syslog.conf

package: syslogd

title: syslog.conf(5)

summary: syslogd(8) configuration file

text:
# syslog.conf(5)

## NAME
syslog.conf - syslogd(8) configuration file

## DESCRIPTION
The syslog.conf file is the main configuration file for syslogd(8) which logs system messages on *nix systems. This file specifies rules for logging. For special features see the sysklogd(8) manpage.

Every rule consists of two fields, a selector field and an action field. These two fields are separated by one or more spaces or tabs. The selector field specifies a pattern of facilities and priorities belonging to the specified action.

Lines starting with a hash mark (``#'') and empty lines are ignored.

This variant of syslogd is able to understand a slightly extended syntax compared to the original BSD syslogd. One rule may be divided into several lines if the leading line is terminated with an backslash (``\'').

### Directives
The log_format is a directive to define the format of the logged messages. By default, the message format is:

```
log_format: %t %h %m
```

### Format of the format string
The format string is a character string. The format string is composed of zero or more directives: ordinary characters (not %), which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching the entire message or parts of it. Each conversion specification is introduced by the character %, and ends with a specifier.

### Specifiers
The specifiers and their meanings are:

\\

backslash character.

\b

backspace character,

\f

form feed character.

\n

new line character.

\r

carriage return character.

\t

horizontal tab character.

%%

a single ``%'' character.

%t

time of last occurrence.

%h

host from which this message.

%T

message tag if any.

%C

message content.

%m

message text. According to section 4.1.3 of RFC 3164, a message has two fields known as the TAG field and the CONTENT field. The value in the TAG field will be the name of the program or process that generated the message. The CONTENT contains the details of the message. Ths ``%m'' specifier is just a combination of two other specifiers: ``%T: %C''.

%u

user who sent the message.

%g

user group who sent the message.

%p

PID of the process that sent the message.

%H

hash of current message + hash of previous message. This hash is the address of this message and all others until the server starts. Each time the server starts, it starts creating a checksum chain for each log file. On restart, the chain starts with an empty checksum.

The %u, %g, and %p specifiers are only meaningful if the message was received via a UNIX domain socket. In all other cases, their values will be zero.

## SELECTORS
The selector field consists of two parts, a facility and a priority, separated by a period (``.''). Both parts are case insensitive and can also be specified as decimal numbers corresponding to the definitions in /usr/include/syslog.h. It is safer to use symbolic names rather than decimal numbers. Both facilities and priorities are described in syslog(3). The names mentioned below correspond to the similar LOG_-values in /usr/include/syslog.h.

The facility is one of the following keywords: auth, authpriv, cron, daemon, ftp, kern, lpr, mail, mark, news, security (same as auth), syslog, user, uucp and local0 through local7. The keyword security is deprecated and mark is only for internal use and therefore should not be used in applications. The facility specifies the subsystem that produced the message, e.g. all mail programs log with the mail facility (LOG_MAIL) if they log using syslog.

In most cases anyone can log to any facility, so we rely on convention for the correct facility to be chosen. However, generally only the kernel can log to the "kern" facility. This is because the implementation of openlog() and syslog() in glibc does not allow logging to the "kern" facility. Klogd circumvents this restriction when logging to syslogd by reimplementing those functions itself.

The priority is one of the following keywords, in ascending order: debug, info, notice, warning, warn (same as warning), err, error (same as err), crit, alert, emerg, panic (same as emerg). The keywords warn, error and panic are deprecated and should not be used anymore. The priority defines the severity of the message

The behavior of the original BSD syslogd is that all messages of the specified priority and higher are logged according to the given action. This syslogd(8) behaves the same, but has some extensions.

In addition to the above mentioned names the syslogd(8) understands the following extensions: An asterisk (``*'') stands for all facilities or all priorities, depending on where it is used (before or after the period). The keyword none stands for no priority of the given facility.

Multiple facilities may be specified for a single priority pattern in one statement using the comma (``,'') operator to separate the facilities. You may specify as many facilities as you want. Please note that only the facility part from such a statement is taken, a priority part would be ignored.

Multiple selectors may be specified for a single action using the semicolon (``;'') separator. Selectors are processed from left to right, with each selector being able to overwrite preceding ones. Using this behavior you are able to exclude some priorities from the pattern.

This syslogd(8) has a syntax extension to the original BSD source, which makes its use more intuitive. You may precede every priority with an equation sign (``='') to specify that syslogd should only refer to this single priority and not this priority and all higher priorities.

You may also precide the priority with an exclamation mark (``!'') if you want syslogd to ignore this priority and all higher priorities. You may even use both, the exclamation mark and the equation sign if you want syslogd to ignore only this single priority. If you use both extensions than the exclamation mark must occur before the equation sign, just use it intuitively.

## ACTIONS
The action field of a rule describes the abstract term ``logfile''. A ``logfile'' need not to be a real file, btw. The syslogd(8) provides the following actions.

### Regular File
Typically messages are logged to real files. The filename is specified with an absolute pathname.

You may prefix each entry with a minus sign (``-'') to avoid syncing the file after each log message. Note that you might lose information if the system crashes right after a write attempt. Nevertheless this might give you back some performance, especially if you run programs that use logging in a very verbose manner.

### Named Pipes
This version of syslogd(8) has support for logging output to named pipes (fifos). A fifo or named pipe can be used as a destination for log messages by prepending a pipe symbol (``|'') to the name of the file. This is handy for debugging. Note that the fifo must be created with the mkfifo(1) command before syslogd(8) is started.

### Terminal and Console
If the file you specified is a tty, special tty-handling is done, same with /dev/console.

### Remote Machine
This syslogd(8) provides full remote logging, i.e. is able to send messages to a remote host running syslogd(8) and to receive messages from remote hosts. The remote host won't forward the message again, it will just log them locally. To forward messages to another host, prepend the hostname with the at sign (``@'').

Using this feature you are able to collect all syslog messages on a central host, if all other machines log remotely to that one. This reduces administration needs.

Using a named pipe log method, messages from remote hosts can be sent to a log program. By reading log messages line by line such a program is able to sort log messages by host name or program name on the central log host. This way it is possible to split the log into separate files.

### UNIX domain socket
In addition to Remote Machine this syslogd(8) has the ability to forward messages to a UNIX domain socket. To use UNIX domain socket, you need to specify the path to the socket after the at sign (``@''). The path must start with a slash (``/'').

### List of Users
Usually critical messages are also directed to ``root'' on that machine. You can specify a list of users that ought to receive the log message on the terminal by writing their usernames. You may specify more than one user by separating the usernames with commas (``,''). If they're logged in they will receive the log messages.

### Everyone logged on
Emergency messages often go to all users currently online to notify them that something strange is happening with the system. To specify this wall(1)-feature use an asterisk (``*'').

## EXAMPLES
Here are some examples, partially taken from a real existing site and configuration. Hopefully they answer all questions about configuring this syslogd(8). If not, don't hesitate to contact the mailing list.

```
# Store critical stuff in critical
#
*.=crit;kern.none            /var/adm/critical
```

This will store all messages of priority crit in the file /var/adm/critical, with the exception of any kernel messages.

```
# Kernel messages are stored in the kernel file,
# critical messages and higher ones also go
# to another host and to the console
#
kern.*                       /var/adm/kernel
kern.crit                    @finlandia
kern.crit                    /dev/console
kern.info;kern.!err          /var/adm/kernel-info
```

The first rule directs any message that has the kernel facility to the file /var/adm/kernel. (But recall that only the kernel itself can log to this facility.)

The second statement directs all kernel messages of priority crit and higher to the remote host finlandia. This is useful, because if the host crashes and the disks get irreparable errors you might not be able to read the stored messages. If they're on a remote host, too, you still can try to find out the reason for the crash.

The third rule directs kernel messages of priority crit and higher to the actual console, so the person who works on the machine will get them, too.

The fourth line tells the syslogd to save all kernel messages that come with priorities from info up to warning in the file /var/adm/kernel-info.

