zone or the size of the report, as explained below.

### reset
The command blkzone reset is used to reset one or more zones. Unlike sg_reset_wp(8), this command operates from the block layer and can reset a range of zones.

### open
The command blkzone open is used to explicitly open one or more zones. Unlike sg_zone(8), open action, this command operates from the block layer and can open a range of zones.

### close
The command blkzone close is used to close one or more zones. Unlike sg_zone(8), close action, this command operates from the block layer and can close a range of zones.

### finish
The command blkzone finish is used to finish (transition to full condition) one or more zones. Unlike sg_zone(8), finish action, this command operates from the block layer and can finish a range of zones.

By default, the reset, open, close and finish commands will operate from the zone at device sector 0 and operate on all zones. Options may be used to modify this behavior as explained below.

## OPTIONS
The offset and length option arguments may be followed by the multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB") or the suffixes KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB. Additionally, the 0x prefix can be used to specify offset and length in hex.

-o, --offset sector

The starting zone specified as a sector offset. The provided offset in sector units (512 bytes) should match the start of a zone. The default value is zero.

-l, --length sectors

The maximum number of sectors the command should operate on. The default value is the number of sectors remaining after offset. This option cannot be used together with the option --count.

-c, --count count

The maximum number of zones the command should operate on. The default value is the number of zones starting from offset. This option cannot be used together with the option --length.

-f, --force

Enforce commands to change zone status on block devices used by the system.

-v, --verbose

Display the number of zones returned in the report or the range of sectors reset.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## AUTHORS
Shaun Tancheff <shaun@tancheff.com>, Karel Zak <kzak@redhat.com>

## SEE ALSO
sg_rep_zones(8)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The blkzone command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


blockdev

title: blockdev(8)

text:
# blockdev(8)

## NAME
blockdev - call block device ioctls from the command line

## SYNOPSIS
blockdev [-q] [-v] command [command...] device [device...]

blockdev --report [device...]

blockdev -h|-V

## DESCRIPTION
The utility blockdev allows one to call block device ioctls from the command line.

## OPTIONS
-q

Be quiet.

-v

Be verbose.

--report

Print a report for the specified device. It is possible to give multiple devices. If none is given, all devices which appear in /proc/partitions are shown. Note that the partition StartSec is in 512-byte sectors.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## COMMANDS
It is possible to give multiple devices and multiple commands.

--flushbufs

Flush buffers.

--getalignoff

Get alignment offset.

--getbsz

Print the blocksize in bytes. This size does not describe device topology. It’s the size used internally by the kernel and it may be modified (for example) by filesystem driver on mount.

--getdiscardzeroes

Get discard zeroes support status.

--getdiskseq

Get disk sequence number.

--getfra

Get filesystem readahead in 512-byte sectors.

--getiomin

Get minimum I/O size.

--getioopt

Get optimal I/O size.

--getmaxsect

Get max sectors per request.

--getpbsz

Get physical block (sector) size.

--getra

Print readahead (in 512-byte sectors).

--getro

Get read-only. Print 1 if the device is read-only, 0 otherwise.

--getsize64

Print device size in bytes.

--getsize

Print device size (32-bit!) in sectors. Deprecated in favor of the --getsz option.

--getss

Print logical sector size in bytes - usually 512.

--getsz

Get size in 512-byte sectors.

--rereadpt

Reread partition table

--setbsz bytes

Set blocksize. Note that the block size is specific to the current file descriptor opening the block device, so the change of block size only persists for as long as blockdev has the device open, and is lost once blockdev exits.

--setfra sectors

Set filesystem readahead (same as --setra on 2.6 kernels).

--setra sectors

Set readahead (in 512-byte sectors).

--setro

Set read-only. The currently active access to the device may not be affected by the change. For example, a filesystem already mounted in read-write mode will not be affected. The change applies after remount.

--setrw

Set read-write.

## AUTHORS
blockdev was written by Andries E. Brouwer and rewritten by Karel Zak.

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The blockdev command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


chcpu

title: chcpu(8)

summary: configure CPUs

text:
# chcpu(8)

## NAME
chcpu - configure CPUs

## SYNOPSIS
chcpu -c|-d|-e|-g cpu-list

chcpu -p mode

chcpu -r|-h|-V

## DESCRIPTION
chcpu can modify the state of CPUs. It can enable or disable CPUs, scan for new CPUs, change the CPU dispatching mode of the underlying hypervisor, and request CPUs from the hypervisor (configure) or return CPUs to the hypervisor (deconfigure).