This is an example of the 2nd selector overwriting part of the first one. The first selector selects kernel messages of priority info and higher. The second selector filters out kernel messages of priority error and higher. This leaves just priorities info, notice and warning to get logged.

```
# The tcp wrapper logs with mail.info, we display
# all the connections on tty12
#
mail.=info                   /dev/tty12
```

This directs all messages that use mail.info (in source LOG_MAIL | LOG_INFO) to /dev/tty12, the 12th console. For example the tcpwrapper tcpd(8) uses this as its default.

```
# Write all mail related logs to a file
#
mail.*;mail.!=info           /var/adm/mail
```

This pattern matches all messages that come with the mail facility, except for the info priority. These will be stored in the file /var/adm/mail.

```
# Log all mail.info and news.info messages to info
#
mail,news.=info              /var/adm/info
```

This will extract all messages that come either with mail.info or with news.info and store them in the file /var/adm/info.

```
# Log info and notice messages to messages file
#
*.=info;*.=notice;\
	mail.none  /var/log/messages
```

This lets the syslogd log all messages that come with either the info or the notice priority into the file /var/log/messages, except for all messages that use the mail facility.

```
# Log info messages to messages file
#
*.=info;\
	mail,news.none       /var/log/messages
```

This statement causes the syslogd to log all messages that come with the info priority to the file /var/log/messages. But any message coming either with the mail or the news facility will not be stored.

```
# Emergency messages will be displayed using wall
#
*.=emerg                     *
```

This rule tells the syslogd to write all emergency messages to all currently logged in users. This is the wall action.

```
# Messages of the priority alert will be directed
# to the operator
#
*.alert                      root,joey
```

This rule directs all messages of priority alert or higher to the terminals of the operator, i.e. of the users ``root'' and ``joey'' if they're logged in.

```
*.*                          @finlandia
```

This rule would redirect all messages to a remote host called finlandia. This is useful especially in a cluster of machines where all syslog messages will be stored on only one machine.

## CONFIGURATION FILE SYNTAX DIFFERENCES
Syslogd uses a slightly different syntax for its configuration file than the original BSD sources. Originally all messages of a specific priority and above were forwarded to the log file. The modifiers ``='', ``!'' and ``-'' were added to make the syslogd more flexible and to use it in a more intuitive manner.

The original BSD syslogd doesn't understand spaces as separators between the selector and the action field.

## FILES
/etc/syslog.conf

Configuration file for syslogd

## BUGS
The effects of multiple selectors are sometimes not intuitive. For example ``mail.crit,*.err'' will select ``mail'' facility messages at the level of ``err'' or higher, not at the level of ``crit'' or higher.

Also, if you specify a selector with an exclamation mark in it which isn't preceded by a corresponding selector without an exclamation mark, nothing will be logged. Intuitively, the selector ``ftp.!alert'' on its own will select all ftp messages with priorities less than alert. In fact it selects nothing. Similarly ``ftp.!=alert'' might reasonably be expected to select all ftp messages other than those with priority alert, but again it selects nothing. It seems the selectors with exclamation marks in them should only be used as `filters' following selectors without exclamation marks.

Finally, using a backslash to divide a line into two doesn't work if the backslash is used immediately after the end of the selector, without intermediate whitespace.

## SEE ALSO
sysklogd(8), klogd(8), logger(1), syslog(2), syslog(3).

## AUTHORS
The syslogd is taken from BSD sources, Greg Wettstein <greg@wind.enjellic.com> performed the port to Linux, Martin Schulze <joey@infodrom.org> fixed some bugs, added several new features and took over maintenance.


sysstat

package: sysstat

title: sysstat(5)

summary: sysstat configuration file.

text:
# sysstat(5)

## NAME
sysstat - sysstat configuration file.

## DESCRIPTION
This file is read by sa1(8) and sa2(8) shell scripts from the sysstat's set of tools. It consists of a sequence of shell variable assignments used to configure sysstat logging. The variables and their meanings are:

COMPRESSAFTER

Number of days after which daily data files are to be compressed. The compression program is given in the ZIP variable.

DELAY_RANGE

Tell sa2 script to wait for a random delay in the indicated range before running. This delay is expressed in seconds, and is aimed at preventing a massive I/O burst at the same time on VM sharing the same storage area. A value of 0 means that sa2 script will generate its reports files immediately.

HISTORY

The number of days during which a daily data file or a report should be kept. Data files or reports older than this number of days will be removed by the sa2(8) shell script. Data files and reports are normally saved in the /var/log/sa directory, under the name saDD (for data files) or sarDD (for reports), where the DD parameter indicates the current day. The number of files actually kept in the /var/log/sa directory may be slightly higher than the HISTORY value due to the way the sa2 script figures out which files are to be removed (see below "How the sa2(8) script applies HISTORY value"). Using a value of 28 keeps a whole month's worth of data. If you set HISTORY to a value greater than 28 then you should consider using sadc's option -D to prevent older data files from being overwritten (see sadc(8) manual page). In this latter case data files are named saYYYYMMDD and reports sarYYYYMMDD, where YYYY stands for the current year, MM for the current month and DD for the current day.

How the sa2(8) script applies HISTORY value

The sa2 script uses the find command with the -mtime option to figure out which files are to be removed. The find command interprets this value as "N 24 hour periods", ignoring any fractional part. This means that the last modified time of a given sa[r]DD data or report file, using a HISTORY of 1, has to have been modified at least two days ago before it will be removed. And for a HISTORY of 28 that would mean 29 days ago.

To figure out how a HISTORY of 28 is applied in practice, we need to consider that the sa2 script that issues the find command to remove the old files typically runs just before midnight on a given system, and since the first record from sadc can also be written to the previous day's data file (thereby moving its modification time up a bit), the sa2 script will leave 30 files untouched. So for a setting of 28, and counting the data file of the current day, there will always be 31 files (or 30 files, depending on the number of days in a month) in the /var/log/sa directory during the majority of a given day. E.g.:

April 30th: 31 files (Apr 30th-1st, Mar 31th)

May 1st: 30 files (May 1st, Apr 30th-2nd)

Yet we can note the following exceptions (as inspected at Noon of the given day):

February 28th: 31 files (Feb 28th-1st, Jan 31st, 30th & 29th)

March 1st: 30 files (Mar 1st, Feb 28th-2nd, Jan 31st & 30th)

March 2nd: 29 files (Mar 1st & 2nd, Feb 28th-3rd, Jan. 31st)

March 3rd: 28 files (Mar 1st-3rd, Feb 28th-4th)

March 4th - March 28th: 28 files

March 29th: 29 files

March 30th: 30 files

March 31st: 31 files

(Determining the number of files in March on a leap year is left as an exercise for the reader).

Things are simpler if you use the sa[r]YYYYMMDD name format. Apply the same logic as above in this case and you will find that there are always HISTORY + 3 files in the /var/log/sa directory during the majority of a given day.

REPEAT_HEADER

Maximum number of lines after which a header will be inserted in the report generated by sa2 script. By default there is only a header at the beginning of each report and it is not repeated afterwards.

REPORTS

Set this variable to false to prevent the sa2 script from generating reports (the sarDD files).

SA_DIR

Directory where the standard system activity daily data and report files are saved. Its default value is /var/log/sa.

SADC_OPTIONS

Options that should be passed to sadc(8). With these options (see sadc(8) manual page), you can select some additional data which are going to be saved in daily data files. These options are used only when a new data file is created. They will be ignored with an already existing one.

UMASK

The sa1 and sa2 scripts generate system activity data and report files in the /var/log/sa directory. By default the files are created with umask 0022 and are therefore readable for all users. Change this variable to restrict the permissions on the files (e.g. use 0027 to adhere to more strict security standards).

YESTERDAY

By default sa2 script generates yesterday's summary, since the cron job usually runs right after midnight. If you want sa2 to generate the summary of the same day (for example when cron job runs at 23:53) set this variable to no.

ZIP

Program used to compress data and report files.

## FILE
/etc/sysconfig/sysstat

## AUTHOR
Sebastien Godard (sysstat <at> orange.fr)

## SEE ALSO
sadc(8), sa1(8), sa2(8)

https://github.com/sysstat/sysstat

https://sysstat.github.io/


binfmt.d

package: systemd

title: binfmt.d(5)

text:
# binfmt.d(5)

## NAME
binfmt.d - Configure additional binary formats for executables at boot

## SYNOPSIS
/etc/binfmt.d/*.conf

/run/binfmt.d/*.conf

/usr/local/lib/binfmt.d/*.conf

/usr/lib/binfmt.d/*.conf

## DESCRIPTION
At boot, systemd-binfmt.service(8) reads configuration files from the above directories to register in the kernel additional binary formats for executables.

## CONFIGURATION FORMAT
Each file contains a list of binfmt_misc kernel binary format rules. Consult the kernel's Kernel Support for miscellaneous Binary Formats (binfmt_misc)[1] documentation file for more information on registration of additional binary formats and how to write rules.

Empty lines and lines beginning with ";" and "#" are ignored. Note that this means you may not use those symbols as the delimiter in binary format rules.