Some options have a cpu-list argument. Use this argument to specify a comma-separated list of CPUs. The list can contain individual CPU addresses or ranges of addresses. For example, 0,5,7,9-11 makes the command applicable to the CPUs with the addresses 0, 5, 7, 9, 10, and 11.

## OPTIONS
-c, --configure cpu-list

Configure the specified CPUs. Configuring a CPU means that the hypervisor takes a CPU from the CPU pool and assigns it to the virtual hardware on which your kernel runs.

-d, --disable cpu-list

Disable the specified CPUs. Disabling a CPU means that the kernel sets it offline.

-e, --enable cpu-list

Enable the specified CPUs. Enabling a CPU means that the kernel sets it online. A CPU must be configured, see -c, before it can be enabled.

-g, --deconfigure cpu-list

Deconfigure the specified CPUs. Deconfiguring a CPU means that the hypervisor removes the CPU from the virtual hardware on which the Linux instance runs and returns it to the CPU pool. A CPU must be offline, see -d, before it can be deconfigured.

-p, --dispatch mode

Set the CPU dispatching mode (polarization). This option has an effect only if your hardware architecture and hypervisor support CPU polarization. Available modes are: horizontal

The workload is spread across all available CPUs.

vertical

The workload is concentrated on few CPUs.

-r, --rescan

Trigger a rescan of CPUs. After a rescan, the Linux kernel recognizes the new CPUs. Use this option on systems that do not automatically detect newly attached CPUs.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## EXIT STATUS
chcpu has the following exit status values:

0

success

1

failure

64

partial success

## AUTHORS
Heiko Carstens <heiko.carstens@de.ibm.com>

## COPYRIGHT
Copyright IBM Corp. 2011

## SEE ALSO
lscpu(1)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The chcpu command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


chmem

title: chmem(8)

summary: configure memory

text:
# chmem(8)

## NAME
chmem - configure memory

## SYNOPSIS
chmem [-h] [-V*] [-v] [-e|-d] [SIZE|RANGE -b BLOCKRANGE] [-z ZONE]

## DESCRIPTION
The chmem command sets a particular size or range of memory online or offline.

•Specify SIZE as <size>[m|M|g|G]. With m or M, <size> specifies the memory size in MiB (1024 x 1024 bytes). With g or G, <size> specifies the memory size in GiB (1024 x 1024 x 1024 bytes). The default unit is MiB.

•Specify RANGE in the form 0x<start>-0x<end> as shown in the output of the lsmem(1) command. <start> is the hexadecimal address of the first byte and <end> is the hexadecimal address of the last byte in the memory range.

•Specify BLOCKRANGE in the form <first>-<last> or <block> as shown in the output of the lsmem(1) command. <first> is the number of the first memory block and <last> is the number of the last memory block in the memory range. Alternatively a single block can be specified. BLOCKRANGE requires the --blocks option.

•Specify ZONE as the name of a memory zone, as shown in the output of the lsmem -o +ZONES command. The output shows one or more valid memory zones for each memory range. If multiple zones are shown, then the memory range currently belongs to the first zone. By default, chmem will set memory online to the zone Movable, if this is among the valid zones. This default can be changed by specifying the --zone option with another valid zone. For memory ballooning, it is recommended to select the zone Movable for memory online and offline, if possible. Memory in this zone is much more likely to be able to be offlined again, but it cannot be used for arbitrary kernel allocations, only for migratable pages (e.g., anonymous and page cache pages). Use the --help option to see all available zones.

SIZE and RANGE must be aligned to the Linux memory block size, as shown in the output of the lsmem(1) command.

Setting memory online can fail for various reasons. On virtualized systems it can fail if the hypervisor does not have enough memory left, for example because memory was overcommitted. Setting memory offline can fail if Linux cannot free the memory. If only part of the requested memory can be set online or offline, a message tells you how much memory was set online or offline instead of the requested amount.

When setting memory online chmem starts with the lowest memory block numbers. When setting memory offline chmem starts with the highest memory block numbers.