## CONFIGURATION DIRECTORIES AND PRECEDENCE
Configuration files are read from directories in /etc/, /run/, /usr/local/lib/, and /usr/lib/, in order of precedence, as listed in the SYNOPSIS section above. Files must have the ".conf" extension. Files in /etc/ override files with the same name in /run/, /usr/local/lib/, and /usr/lib/. Files in /run/ override files with the same name under /usr/.

All configuration files are sorted by their filename in lexicographic order, regardless of which of the directories they reside in. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Thus, the configuration in a certain file may either be replaced completely (by placing a file with the same name in a directory with higher priority), or individual settings might be changed (by specifying additional settings in a file with a different name that is ordered later).

Packages should install their configuration files in /usr/lib/ (distribution packages) or /usr/local/lib/ (local installs) [2]. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages.

It is recommended to prefix all filenames with a two-digit number and a dash to simplify the ordering. It is recommended to use the range 10-40 for configuration files in /usr/ and the range 60-90 for configuration files in /etc/ and /run/, to make sure that local and transient configuration files will always take priority over configuration files shipped by the OS vendor.

If the administrator wants to disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in the configuration directory in /etc/, with the same filename as the vendor configuration file. If the vendor configuration file is included in the initrd image, the image has to be regenerated.

## EXAMPLE
Example 1. /etc/binfmt.d/wine.conf example:

```
# Start WINE on Windows executables
:DOSWin:M::MZ::/usr/bin/wine:
```

## SEE ALSO
systemd(1), systemd-binfmt.service(8), systemd-delta(1), wine(8)

## NOTES
1.

Kernel Support for miscellaneous Binary Formats (binfmt_misc)

https://docs.kernel.org/admin-guide/binfmt-misc.html

2.

💣💥🧨💥💥💣 Please note that those configuration files must be available at all times. If /usr/local/ is a separate partition, it may not be available during early boot, and must not be used for configuration.


capsule@.service

title: capsule@.service(5)

text:
# capsule@.service(5)

## NAME
capsule@.service - System unit for the capsule service manager

## SYNOPSIS
capsule@NAME.service

## DESCRIPTION
Service managers for capsules run in capsule@NAME.service system units, with the capsule name as the instance identifier. Capsules are way to run additional instances of the service manager, under dynamic user IDs, i.e. UIDs that are allocated when the capsule service manager is started, and released when it is stopped.

In many ways capsule@.service is similar to the per-user user@.service service manager, but there are a few important distinctions:

•The capsule service manager utilizes DynamicUser= (see systemd.exec(5)) to allocate a new UID dynamically on invocation. The user name is automatically generated from the capsule name, by prefixing "c-". The UID is released when the service is terminated. The user service manager on the other hand operates under a statically allocated user ID that must be pre-existing, before the user service manager is invoked.

•User service managers register themselves with pam(8), capsule service managers do not.

•User service managers typically read their configuration from a $HOME directory below /home/, capsule service managers from a $HOME directory below /var/lib/capsules/.

•User service managers are collectively contained in the user.slice unit, capsule service managers in capsule.slice. Also see systemd.special(7).

•User service managers start the user unit default.target initially. Capsule service managers invoke the user unit capsule@.target instead.

The capsule service manager and the capsule's bus broker can be reached via the --capsule= switch to systemctl(1), systemd-run(1) and busctl(1).

New capsules can be started via a simple systemctl start capsule@NAME.service command, and stopped via systemctl stop capsule@NAME.service. Starting a capsule will implicitly create a home directory /var/lib/capsules/NAME/, if missing. A runtime directory is created as /run/capsules/NAME/. To remove these resources use systemctl clean capsule@NAME.service, for example with the --what=all switch.

The capsule@.service unit invokes a systemd --user service manager process. This means unit files are looked for according to the sames rules as for regular user service managers, for example in /var/lib/capsules/NAME/.config/systemd/user/.

Capsule names may be chosen freely by the user, however, they must be suitable as UNIX filenames (i.e. 255 characters max, and contain no "/"), and when prefixed with "p-" be suitable as a user name matching strict POSIX rules, see User/Group Name Syntax[1] for details.

Added in version 256.

## EXAMPLES
Example 1. Create a new capsule, invoke two programs in it (one interactively), terminate it, and clean everything up

```
# systemctl start capsule@tatze.service
# systemd-run --capsule=tatze --unit=sleeptest.service sleep 999
# systemctl --capsule=tatze status sleeptest.service
# systemd-run -t --capsule=tatze bash
# systemctl --capsule=tatze stop sleeptest.service
# systemctl stop capsule@tatze.service
# systemctl clean --all capsule@tatze.service
```

## SEE ALSO
systemd(1), user@.service(5), systemd.service(5), systemd.slice(5), systemd.exec(5), systemd.special(7), systemctl(1), systemd-run(1), busctl(1), pam(8)

## NOTES
1.

User/Group Name Syntax

https://systemd.io/USER_NAMES


crypttab

title: crypttab(5)

text:
# crypttab(5)

## NAME
crypttab - Configuration for encrypted block devices

## SYNOPSIS
/etc/crypttab

## DESCRIPTION
The /etc/crypttab file describes encrypted block devices that are set up during system boot.

Empty lines and lines starting with the "#" character are ignored. Each of the remaining lines describes one encrypted block device. Fields are delimited by white space.

Each line is in the form

```
volume-name encrypted-device key-file options
```

The first two fields are mandatory, the remaining two are optional.

Setting up encrypted block devices using this file supports four encryption modes: LUKS, TrueCrypt, BitLocker and plain. See cryptsetup(8) for more information about each mode. When no mode is specified in the options field and the block device contains a LUKS signature, it is opened as a LUKS device; otherwise, it is assumed to be in raw dm-crypt (plain mode) format.

The four fields of /etc/crypttab are defined as follows:

1.The first field contains the name of the resulting volume with decrypted data; its block device is set up below /dev/mapper/.

2.The second field contains a path to the underlying block device or file, or a specification of a block device via "UUID=" followed by the UUID.

3.The third field specifies an absolute path to a file with the encryption key. Optionally, the path may be followed by ":" and an /etc/fstab style device specification (e.g. starting with "LABEL=" or similar); in which case the path is taken relative to the specified device's file system root. If the field is not present or is "none" or "-", a key file named after the volume to unlock (i.e. the first column of the line), suffixed with .key is automatically loaded from the /etc/cryptsetup-keys.d/ and /run/cryptsetup-keys.d/ directories, if present. Otherwise, the password has to be manually entered during system boot. For swap encryption, /dev/urandom may be used as key file, resulting in a randomized key. If the specified key file path refers to an AF_UNIX stream socket in the file system, the key is acquired by connecting to the socket and reading it from the connection. This allows the implementation of a service to provide key information dynamically, at the moment when it is needed. For details see below.

4.The fourth field, if present, is a comma-delimited list of options. The supported options are listed below.

## KEY ACQUISITION
Six different mechanisms for acquiring the decryption key or passphrase unlocking the encrypted volume are supported. Specifically:

1.Most prominently, the user may be queried interactively during volume activation (i.e. typically at boot), asking them to type in the necessary passphrases.

2.The (unencrypted) key may be read from a file on disk, possibly on removable media. The third field of each line encodes the location, for details see above.

3.The (unencrypted) key may be requested from another service, by specifying an AF_UNIX file system socket in place of a key file in the third field. For details see above and below.

4.The key may be acquired via a PKCS#11 compatible hardware security token or smartcard. In this case, a saved key used in unlock process is stored on disk/removable media, acquired via AF_UNIX, or stored in the LUKS2 JSON token metadata header. For RSA, the saved key is an encrypted volume key. The encrypted volume key is then decrypted by the PKCS#11 token with an RSA private key stored on it, and used to unlock the encrypted volume. For elliptic-curve (EC) cryptography, the saved key is the public key generated in enrollment process. The public key is then used to derive a shared secret with a private key stored in the PKCS#11 token. The derived shared secret is then used to unlock the volume. Use the pkcs11-uri= option described below to use this mechanism.

5.Similarly, the key may be acquired via a FIDO2 compatible hardware security token (which must implement the "hmac-secret" extension). In this case, a key generated randomly during enrollment is stored on disk/removable media, acquired via AF_UNIX, or stored in the LUKS2 JSON token metadata header. The random key is hashed via a keyed hash function (HMAC) on the FIDO2 token, using a secret key stored on the token that never leaves it. The resulting hash value is then used as key to unlock the encrypted volume. Use the fido2-device= option described below to use this mechanism.