## OPTIONS
-b, --blocks

Use a BLOCKRANGE parameter instead of RANGE or SIZE for the --enable and --disable options.

-d, --disable

Set the specified RANGE, SIZE, or BLOCKRANGE of memory offline.

-e, --enable

Set the specified RANGE, SIZE, or BLOCKRANGE of memory online.

-z, --zone

Select the memory ZONE where to set the specified RANGE, SIZE, or BLOCKRANGE of memory online or offline. By default, memory will be set online to the zone Movable, if possible.

-v, --verbose

Verbose mode. Causes chmem to print debugging messages about it’s progress.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## EXIT STATUS
chmem has the following exit status values:

0

success

1

failure

64

partial success

## EXAMPLE
chmem --enable 1024

This command requests 1024 MiB of memory to be set online.

chmem -e 2g

This command requests 2 GiB of memory to be set online.

chmem --disable 0x00000000e4000000-0x00000000f3ffffff

This command requests the memory range starting with 0x00000000e4000000 and ending with 0x00000000f3ffffff to be set offline.

chmem -b -d 10

This command requests the memory block number 10 to be set offline.

## SEE ALSO
lsmem(1)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The chmem command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


ctrlaltdel

title: ctrlaltdel(8)

summary: set the function of the Ctrl\-Alt\-Del combination

text:
# ctrlaltdel(8)

## NAME
ctrlaltdel - set the function of the Ctrl-Alt-Del combination

## SYNOPSIS
ctrlaltdel hard|soft

## DESCRIPTION
Based on examination of the linux/kernel/reboot.c code, it is clear that there are two supported functions that the <Ctrl-Alt-Del> sequence can perform.

hard

Immediately reboot the computer without calling sync(2) and without any other preparation. This is the default.

soft

Make the kernel send the SIGINT (interrupt) signal to the init process (this is always the process with PID 1). If this option is used, the init(8) program must support this feature. Since there are now several init(8) programs in the Linux community, please consult the documentation for the version that you are currently using.

When the command is run without any argument, it will display the current setting.

The function of ctrlaltdel is usually set in the /etc/rc.local file.

## OPTIONS
-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## FILES
/etc/rc.local

## AUTHORS
Peter Orbaek <poe@daimi.aau.dk>

## SEE ALSO
init(8), systemd(1)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The ctrlaltdel command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


findfs

title: findfs(8)

summary: find a filesystem by label or UUID

text:
# findfs(8)

## NAME
findfs - find a filesystem by label or UUID

## SYNOPSIS
findfs NAME=value

## DESCRIPTION
findfs will search the block devices in the system looking for a filesystem or partition with specified tag. The currently supported tags are:

LABEL=<label>

Specifies filesystem label.

UUID=<uuid>

Specifies filesystem UUID.

PARTUUID=<uuid>

Specifies partition UUID. This partition identifier is supported for example for GUID Partition Table (GPT) partition tables.

PARTLABEL=<label>

Specifies partition label (name). The partition labels are supported for example for GUID Partition Table (GPT) or MAC partition tables.

If the filesystem or partition is found, the device name will be printed on stdout.

The complete overview about filesystems and partitions you can get for example by

lsblk --fs

partx --show <disk>

blkid

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## EXIT STATUS
0

success

1

label or uuid cannot be found

2

usage error, wrong number of arguments or unknown option

## ENVIRONMENT
LIBBLKID_DEBUG=all

enables libblkid debug output.

## AUTHORS
findfs was originally written by Theodore Ts’o <tytso@mit.edu> and re-written for the util-linux package by Karel Zak <kzak@redhat.com>.

## SEE ALSO
blkid(8), lsblk(8), partx(8)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The findfs command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


findmnt

title: findmnt(8)

summary: find a filesystem

text:
# findmnt(8)

## NAME
findmnt - find a filesystem

## SYNOPSIS
findmnt [options]

findmnt [options] device|mountpoint

findmnt [options] [--source] device [--target path|--mountpoint mountpoint]

## DESCRIPTION
findmnt will list all mounted filesystems or search for a filesystem. The findmnt command is able to search in /etc/fstab, /etc/mtab or /proc/self/mountinfo. If device or mountpoint is not given, all filesystems are shown.

The device may be specified by device name, major:minor numbers, filesystem label or UUID, or partition label or UUID. Note that findmnt follows mount(8) behavior where a device name may be interpreted as a mountpoint (and vice versa) if the --target, --mountpoint or --source options are not specified.

The command-line option --target accepts any file or directory and then findmnt displays the filesystem for the given path.

The command prints all mounted filesystems in the tree-like format by default. The default output, is subject to change. So whenever possible, you should avoid using default output in your scripts. Always explicitly define expected columns by using --output columns-list in environments where a stable output is required.

The relationship between block devices and filesystems is not always one-to-one. The filesystem may use more block devices. This is why findmnt provides SOURCE and SOURCES (pl.) columns. The column SOURCES displays all devices where it is possible to find the same filesystem UUID (or another tag specified in fstab when executed with --fstab and --evaluate).

## OPTIONS
-A, --all

Disable all built-in filters and print all filesystems.

-a, --ascii

Use ascii characters for tree formatting.

-b, --bytes

Print the sizes in bytes rather than in a human-readable format. By default, the unit, sizes are expressed in, is byte, and unit prefixes are in power of 2^10 (1024). Abbreviations of symbols are exhibited truncated in order to reach a better readability, by exhibiting alone the first letter of them; examples: "1 KiB" and "1 MiB" are respectively exhibited as "1 K" and "1 M", then omitting on purpose the mention "iB", which is part of these abbreviations.

-C, --nocanonicalize

Do not canonicalize paths at all. This option affects the comparing of paths and the evaluation of tags (LABEL, UUID, etc.).

-c, --canonicalize

Canonicalize all printed paths.

--deleted

Print filesystems where target (mountpoint) is marked as deleted by kernel.

-D, --df

Imitate the output of df(1). This option is equivalent to -o SOURCE,FSTYPE,SIZE,USED,AVAIL,USE%,TARGET but excludes all pseudo filesystems. Use --all to print all filesystems.

-d, --direction word

The search direction, either forward or backward.

-e, --evaluate

Convert all tags (LABEL, UUID, PARTUUID, or PARTLABEL) to the corresponding device names for the SOURCE column. It’s an unusual situation, but the same tag may be duplicated (used for more devices). For this purpose, there is SOURCES (pl.) column. This column displays by multi-line cell all devices where the tag is detected by libblkid. This option makes sense for fstab only.

-F, --tab-file path

Search in an alternative file. If used with --fstab, --mtab or --kernel, then it overrides the default paths. If specified more than once, then tree-like output is disabled (see the --list option).

-f, --first-only

Print the first matching filesystem only.

-i, --invert

Invert the sense of matching.

-J, --json

Use JSON output format.

-k, --kernel

Search in /proc/self/mountinfo. The output is in the tree-like format. This is the default. The output contains only mount options maintained by kernel (see also --mtab).

-l, --list

Use the list output format. This output format is automatically enabled if the output is restricted by the -t, -O, -S or -T option and the option --submounts is not used or if more that one source file (the option -F) is specified.

-M, --mountpoint path

Explicitly define the mountpoint file or directory. See also --target.

-m, --mtab

Search in /etc/mtab. The output is in the list format by default (see --tree). The output may include user space mount options.

-N, --task tid

Use alternative namespace /proc/<tid>/mountinfo rather than the default /proc/self/mountinfo. If the option is specified more than once, then tree-like output is disabled (see the --list option). See also the unshare(1) command.

-n, --noheadings

Do not print a header line.

-O, --options list

Limit the set of printed filesystems. More than one option may be specified in a comma-separated list. The -t and -O options are cumulative in effect. It is different from -t in that each option is matched exactly; a leading no at the beginning does not have global meaning. The "no" can used for individual items in the list. The "no" prefix interpretation can be disabled by "+" prefix.

-o, --output list

Define output columns. See the --help output to get a list of the currently supported columns. The TARGET column contains tree formatting if the --list or --raw options are not specified. The default list of columns may be extended if list is specified in the format +list (e.g., findmnt -o +PROPAGATION).

--output-all

Output almost all available columns. The columns that require --poll are not included.

-P, --pairs

Produce output in the form of key="value" pairs. All potentially unsafe value characters are hex-escaped (\x<code>). See also option --shell.

-p, --poll[=list]

Monitor changes in the /proc/self/mountinfo file. Supported actions are: mount, umount, remount and move. More than one action may be specified in a comma-separated list. All actions are monitored by default. The time for which --poll will block can be restricted with the --timeout or --first-only options.