6.Similarly, the key may be acquired via a TPM2 security chip. In this case, a (during enrollment) randomly generated key — encrypted by an asymmetric key derived from the TPM2 chip's seed key — is stored on disk/removable media, acquired via AF_UNIX, or stored in the LUKS2 JSON token metadata header. Use the tpm2-device= option described below to use this mechanism.

For the latter five mechanisms the source for the key material used for unlocking the volume is primarily configured in the third field of each /etc/crypttab line, but may also be configured in /etc/cryptsetup-keys.d/ and /run/cryptsetup-keys.d/ (see above) or in the LUKS2 JSON token header (in case of the latter three). Use the systemd-cryptenroll(1) tool to enroll PKCS#11, FIDO2 and TPM2 devices in LUKS2 volumes.

## SUPPORTED OPTIONS
The following options may be used in the fourth field of each line:

cipher=

Specifies the cipher to use. See cryptsetup(8) for possible values and the default value of this option. A cipher with unpredictable IV values, such as "aes-cbc-essiv:sha256", is recommended. Embedded commas in the cipher specification need to be escaped by preceding them with a backslash, see example below. Added in version 186.

discard

Allow discard requests to be passed through the encrypted block device. This improves performance on SSD storage but has security implications. Added in version 207.

hash=

Specifies the hash to use for password hashing. See cryptsetup(8) for possible values and the default value of this option. Added in version 186.

header=

Use a detached (separated) metadata device or file where the header containing the master key(s) is stored. This option is only relevant for LUKS and TrueCrypt/VeraCrypt devices. See cryptsetup(8) for possible values and the default value of this option. Optionally, the path may be followed by ":" and an /etc/fstab device specification (e.g. starting with "UUID=" or similar); in which case, the path is relative to the device file system root. The device gets mounted automatically for LUKS device activation duration only.

Added in version 219.

keyfile-offset=

Specifies the number of bytes to skip at the start of the key file. See cryptsetup(8) for possible values and the default value of this option. Added in version 187.

keyfile-size=

Specifies the maximum number of bytes to read from the key file. See cryptsetup(8) for possible values and the default value of this option. This option is ignored in plain encryption mode, where the key file size is determined by the key size. It is also ignored when the key file is used as a salt file for a FIDO2 token, as the salt size in that case is defined by the FIDO2 specification to be exactly 32 bytes. Added in version 188.

keyfile-erase

If enabled, the specified key file is erased after the volume is activated or when activation fails. This is in particular useful when the key file is only acquired transiently before activation (e.g. via a file in /run/, generated by a service running before activation), and shall be removed after use. Defaults to off. Added in version 246.

key-slot=

Specifies the key slot to compare the passphrase or key against. If the key slot does not match the given passphrase or key, but another would, the setup of the device will fail regardless. This option implies luks. See cryptsetup(8) for possible values. The default is to try all key slots in sequential order. Added in version 209.

keyfile-timeout=

Specifies the timeout for the device on which the key file resides or the device used as the key file, and falls back to a password if it could not be accessed. See systemd-cryptsetup-generator(8) for key files on external devices. Added in version 243.

link-volume-key=

Specifies the kernel keyring and key description (see keyrings(7)) where LUKS2 volume key gets linked during device activation. The kernel keyring description and key description must be separated by "::". The kernel keyring part can be a string description or a predefined kernel keyring prefixed with "@" (e.g.: to use "@s" session or "@u" user keyring directly). The type prefix text in the kernel keyring description is not required. The specified kernel keyring must already exist at the time of device activation.

The key part is a string description optionally prefixed by a "%key_type:". If no type is specified, the "user" type key is linked by default. See keyctl(1) for more information on key descriptions (KEY IDENTIFIERS section).

Note that the linked volume key is not cleaned up automatically when the device is detached.

Added in version 256.

luks

Force LUKS mode. When this mode is used, the following options are ignored since they are provided by the LUKS header on the device: cipher=, hash=, size=. Added in version 186.

bitlk

Decrypt BitLocker drive. Encryption parameters are deduced by cryptsetup from BitLocker header. Added in version 246.

_netdev

Marks this cryptsetup device as requiring network. It will be started after the network is available, similarly to systemd.mount(5) units marked with _netdev. The service unit to set up this device will be ordered between remote-fs-pre.target and remote-cryptsetup.target, instead of cryptsetup-pre.target and cryptsetup.target. Hint: if this device is used for a mount point that is specified in fstab(5), the _netdev option should also be used for the mount point. Otherwise, a dependency loop might be created where the mount point will be pulled in by local-fs.target, while the service to configure the network is usually only started after the local file system has been mounted.

Added in version 235.

noauto

This device will not be added to cryptsetup.target. This means that it will not be automatically unlocked on boot, unless something else pulls it in. In particular, if the device is used for a mount point, it'll be unlocked automatically during boot, unless the mount point itself is also disabled with noauto. Added in version 186.

nofail

This device will not be a hard dependency of cryptsetup.target. It'll still be pulled in and started, but the system will not wait for the device to show up and be unlocked, and boot will not fail if this is unsuccessful. Note that other units that depend on the unlocked device may still fail. In particular, if the device is used for a mount point, the mount point itself also needs to have the nofail option, or the boot will fail if the device is not unlocked successfully. If a keyfile and/or a header are specified, the dependencies on their respective directories will also not be fatal, so that umounting said directories will not cause the generated cryptset unit to be deactivated. Added in version 186.

offset=

Start offset in the backend device, in 512-byte sectors. This option is only relevant for plain devices. Added in version 220.

plain

Force plain encryption mode. Added in version 186.

read-only, readonly

Set up the encrypted block device in read-only mode. Added in version 186.

same-cpu-crypt

Perform encryption using the same CPU that IO was submitted on. The default is to use an unbound workqueue so that encryption work is automatically balanced between available CPUs. This requires kernel 4.0 or newer.

Added in version 242.

submit-from-crypt-cpus

Disable offloading writes to a separate thread after encryption. There are some situations where offloading write requests from the encryption threads to a dedicated thread degrades performance significantly. The default is to offload write requests to a dedicated thread because it benefits the CFQ scheduler to have writes submitted using the same context. This requires kernel 4.0 or newer.

Added in version 242.

no-read-workqueue

Bypass dm-crypt internal workqueue and process read requests synchronously. The default is to queue these requests and process them asynchronously. This requires kernel 5.9 or newer.

Added in version 248.

no-write-workqueue

Bypass dm-crypt internal workqueue and process write requests synchronously. The default is to queue these requests and process them asynchronously. This requires kernel 5.9 or newer.

Added in version 248.

skip=

How many 512-byte sectors of the encrypted data to skip at the beginning. This is different from the offset= option with respect to the sector numbers used in initialization vector (IV) calculation. Using offset= will shift the IV calculation by the same negative amount. Hence, if offset=n is given, sector n will get a sector number of 0 for the IV calculation. Using skip= causes sector n to also be the first sector of the mapped device, but with its number for IV generation being n. This option is only relevant for plain devices.

Added in version 220.

size=

Specifies the key size in bits. See cryptsetup(8) for possible values and the default value of this option. Added in version 186.

sector-size=

Specifies the sector size in bytes. See cryptsetup(8) for possible values and the default value of this option. Added in version 240.

swap

The encrypted block device will be used as a swap device, and will be formatted accordingly after setting up the encrypted block device, with mkswap(8). This option implies plain.

Warning

Using the swap option will destroy the contents of the named partition during every boot, so make sure the underlying block device is specified correctly.

Added in version 186.

tcrypt

Use TrueCrypt encryption mode. When this mode is used, the following options are ignored since they are provided by the TrueCrypt header on the device or do not apply: cipher=, hash=, keyfile-offset=, keyfile-size=, size=. When this mode is used, the passphrase is read from the key file given in the third field. Only the first line of this file is read, excluding the new line character.

Note that the TrueCrypt format uses both passphrase and key files to derive a password for the volume. Therefore, the passphrase and all key files need to be provided. Use tcrypt-keyfile= to provide the absolute path to all key files. When using an empty passphrase in combination with one or more key files, use "/dev/null" as the password file in the third field.

Added in version 206.

tcrypt-hidden

Use the hidden TrueCrypt volume. This option implies tcrypt. This will map the hidden volume that is inside of the volume provided in the second field. Please note that there is no protection for the hidden volume if the outer volume is mounted instead. See cryptsetup(8) for more information on this limitation.

Added in version 206.

tcrypt-keyfile=

Specifies the absolute path to a key file to use for a TrueCrypt volume. This implies tcrypt and can be used more than once to provide several key files. See the entry for tcrypt on the behavior of the passphrase and key files when using TrueCrypt encryption mode.

Added in version 206.

tcrypt-system

Use TrueCrypt in system encryption mode. This option implies tcrypt. Added in version 206.

tcrypt-veracrypt

Check for a VeraCrypt volume. VeraCrypt is a fork of TrueCrypt that is mostly compatible, but uses different, stronger key derivation algorithms that cannot be detected without this flag. Enabling this option could substantially slow down unlocking, because VeraCrypt's key derivation takes much longer than TrueCrypt's. This option implies tcrypt. Added in version 232.

veracrypt-pim=

Specifies a custom Personal Iteration Multiplier (PIM) value, which can range from 0..2147468 for standard veracrypt volumes and 0..65535 for veracrypt system volumes. A value of 0 will imply the VeraCrypt default. This option is only effective when tcrypt-veracrypt is set. Note that VeraCrypt enforces a minimal allowed PIM value depending on the password strength and the hash algorithm used for key derivation, however veracrypt-pim= is not checked against these bounds. See Veracrypt Personal Iterations Multiplier[1] documentation for more information.

Added in version 254.

timeout=

Specifies the timeout for querying for a password. If no unit is specified, seconds is used. Supported units are s, ms, us, min, h, d. A timeout of 0 waits indefinitely (which is the default). Added in version 186.

tmp=

The encrypted block device will be prepared for using it as /tmp/; it will be formatted using mkfs(8). Takes a file system type as argument, such as "ext4", "xfs" or "btrfs". If no argument is specified defaults to "ext4". This option implies plain.

Warning

Using the tmp option will destroy the contents of the named partition during every boot, so make sure the underlying block device is specified correctly.

Added in version 186.

tries=

Specifies the maximum number of times the user is queried for a password. The default is 3. If set to 0, the user is queried for a password indefinitely. Added in version 186.

headless=

Takes a boolean argument, defaults to false. If true, never query interactively for the password/PIN. Useful for headless systems. Added in version 249.

verify

If the encryption password is read from console, it has to be entered twice to prevent typos. Added in version 186.

password-echo=yes|no|masked

Controls whether to echo passwords or security token PINs that are read from console. Takes a boolean or the special string "masked". The default is password-echo=masked. If enabled, the typed characters are echoed literally. If disabled, the typed characters are not echoed in any form, the user will not get feedback on their input. If set to "masked", an asterisk ("*") is echoed for each character typed. Regardless of which mode is chosen, if the user hits the tabulator key ("↹") at any time, or the backspace key ("⌫") before any other data has been entered, then echo is turned off.

Added in version 249.

password-cache=yes|no|read-only

Controls whether to use cache for passwords or security token PINs. Takes a boolean or the special string "read-only". Defaults to "yes". If set to "read-only", the kernel keyring is checked for a password/PIN before requesting one interactively. If set to "yes", in addition to checking the keyring, any password/PIN entered interactively is cached in the keyring with a 2.5-minute timeout before being purged.

Note that this option is not permitted for PKCS#11 security tokens. The reasoning behind this is that PKCS#11 security tokens are usually configured to lock after being supplied an invalid PIN multiple times, so using the cache might inadvertently lock the token.

Added in version 257.

pkcs11-uri=

Takes either the special value "auto" or an RFC7512 PKCS#11 URI[2] pointing to a private key which is used to decrypt the encrypted key specified in the third column of the line. This is useful for unlocking encrypted volumes through PKCS#11 compatible security tokens or smartcards. See below for an example how to set up this mechanism for unlocking a LUKS2 volume with a YubiKey security token. If specified as "auto" the volume must be of type LUKS2 and must carry PKCS#11 security token metadata in its LUKS2 JSON token section. In this mode the URI and the encrypted key are automatically read from the LUKS2 JSON token header. Use systemd-cryptenroll(1) as a simple tool for enrolling PKCS#11 security tokens or smartcards in a way compatible with "auto". In this mode the third column of the line should remain empty (that is, specified as "-").

The specified URI can refer directly to a private key stored on a token or alternatively just to a slot or token, in which case a search for a suitable private key will be performed. In this case, if multiple suitable objects are found, the token is refused. The keyfile configured in the third column of the line is used as is (i.e. in binary form, unprocessed). The resulting decrypted key (for RSA) or derived shared secret (for ECC) is then Base64 encoded before it is used to unlock the LUKS volume.

Use systemd-cryptenroll --pkcs11-token-uri=list to list all suitable PKCS#11 security tokens currently plugged in, along with their URIs.

Note that many newer security tokens that may be used as PKCS#11 security token typically also implement the newer and simpler FIDO2 standard. Consider using fido2-device= (described below) to enroll it via FIDO2 instead. Note that a security token enrolled via PKCS#11 cannot be used to unlock the volume via FIDO2, unless also enrolled via FIDO2, and vice versa.

Added in version 245.

fido2-device=

Takes either the special value "auto" or the path to a "hidraw" device node (e.g. /dev/hidraw1) referring to a FIDO2 security token that implements the "hmac-secret" extension (most current hardware security tokens do). See below for an example how to set up this mechanism for unlocking an encrypted volume with a FIDO2 security token. If specified as "auto" the FIDO2 token device is automatically discovered, as it is plugged in.

FIDO2 volume unlocking requires a client ID hash (CID) to be configured via fido2-cid= (see below) and a key to pass to the security token's HMAC functionality (configured in the line's third column) to operate. If not configured and the volume is of type LUKS2, the CID and the key are read from LUKS2 JSON token metadata instead. Use systemd-cryptenroll(1) as simple tool for enrolling FIDO2 security tokens for LUKS2 volumes.

Use systemd-cryptenroll --fido2-device=list to list all suitable FIDO2 security tokens currently plugged in, along with their device nodes.

This option implements the following mechanism: the configured key is hashed via they HMAC keyed hash function the FIDO2 device implements, keyed by a secret key embedded on the device. The resulting hash value is Base64 encoded and used to unlock the LUKS2 volume. As it should not be possible to extract the secret from the hardware token, it should not be possible to retrieve the hashed key given the configured key — without possessing the hardware token.

Note that many security tokens that implement FIDO2 also implement PKCS#11, suitable for unlocking volumes via the pkcs11-uri= option described above. Typically the newer, simpler FIDO2 standard is preferable.

Added in version 248.

fido2-cid=

Takes a Base64 encoded FIDO2 client ID to use for the FIDO2 unlock operation. If specified, but fido2-device= is not, fido2-device=auto is implied. If fido2-device= is used but fido2-cid= is not, the volume must be of LUKS2 type, and the CID is read from the LUKS2 JSON token header. Use systemd-cryptenroll(1) for enrolling a FIDO2 token in the LUKS2 header compatible with this automatic mode. Added in version 248.

fido2-rp=

Takes a string, configuring the FIDO2 Relying Party (rp) for the FIDO2 unlock operation. If not specified, "io.systemd.cryptsetup" is used, except if the LUKS2 JSON token header contains a different value. It should normally not be necessary to override this. Added in version 248.

fido2-pin=

Controls whether to require the user to enter a PIN when unlocking the volume (the FIDO2 "clientPin" feature). This option only applies when in manual mode, i.e. when fido2-cid= option is set. Defaults to neither true or false, but rather to v248 behavior, that is: try with no PIN first, but if token reports that PIN is required, try again asking for PIN. Added in version 257.

fido2-up=

Controls whether to require the user to verify presence (tap the token, the FIDO2 "up" feature) when unlocking the volume. This option only applies when in manual mode, i.e. when fido2-cid= option is set. Defaults to neither true or false, but rather to v248 behavior, that is: try with no UP first, but if token reports that UP is required, try again with UP enabled. Added in version 257.

fido2-uv=

Controls whether to require user verification (the FIDO2 "uv" feature) when unlocking the volume. This option only applies when in manual mode, i.e. when fido2-cid= option is set. Defaults to neither true or false, but rather to v248 behavior, that is: omit configuring UV whatsoever. Added in version 257.

tpm2-device=

Takes either the special value "auto" or the path to a device node (e.g. /dev/tpmrm0) referring to a TPM2 security chip. See below for an example how to set up this mechanism for unlocking an encrypted volume with a TPM2 chip. Use tpm2-pcrs= (see below) to configure the set of TPM2 PCRs to bind the volume unlocking to. Use systemd-cryptenroll(1) as simple tool for enrolling TPM2 security chips in LUKS2 volumes.