The standard columns always use the new version of the information from the mountinfo file, except the umount action which is based on the original information cached by findmnt. The poll mode allows using extra columns:

ACTION

mount, umount, move or remount action name; this column is enabled by default

OLD-TARGET

available for umount and move actions

OLD-OPTIONS

available for umount and remount actions

--pseudo

Print only pseudo filesystems.

--shadow

Print only filesystems over-mounted by another filesystem.

-R, --submounts

Print recursively all submounts for the selected filesystems. The restrictions defined by options -t, -O, -S, -T and --direction are not applied to submounts. All submounts are always printed in tree-like order. The option enables the tree-like output format by default. This option has no effect for --mtab or --fstab.

-r, --raw

Use raw output format. All potentially unsafe characters are hex-escaped (\x<code>).

--real

Print only real filesystems.

-S, --source spec

Explicitly define the mount source. Supported specifications are device, maj:min, LABEL=label, UUID=uuid, PARTLABEL=label and PARTUUID=uuid.

-s, --fstab

Search in /etc/fstab. The output is in the list format (see --list).

-T, --target path

Define the mount target. If path is not a mountpoint file or directory, then findmnt checks the path elements in reverse order to get the mountpoint (this feature is supported only when searching in kernel files and unsupported for --fstab). It’s recommended to use the option --mountpoint when checks of path elements are unwanted and path is a strictly specified mountpoint.

-t, --types list

Limit the set of printed filesystems. More than one type may be specified in a comma-separated list. The list of filesystem types can be prefixed with no to specify the filesystem types on which no action should be taken. For more details see mount(8).

--tree

Enable tree-like output if possible. The options is silently ignored for tables where is missing child-parent relation (e.g., fstab).

--shadowed

Print only filesystems over-mounted by another filesystem.

-U, --uniq

Ignore filesystems with duplicate mount targets, thus effectively skipping over-mounted mount points.

-u, --notruncate

Do not truncate text in columns. The default is to not truncate the TARGET, SOURCE, UUID, LABEL, PARTUUID, PARTLABEL columns. This option disables text truncation also in all other columns.

-v, --nofsroot

Do not print a [/dir] in the SOURCE column for bind mounts or btrfs subvolumes.

-w, --timeout milliseconds

Specify an upper limit on the time for which --poll will block, in milliseconds.

-x, --verify

Check mount table content. The default is to verify /etc/fstab parsability and usability. It’s possible to use this option also with --tab-file. It’s possible to specify source (device) or target (mountpoint) to filter mount table. The option --verbose forces findmnt to print more details.

--verbose

Force findmnt to print more information (--verify only for now).

--vfs-all

When used with VFS-OPTIONS column, print all VFS (fs-independent) flags. This option is designed for auditing purposes to list also default VFS kernel mount options which are normally not listed.

-y, --shell

The column name will be modified to contain only characters allowed for shell variable identifiers. This is usable, for example, with --pairs. Note that this feature has been automatically enabled for --pairs in version 2.37, but due to compatibility issues, now it’s necessary to request this behavior by --shell.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## EXIT STATUS
The exit value is 0 if there is something to display, or 1 on any error (for example if no filesystem is found based on the user’s filter specification, or the device path or mountpoint does not exist).

## ENVIRONMENT
LIBMOUNT_FSTAB=<path>

overrides the default location of the fstab file

LIBMOUNT_MTAB=<path>

overrides the default location of the mtab file

LIBMOUNT_DEBUG=all

enables libmount debug output

LIBSMARTCOLS_DEBUG=all

enables libsmartcols debug output

LIBSMARTCOLS_DEBUG_PADDING=on

use visible padding characters.

## EXAMPLES
findmnt --fstab -t nfs

Prints all NFS filesystems defined in /etc/fstab.

findmnt --fstab /mnt/foo

Prints all /etc/fstab filesystems where the mountpoint directory is /mnt/foo. It also prints bind mounts where /mnt/foo is a source.

findmnt --fstab --target /mnt/foo

Prints all /etc/fstab filesystems where the mountpoint directory is /mnt/foo.

findmnt --fstab --evaluate

Prints all /etc/fstab filesystems and converts LABEL= and UUID= tags to the real device names.

findmnt -n --raw --evaluate --output=target LABEL=/boot

Prints only the mountpoint where the filesystem with label "/boot" is mounted.

findmnt --poll --mountpoint /mnt/foo

Monitors mount, unmount, remount and move on /mnt/foo.

findmnt --poll=umount --first-only --mountpoint /mnt/foo

Waits for /mnt/foo unmount.

findmnt --poll=remount -t ext3 -O ro

Monitors remounts to read-only mode on all ext3 filesystems.

## AUTHORS
Karel Zak <kzak@redhat.com>

## SEE ALSO
fstab(5), mount(8)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The findmnt command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


fsck

title: fsck(8)

summary: check and repair a Linux filesystem

text:
# fsck(8)

## NAME
fsck - check and repair a Linux filesystem

## SYNOPSIS
fsck [-lsAVRTMNP] [-r [fd]] [-C [fd]] [-t fstype] [filesystem...] [--] [fs-specific-options]

## DESCRIPTION
fsck is used to check and optionally repair one or more Linux filesystems. filesystem can be a device name (e.g., /dev/hdc1, /dev/sdb2), a mount point (e.g., /, /usr, /home), or a filesystem label or UUID specifier (e.g., UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root). Normally, the fsck program will try to handle filesystems on different physical disk drives in parallel to reduce the total amount of time needed to check all of them.

If no filesystems are specified on the command line, and the -A option is not specified, fsck will default to checking filesystems in /etc/fstab serially. This is equivalent to the -As options.

The exit status returned by fsck is the sum of the following conditions:

0

No errors

1

Filesystem errors corrected

2

System should be rebooted

4

Filesystem errors left uncorrected

8

Operational error

16

Usage or syntax error

32

Checking canceled by user request

128

Shared-library error

The exit status returned when multiple filesystems are checked is the bit-wise OR of the exit statuses for each filesystem that is checked.

In actuality, fsck is simply a front-end for the various filesystem checkers (fsck.fstype) available under Linux. The filesystem-specific checker is searched for in the PATH environment variable. If the PATH is undefined then fallback to /sbin.

Please see the filesystem-specific checker manual pages for further details.

## OPTIONS
-l

Create an exclusive flock(2) lock file (/run/fsck/<diskname>.lock) for whole-disk device. This option can be used with one device only (this means that -A and -l are mutually exclusive). This option is recommended when more fsck instances are executed in the same time. The option is ignored when used for multiple devices or for non-rotating disks. fsck does not lock underlying devices when executed to check stacked devices (e.g. MD or DM) - this feature is not implemented yet.

-r [fd]

Report certain statistics for each fsck when it completes. These statistics include the exit status, the maximum run set size (in kilobytes), the elapsed all-clock time and the user and system CPU time used by the fsck run. For example: /dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592, sys 0.86186

GUI front-ends may specify a file descriptor fd, in which case the progress bar information will be sent to that file descriptor in a machine parsable format. For example:

/dev/sda1 0 92828 4.002804 2.677592 0.86186

-s

Serialize fsck operations. This is a good idea if you are checking multiple filesystems and the checkers are in an interactive mode. (Note: e2fsck(8) runs in an interactive mode by default. To make e2fsck(8) run in a non-interactive mode, you must either specify the -p or -a option, if you wish for errors to be corrected automatically, or the -n option if you do not.)

-t fslist

Specifies the type(s) of filesystem to be checked. When the -A flag is specified, only filesystems that match fslist are checked. The fslist parameter is a comma-separated list of filesystems and options specifiers. All of the filesystems in this comma-separated list may be prefixed by a negation operator 'no' or '!', which requests that only those filesystems not listed in fslist will be checked. If none of the filesystems in fslist is prefixed by a negation operator, then only those listed filesystems will be checked. Options specifiers may be included in the comma-separated fslist. They must have the format opts=fs-option. If an options specifier is present, then only filesystems which contain fs-option in their mount options field of /etc/fstab will be checked. If the options specifier is prefixed by a negation operator, then only those filesystems that do not have fs-option in their mount options field of /etc/fstab will be checked.

For example, if opts=ro appears in fslist, then only filesystems listed in /etc/fstab with the ro option will be checked.

For compatibility with Mandrake distributions whose boot scripts depend upon an unauthorized UI change to the fsck program, if a filesystem type of loop is found in fslist, it is treated as if opts=loop were specified as an argument to the -t option.