If specified as "auto" the TPM2 device is automatically discovered. Use systemd-cryptenroll --tpm2-device=list to list all suitable TPM2 devices currently available, along with their device nodes.

This option implements the following mechanism: when enrolling a TPM2 device via systemd-cryptenroll on a LUKS2 volume, a randomized key unlocking the volume is generated on the host and loaded into the TPM2 chip where it is encrypted with an asymmetric "primary" key pair derived from the TPM2's internal "seed" key. Neither the seed key nor the primary key are permitted to ever leave the TPM2 chip — however, the now encrypted randomized key may. It is saved in the LUKS2 volume JSON token header. When unlocking the encrypted volume, the primary key pair is generated on the TPM2 chip again (which works as long as the chip's seed key is correctly maintained by the TPM2 chip), which is then used to decrypt (on the TPM2 chip) the encrypted key from the LUKS2 volume JSON token header saved there during enrollment. The resulting decrypted key is then used to unlock the volume. When the randomized key is encrypted the current values of the selected PCRs (see below) are included in the operation, so that different PCR state results in different encrypted keys and the decrypted key can only be recovered if the same PCR state is reproduced.

Added in version 248.

tpm2-pcrs=

Takes a "+" separated list of numeric TPM2 PCR (i.e. "Platform Configuration Register") indexes to bind the TPM2 volume unlocking to. This option is only useful when TPM2 enrollment metadata is not available in the LUKS2 JSON token header already, the way systemd-cryptenroll writes it there. If not used (and no metadata in the LUKS2 JSON token header defines it), defaults to a list of a single entry: PCR 7. Assign an empty string to encode a policy that binds the key to no PCRs, making the key accessible to local programs regardless of the current PCR state. Added in version 248.

tpm2-pin=

Takes a boolean argument, defaults to "false". Controls whether TPM2 volume unlocking is bound to a PIN in addition to PCRs. Similarly, this option is only useful when TPM2 enrollment metadata is not available. Added in version 251.

tpm2-signature=

Takes an absolute path to a TPM2 PCR JSON signature file, as produced by the systemd-measure(1) tool. This permits locking LUKS2 volumes to any PCR values for which a valid signature matching a public key specified at key enrollment time can be provided. See systemd-cryptenroll(1) for details on enrolling TPM2 PCR public keys. If this option is not specified but it is attempted to unlock a LUKS2 volume with a signed TPM2 PCR enrollment, a suitable signature file tpm2-pcr-signature.json is searched for in /etc/systemd/, /run/systemd/, /usr/lib/systemd/ (in this order). Added in version 252.

tpm2-pcrlock=

Takes an absolute path to a TPM2 pcrlock policy file, as produced by the systemd-pcrlock(8) tool. This permits locking LUKS2 volumes to a local policy of allowed PCR values with variants. See systemd-cryptenroll(1) for details on enrolling TPM2 pcrlock policies. If this option is not specified but it is attempted to unlock a LUKS2 volume with a TPM2 pcrlock enrollment, a suitable signature file pcrlock.json is searched for in /run/systemd/ and /var/lib/systemd/ (in this order). Added in version 255.

tpm2-measure-pcr=

Controls whether to measure the volume key of the encrypted volume to a TPM2 PCR. If set to "no" (which is the default) no PCR extension is done. If set to "yes" the volume key is measured into PCR 15. If set to a decimal integer in the range 0...23 the volume key is measured into the specified PCR. The volume key is measured along with the activated volume name and its UUID. This functionality is particularly useful for the encrypted volume backing the root file system, as it then allows later TPM objects to be securely bound to the root file system and hence the specific installation. Added in version 253.

tpm2-measure-bank=

Selects one or more TPM2 PCR banks to measure the volume key into, as configured with tpm2-measure-pcr= above. Multiple banks may be specified, separated by a colon character. If not specified, automatically determines available and used banks. Expects a message digest name (e.g. "sha1", "sha256", ...) as argument, to identify the bank. Added in version 253.

token-timeout=

Specifies how long to wait at most for configured security devices (i.e. FIDO2, PKCS#11, TPM2) to show up. Takes a time value in seconds (but other time units may be specified too, see systemd.time(7) for supported formats). Defaults to 30s. Once the specified timeout elapsed authentication via password is attempted. Note that this timeout applies to waiting for the security device to show up — it does not apply to the PIN prompt for the device (should one be needed) or similar. Pass 0 to turn off the timeout and wait forever. Added in version 250.

try-empty-password=

Takes a boolean argument. If enabled, right before asking the user for a password it is first attempted to unlock the volume with an empty password. This is useful for systems that are initialized with an encrypted volume with only an empty password set, which shall be replaced with a suitable password during first boot, but after activation. Added in version 246.

x-systemd.device-timeout=

Specifies how long systemd should wait for a block device to show up before giving up on the entry. The argument is a time in seconds or explicitly specified units of "s", "min", "h", "ms". Added in version 216.

x-initrd.attach

Setup this encrypted block device in the initrd, similarly to systemd.mount(5) units marked with x-initrd.mount. Although it is not necessary to mark the mount entry for the root file system with x-initrd.mount, x-initrd.attach is still recommended with the encrypted block device containing the root file system as otherwise systemd will attempt to detach the device during the regular system shutdown while it is still in use. With this option the device will still be detached but later after the root file system is unmounted.

All other encrypted block devices that contain file systems mounted in the initrd should use this option.

Added in version 245.

At early boot and when the system manager configuration is reloaded, this file is translated into native systemd units by systemd-cryptsetup-generator(8).

## AF_UNIX KEY FILES
If the key file path (as specified in the third column of /etc/crypttab entries, see above) refers to an AF_UNIX stream socket in the file system, the key is acquired by connecting to the socket and reading the key from the connection. The connection is made from an AF_UNIX socket name in the abstract namespace, see unix(7) for details. The source socket name is chosen according to the following format:

```
NUL RANDOM /cryptsetup/ VOLUME
```

In other words: a NUL byte (as required for abstract namespace sockets), followed by a random string (consisting of alphanumeric characters only), followed by the literal string "/cryptsetup/", followed by the name of the volume to acquire they key for. For example, for the volume "myvol":

```
\0d7067f78d9827418/cryptsetup/myvol
```

Services listening on the AF_UNIX stream socket may query the source socket name with getpeername(2), and use this to determine which key to send, allowing a single listening socket to serve keys for multiple volumes. If the PKCS#11 logic is used (see above), the socket source name is picked in similar fashion, except that the literal string "/cryptsetup-pkcs11/" is used. And similarly for FIDO2 ("/cryptsetup-fido2-salt/") and TPM2 ("/cryptsetup-tpm2/"). A different path component is used so that services providing key material know that the secret key was not requested directly, but instead an encrypted key that will be decrypted via the PKCS#11/FIDO2/TPM2 logic to acquire the final secret key.

## EXAMPLES
Example 1. /etc/crypttab example

Set up four encrypted block devices. One using LUKS for normal storage, another one for usage as a swap device and two TrueCrypt volumes. For the fourth device, the option string is interpreted as two options "cipher=xchacha12,aes-adiantum-plain64", "keyfile-timeout=10s".

```
luks       UUID=2505567a-9e27-4efe-a4d5-15ad146c258b
swap       /dev/sda7       /dev/urandom       swap
truecrypt  /dev/sda2       /etc/container_password  tcrypt
hidden     /mnt/tc_hidden  /dev/null    tcrypt-hidden,tcrypt-keyfile=/etc/keyfile
external   /dev/sda3       keyfile:LABEL=keydev keyfile-timeout=10s,cipher=xchacha12\,aes-adiantum-plain64
```