Normally, the filesystem type is deduced by searching for filesys in the /etc/fstab file and using the corresponding entry. If the type cannot be deduced, and there is only a single filesystem given as an argument to the -t option, fsck will use the specified filesystem type. If this type is not available, then the default filesystem type (currently ext2) is used.

-A

Walk through the /etc/fstab file and try to check all filesystems in one run. This option is typically used from the /etc/rc system initialization file, instead of multiple commands for checking a single filesystem. The root filesystem will be checked first unless the -P option is specified (see below). After that, filesystems will be checked in the order specified by the fs_passno (the sixth) field in the /etc/fstab file. Filesystems with a fs_passno value of 0 are skipped and are not checked at all. Filesystems with a fs_passno value of greater than zero will be checked in order, with filesystems with the lowest fs_passno number being checked first. If there are multiple filesystems with the same pass number, fsck will attempt to check them in parallel, although it will avoid running multiple filesystem checks on the same physical disk.

fsck does not check stacked devices (RAIDs, dm-crypt, ...) in parallel with any other device. See below for FSCK_FORCE_ALL_PARALLEL setting. The /sys filesystem is used to determine dependencies between devices.

Hence, a very common configuration in /etc/fstab files is to set the root filesystem to have a fs_passno value of 1 and to set all other filesystems to have a fs_passno value of 2. This will allow fsck to automatically run filesystem checkers in parallel if it is advantageous to do so. System administrators might choose not to use this configuration if they need to avoid multiple filesystem checks running in parallel for some reason - for example, if the machine in question is short on memory so that excessive paging is a concern.

fsck normally does not check whether the device actually exists before calling a filesystem specific checker. Therefore non-existing devices may cause the system to enter filesystem repair mode during boot if the filesystem specific checker returns a fatal error. The /etc/fstab mount option nofail may be used to have fsck skip non-existing devices. fsck also skips non-existing devices that have the special filesystem type auto.

-C [fd]

Display completion/progress bars for those filesystem checkers (currently only for ext[234]) which support them. fsck will manage the filesystem checkers so that only one of them will display a progress bar at a time. GUI front-ends may specify a file descriptor fd, in which case the progress bar information will be sent to that file descriptor.

-M

Do not check mounted filesystems and return an exit status of 0 for mounted filesystems.

-N

Don’t execute, just show what would be done.

-P

When the -A flag is set, check the root filesystem in parallel with the other filesystems. This is not the safest thing in the world to do, since if the root filesystem is in doubt things like the e2fsck(8) executable might be corrupted! This option is mainly provided for those sysadmins who don’t want to repartition the root filesystem to be small and compact (which is really the right solution).

-R

When checking all filesystems with the -A flag, skip the root filesystem. (This is useful in case the root filesystem has already been mounted read-write.)

-T

Don’t show the title on startup.

-V

Produce verbose output, including all filesystem-specific commands that are executed.

-?, --help

Display help text and exit.

--version

Display version information and exit.

## FILESYSTEM SPECIFIC OPTIONS
Options which are not understood by fsck are passed to the filesystem-specific checker!

These options must not take arguments, as there is no way for fsck to be able to properly guess which options take arguments and which don’t.

Options and arguments which follow the -- are treated as filesystem-specific options to be passed to the filesystem-specific checker.

Please note that fsck is not designed to pass arbitrarily complicated options to filesystem-specific checkers. If you’re doing something complicated, please just execute the filesystem-specific checker directly. If you pass fsck some horribly complicated options and arguments, and it doesn’t do what you expect, don’t bother reporting it as a bug. You’re almost certainly doing something that you shouldn’t be doing with fsck. Options to different filesystem-specific fsck’s are not standardized.

## ENVIRONMENT
The fsck program’s behavior is affected by the following environment variables:

FSCK_FORCE_ALL_PARALLEL

If this environment variable is set, fsck will attempt to check all of the specified filesystems in parallel, regardless of whether the filesystems appear to be on the same device. (This is useful for RAID systems or high-end storage systems such as those sold by companies such as IBM or EMC.) Note that the fs_passno value is still used.

FSCK_MAX_INST

This environment variable will limit the maximum number of filesystem checkers that can be running at one time. This allows configurations which have a large number of disks to avoid fsck starting too many filesystem checkers at once, which might overload CPU and memory resources available on the system. If this value is zero, then an unlimited number of processes can be spawned. This is currently the default, but future versions of fsck may attempt to automatically determine how many filesystem checks can be run based on gathering accounting data from the operating system.

PATH

The PATH environment variable is used to find filesystem checkers.

FSTAB_FILE

This environment variable allows the system administrator to override the standard location of the /etc/fstab file. It is also useful for developers who are testing fsck.

LIBBLKID_DEBUG=all

enables libblkid debug output.

LIBMOUNT_DEBUG=all

enables libmount debug output.

## FILES
/etc/fstab

## AUTHORS
Theodore Ts’o <tytso@mit.edu>>, Karel Zak <kzak@redhat.com>

## SEE ALSO
fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8), fsck.cramfs(8), fsck.jfs(8), fsck.nfs(8), fsck.minix(8), fsck.msdos(8), fsck.vfat(8), fsck.xfs(8), reiserfsck(8)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The fsck command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


fsck.cramfs

title: fsck.cramfs(8)

summary: fsck compressed ROM file system

text:
# fsck.cramfs(8)

## NAME
fsck.cramfs - fsck compressed ROM file system

## SYNOPSIS
fsck.cramfs [options] file

## DESCRIPTION
fsck.cramfs is used to check the cramfs file system.

## OPTIONS
-v, --verbose

Enable verbose messaging.

-b, --blocksize blocksize

Use this blocksize, defaults to page size. Must be equal to what was set at creation time. Only used for --extract.

--extract[=directory]

Test to uncompress the whole file system. Optionally extract contents of the file to directory.

-a

This option is silently ignored.

-y

This option is silently ignored.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## EXIT STATUS
0

success

4

file system was left uncorrected

8

operation error, such as unable to allocate memory

16

usage information was printed

## SEE ALSO
mount(8), mkfs.cramfs(8)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The fsck.cramfs command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.


fsfreeze

title: fsfreeze(8)

text:
# fsfreeze(8)

## NAME
fsfreeze - suspend access to a filesystem (Ext3/4, ReiserFS, JFS, XFS)

## SYNOPSIS
fsfreeze --freeze|--unfreeze mountpoint

## DESCRIPTION
fsfreeze suspends or resumes access to a filesystem.

fsfreeze halts any new access to the filesystem and creates a stable image on disk. fsfreeze is intended to be used with hardware RAID devices that support the creation of snapshots.

fsfreeze is unnecessary for device-mapper devices. The device-mapper (and LVM) automatically freezes a filesystem on the device when a snapshot creation is requested. For more details see the dmsetup(8) man page.

The mountpoint argument is the pathname of the directory where the filesystem is mounted. The filesystem must be mounted to be frozen (see mount(8)).

Note that access-time updates are also suspended if the filesystem is mounted with the traditional atime behavior (mount option strictatime, for more details see mount(8)).

## OPTIONS
-f, --freeze

This option requests the specified filesystem to be frozen from new modifications. When this is selected, all ongoing transactions in the filesystem are allowed to complete, new write(2) system calls are halted, other calls which modify the filesystem are halted, and all dirty data, metadata, and log information are written to disk. Any process attempting to write to the frozen filesystem will block waiting for the filesystem to be unfrozen. Note that even after freezing, the on-disk filesystem can contain information on files that are still in the process of unlinking. These files will not be unlinked until the filesystem is unfrozen or a clean mount of the snapshot is complete.

-u, --unfreeze

This option is used to un-freeze the filesystem and allow operations to continue. Any filesystem modifications that were blocked by the freeze are unblocked and allowed to complete.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

## FILESYSTEM SUPPORT
This command will work only if filesystem supports has support for freezing. List of these filesystems include (2016-12-18) btrfs, ext2/3/4, f2fs, jfs, nilfs2, reiserfs, and xfs. Previous list may be incomplete, as more filesystems get support. If in doubt easiest way to know if a filesystem has support is create a small loopback mount and test freezing it.

## NOTES
This man page is based on xfs_freeze(8).

## AUTHORS
Written by Hajime Taira.

## SEE ALSO
mount(8)

## REPORTING BUGS
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.

## AVAILABILITY
The fsfreeze command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.