Example 2. Yubikey-based PKCS#11 Volume Unlocking Example

The PKCS#11 logic allows hooking up any compatible security token that is capable of storing RSA or EC cryptographic keys for unlocking an encrypted volume. Here's an example how to set up a Yubikey security token for this purpose on a LUKS2 volume, using ykmap(1) from the yubikey-manager project to initialize the token and systemd-cryptenroll(1) to add it in the LUKS2 volume:

```
# SPDX-License-Identifier: MIT-0
# Destroy any old key on the Yubikey (careful!)
ykman piv reset
# Generate a new private/public key pair on the device, store the public key in
# 'pubkey.pem'.
ykman piv generate-key -a RSA2048 9d pubkey.pem
# Create a self-signed certificate from this public key, and store it on the
# device. The "subject" should be an arbitrary user-chosen string to identify
# the token with.
ykman piv generate-certificate --subject "Knobelei" 9d pubkey.pem
# We do not need the public key anymore, let's remove it. Since it is not
# security sensitive we just do a regular "rm" here.
rm pubkey.pem
# Enroll the freshly initialized security token in the LUKS2 volume. Replace
# /dev/sdXn by the partition to use (e.g. /dev/sda1).
sudo systemd-cryptenroll --pkcs11-token-uri=auto /dev/sdXn
# Test: Let's run systemd-cryptsetup to test if this all worked.
sudo systemd-cryptsetup attach mytest /dev/sdXn - pkcs11-uri=auto
# If that worked, let's now add the same line persistently to /etc/crypttab,
# for the future. We do not want to use the (unstable) /dev/sdX name, so let's
# figure out a stable link:
udevadm info -q -r symlink /dev/sdXn
# Now add the line using the by-uuid symlink to /etc/crypttab:
sudo bash -c 'echo "mytest /dev/disk/by-uuid/... - pkcs11-uri=auto" >>/etc/crypttab'
# Depending on your distribution and encryption setup, you may need to manually
# regenerate your initramfs to be able to use a Yubikey / PKCS#11 token to
# unlock the partition during early boot.
# More information at https://unix.stackexchange.com/a/705809.
# On Fedora based systems:
sudo dracut --force
# On Debian based systems:
sudo update-initramfs -u
```

A few notes on the above:

•We use RSA2048, which is the longest key size current Yubikeys support

•We use Yubikey key slot 9d, since that's apparently the keyslot to use for decryption purposes, see Yubico PIV certificate slots[3].

Example 3. FIDO2 Volume Unlocking Example

The FIDO2 logic allows using any compatible FIDO2 security token that implements the "hmac-secret" extension for unlocking an encrypted volume. Here's an example how to set up a FIDO2 security token for this purpose for a LUKS2 volume, using systemd-cryptenroll(1):

```
# SPDX-License-Identifier: MIT-0
# Enroll the security token in the LUKS2 volume. Replace /dev/sdXn by the
# partition to use (e.g. /dev/sda1).
sudo systemd-cryptenroll --fido2-device=auto /dev/sdXn
# Test: Let's run systemd-cryptsetup to test if this worked.
sudo systemd-cryptsetup attach mytest /dev/sdXn - fido2-device=auto
# If that worked, let's now add the same line persistently to /etc/crypttab,
# for the future. We do not want to use the (unstable) /dev/sdX name, so let's
# figure out a stable link:
udevadm info -q -r symlink /dev/sdXn
# Now add the line using the by-uuid symlink to /etc/crypttab:
sudo bash -c 'echo "mytest /dev/disk/by-uuid/... - fido2-device=auto" >>/etc/crypttab'
# Depending on your distribution and encryption setup, you may need to manually
# regenerate your initramfs to be able to use a FIDO2 device to unlock the
# partition during early boot.
# More information at https://unix.stackexchange.com/a/705809.
# On Fedora based systems:
sudo dracut --force
# On Debian based systems:
sudo update-initramfs -u
```

Example 4. TPM2 Volume Unlocking Example

The TPM2 logic allows using any TPM2 chip supported by the Linux kernel for unlocking an encrypted volume. Here's an example how to set up a TPM2 chip for this purpose for a LUKS2 volume, using systemd-cryptenroll(1):

```
# SPDX-License-Identifier: MIT-0
# Enroll the TPM2 security chip in the LUKS2 volume, and bind it to PCR 7
# only. Replace /dev/sdXn by the partition to use (e.g. /dev/sda1).
sudo systemd-cryptenroll --tpm2-device=auto --tpm2-pcrs=7 /dev/sdXn
# Test: Let's run systemd-cryptsetup to test if this worked.
sudo systemd-cryptsetup attach mytest /dev/sdXn - tpm2-device=auto
# If that worked, let's now add the same line persistently to /etc/crypttab,
# for the future. We do not want to use the (unstable) /dev/sdX name, so let's
# figure out a stable link:
udevadm info -q -r symlink /dev/sdXn
# Now add the line using the by-uuid symlink to /etc/crypttab:
sudo bash -c 'echo "mytest /dev/disk/by-uuid/... - tpm2-device=auto" >>/etc/crypttab'
# And now let's check that automatic unlocking works:
sudo systemd-cryptsetup detach mytest
sudo systemctl daemon-reload
sudo systemctl start cryptsetup.target
systemctl is-active systemd-cryptsetup@mytest.service
# Once we have the device which will be unlocked automatically, we can use it.
# Usually we would create a file system and add it to /etc/fstab:
sudo mkfs.ext4 /dev/mapper/mytest
# This prints a 'Filesystem UUID', which we can use as a stable name:
sudo bash -c 'echo "/dev/disk/by-uuid/... /var/mytest ext4 defaults,x-systemd.mkdir 0 2" >>/etc/fstab'
# And now let's check that the mounting works:
sudo systemctl daemon-reload
sudo systemctl start /var/mytest
systemctl status /var/mytest
# Depending on your distribution and encryption setup, you may need to manually
# regenerate your initramfs to be able to use a TPM2 security chip to unlock
# the partition during early boot.
# More information at https://unix.stackexchange.com/a/705809.
# On Fedora based systems:
sudo dracut --force
# On Debian based systems:
sudo update-initramfs -u
```

## SEE ALSO
systemd(1), systemd-cryptsetup@.service(8), systemd-cryptsetup-generator(8), systemd-cryptenroll(1), fstab(5), cryptsetup(8), mkswap(8), mke2fs(8)

## NOTES
1.

Veracrypt Personal Iterations Multiplier

https://www.veracrypt.fr/en/Personal%20Iterations%20Multiplier%20%28PIM%29.html

2.

RFC7512 PKCS#11 URI

https://tools.ietf.org/html/rfc7512

3.

Yubico PIV certificate slots

https://developers.yubico.com/PIV/Introduction/Certificate_slots.html


environment.d

title: environment.d(5)

summary: Definition of user service environment

text:
# environment.d(5)

## NAME
environment.d - Definition of user service environment

## SYNOPSIS
~/.config/environment.d/*.conf

/etc/environment.d/*.conf

/run/environment.d/*.conf

/usr/local/lib/environment.d/*.conf

/usr/lib/environment.d/*.conf

/etc/environment

## DESCRIPTION
Configuration files in the environment.d/ directories contain lists of environment variable assignments passed to services started by the systemd user instance. systemd-environment-d-generator(8) parses them and updates the environment exported by the systemd user instance. See below for an discussion of which processes inherit those variables.

It is recommended to use numerical prefixes for file names to simplify ordering.

For backwards compatibility, a symlink to /etc/environment is installed, so this file is also parsed.

## CONFIGURATION DIRECTORIES AND PRECEDENCE
Configuration files are read from directories in /etc/, /run/, /usr/local/lib/, and /usr/lib/, in order of precedence, as listed in the SYNOPSIS section above. Files must have the ".conf" extension. Files in /etc/ override files with the same name in /run/, /usr/local/lib/, and /usr/lib/. Files in /run/ override files with the same name under /usr/.

All configuration files are sorted by their filename in lexicographic order, regardless of which of the directories they reside in. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Thus, the configuration in a certain file may either be replaced completely (by placing a file with the same name in a directory with higher priority), or individual settings might be changed (by specifying additional settings in a file with a different name that is ordered later).

Packages should install their configuration files in /usr/lib/ (distribution packages) or /usr/local/lib/ (local installs) [1]. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages.

It is recommended to prefix all filenames with a two-digit number and a dash to simplify the ordering. It is recommended to use the range 10-40 for configuration files in /usr/ and the range 60-90 for configuration files in /etc/ and /run/, to make sure that local and transient configuration files will always take priority over configuration files shipped by the OS vendor.

If the administrator wants to disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in the configuration directory in /etc/, with the same filename as the vendor configuration file. If the vendor configuration file is included in the initrd image, the image has to be regenerated.

## CONFIGURATION FORMAT
The configuration files contain a list of "KEY=VALUE" environment variable assignments, separated by newlines. The right hand side of these assignments may reference previously defined environment variables, using the "${OTHER_KEY}" and "$OTHER_KEY" format. It is also possible to use "${FOO:-DEFAULT_VALUE}" to expand in the same way as "${FOO}" unless the expansion would be empty, in which case it expands to DEFAULT_VALUE, and use "${FOO:+ALTERNATE_VALUE}" to expand to ALTERNATE_VALUE as long as "${FOO}" would have expanded to a non-empty value. No other elements of shell syntax are supported.

Each KEY must be a valid variable name. Empty lines and lines beginning with the comment character "#" are ignored.

### Example
Example 1. Setup environment to allow access to a program installed in /opt/foo

/etc/environment.d/60-foo.conf:

```
        FOO_DEBUG=force-software-gl,log-verbose

        PATH=/opt/foo/bin:$PATH

        LD_LIBRARY_PATH=/opt/foo/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}

        XDG_DATA_DIRS=/opt/foo/share:${XDG_DATA_DIRS:-/usr/local/share/:/usr/share/}
```

## APPLICABILITY
Environment variables exported by the user service manager (systemd --user instance started in the user@uid.service system service) are passed to any services started by that service manager. In particular, this may include services which run user shells. For example in the GNOME environment, the graphical terminal emulator runs as the gnome-terminal-server.service user unit, which in turn runs the user shell, so that shell will inherit environment variables exported by the user manager. For other instances of the shell, not launched by the user service manager, the environment they inherit is defined by the program that starts them. Hint: in general, systemd.service(5) units contain programs launched by systemd, and systemd.scope(5) units contain programs launched by something else.

Note that these files do not affect the environment block of the service manager itself, but exclusively the environment blocks passed to the services it manages. Environment variables set that way thus cannot be used to influence behaviour of the service manager. In order to make changes to the service manager's environment block the environment must be modified before the user's service manager is invoked, for example from the system service manager or via a PAM module.

Specifically, for ssh logins, the sshd(8) service builds an environment that is a combination of variables forwarded from the remote system and defined by sshd, see the discussion in ssh(1). A graphical display session will have an analogous mechanism to define the environment. Note that some managers query the systemd user instance for the exported environment and inject this configuration into programs they start, using systemctl show-environment or the underlying D-Bus call.

## SEE ALSO
systemd(1), systemd-environment-d-generator(8), systemd.environment-generator(7)

## NOTES
1.

💣💥🧨💥💥💣 Please note that those configuration files must be available at all times. If /usr/local/ is a separate partition, it may not be available during early boot, and must not be used for configuration.


hostname

title: hostname(5)

summary: Local hostname configuration file

text:
# hostname(5)

## NAME
hostname - Local hostname configuration file

## SYNOPSIS
/etc/hostname

## DESCRIPTION
The /etc/hostname file configures the name of the local system. Unless overridden as described in the next section, systemd(1) will set this hostname during boot using the sethostname(2) system call.

The file should contain a single newline-terminated hostname string. Comments (lines starting with a "#") are ignored. The hostname should be composed of up to 64 7-bit ASCII lower-case alphanumeric characters or hyphens forming a valid DNS domain name. It is recommended that this name contains only a single label, i.e. without any dots. Invalid characters will be filtered out in an attempt to make the name valid, but obviously it is recommended to use a valid name and not rely on this filtering.

You may use hostnamectl(1) to change the value of this file during runtime from the command line. Use systemd-firstboot(1) to initialize it on mounted (but not booted) system images.

## HOSTNAME SEMANTICS
systemd(1) and the associated tools will obtain the hostname in the following ways:

•If the kernel command line parameter systemd.hostname= specifies a valid hostname, systemd(1) will use it to set the hostname during early boot, see kernel-command-line(7),

•Otherwise, the "static" hostname specified by /etc/hostname as described above will be used.

•Otherwise, a transient hostname may be set during runtime, for example based on information in a DHCP lease, see systemd-hostnamed.service(8). Both NetworkManager[1] and systemd-networkd.service(8) allow this. Note that systemd-hostnamed.service(8) gives higher priority to the static hostname, so the transient hostname will only be used if the static hostname is not configured.

•Otherwise, a fallback hostname configured at compilation time will be used ("localhost").

Effectively, the static hostname has higher priority than a transient hostname, which has higher priority than the fallback hostname. Transient hostnames are equivalent, so setting a new transient hostname causes the previous transient hostname to be forgotten. The hostname specified on the kernel command line is like a transient hostname, with the exception that it has higher priority when the machine boots. Also note that those are the semantics implemented by systemd tools, but other programs may also set the hostname.

## HISTORY
The simple configuration file format of /etc/hostname originates from Debian GNU/Linux.

## SEE ALSO
systemd(1), sethostname(2), hostname(1), hostname(7), machine-id(5), machine-info(5), hostnamectl(1), systemd-hostnamed.service(8), systemd-firstboot(1)

## NOTES
1.

NetworkManager

https://developer.gnome.org/NetworkManager/stable/


integritytab

title: integritytab(5)

text:
# integritytab(5)

## NAME
integritytab - Configuration for integrity block devices

## SYNOPSIS
/etc/integritytab

## DESCRIPTION
The /etc/integritytab file describes integrity protected block devices that are set up during system boot.

Empty lines and lines starting with the "#" character are ignored. Each of the remaining lines describes one verity integrity protected block device. Fields are delimited by white space.

Each line is in the form

```
volume-name block-device

    [keyfile|-] [options|-]
```

The first two fields are mandatory, the remaining two are optional and only required if user specified non-default options during integrity format.

The first field contains the name of the resulting integrity volume; its block device is set up below /dev/mapper/.

The second field contains a path to the underlying block device, or a specification of a block device via "UUID=" followed by the UUID, "PARTUUID=" followed by the partition UUID, "LABEL=" followed by the label, "PARTLABEL=" followed by the partition label.

The third field if present contains an absolute filename path to a key file or a "-" to specify none. When the filename is present, the "integrity-algorithm" defaults to "hmac-sha256" with the key length derived from the number of bytes in the key file. At this time the only supported integrity algorithm when using key file is hmac-sha256. The maximum size of the key file is 4096 bytes.

The fourth field, if present, is a comma-delimited list of options or a "-" to specify none. The following options are recognized:

allow-discards

Allow the use of discard (TRIM) requests for the device. This option is available since the Linux kernel version 5.7. Added in version 250.

mode=(journal|bitmap|direct)

Enable journaled, bitmapped or direct (passthrough) mode. Journaled mode is the default when this option is not specified. It provides safety against crashes, but can be slow because all data has to be written twice. Bitmap mode is more efficient since it requires only a single write, but it is less reliable because if data corruption happens when the machine crashes, it might not be detected. Direct mode disables the journal and the bitmap. Corresponds to the "direct writes" mode documented in the dm-integrity documentation[1]. Note that without a journal, if there is a crash, it is possible that the integrity tags and data will not match. If used, the journal-* options below will have no effect if passed. Added in version 254.

journal-watermark=[0..100]%

Journal watermark in percent. When the journal percentage exceeds this watermark, the journal flush will be started. Setting a value of "0%" uses default value. Added in version 250.

journal-commit-time=[0..N]

Commit time in milliseconds. When this time passes (and no explicit flush operation was issued), the journal is written. Setting a value of zero uses default value. Added in version 250.

data-device=/dev/disk/by-...

Specify a separate block device that contains existing data. The second field specified in the integritytab for block device then will contain calculated integrity tags and journal for data-device, but not the end user data. Added in version 250.

integrity-algorithm=[crc32c|crc32|xxhash64|sha1|sha256|hmac-sha256]

The algorithm used for integrity checking. The default is crc32c. Must match option used during format. Added in version 250.

At early boot and when the system manager configuration is reloaded, this file is translated into native systemd units by systemd-integritysetup-generator(8).

## EXAMPLES
Example 1. /etc/integritytab

Set up two integrity protected block devices.

```
home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - journal-commit-time=10,allow-discards,journal-watermark=55%
data PARTUUID=5d4b1808-be76-774d-88af-03c4c3a41761 - allow-discards
```

Example 2. /etc/integritytab

Set up 1 integrity protected block device using defaults

```
home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8
```

Example 3. /etc/integritytab

Set up 1 integrity device using existing data block device which contains user data

```
home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - data-device=/dev/disk/by-uuid/9276d9c0-d4e3-4297-b4ff-3307cd0d092f
```

Example 4. /etc/integritytab

Set up 1 integrity device using a HMAC key file using defaults

```
home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 /etc/hmac.key
```

## SEE ALSO
systemd(1), systemd-integritysetup@.service(8), systemd-integritysetup-generator(8), integritysetup(8)

## NOTES
1.

the dm-integrity documentation

https://docs.kernel.org/admin-guide/device-mapper/dm-integrity.html