NAME

mount.composefs - mount a composefs filesystem image

SYNOPSIS

mount.composefs [-o OPTIONS] IMAGE TARGETDIR

DESCRIPTION

The composefs project uses EROFS image file to store metadata, and one or more separate directories containing content-addressed backing data for regular files.

mount.composefs mounts such an EROFS file in combination with a given set of basedir at the specified location. It can be called directly, or as a mount helper by running mount -t composefst ....

OPTIONS

The provided IMAGE argument must be a valid composefs (EROFS) metadata image. The TARGETDIR will be used as a mount target.

mount.composefs accepts the following colon-separated mount options when passed via the -o OPTIONS argument.

basedir=PATH : This path will be used to resolve non-empty file references
stored in the composefs metadata image. A primary use case is to have
this be the same path provided to mkcomposefs --digest-store=PATH.

Multiple paths can be specified, separated by `:`.

digest=DIGEST : The image file is validated to have the specified fs-verity digest
before being used. This allows a chain of trust the ensures only
the expected data is ever visible in the mount.

This option also implies **verity**.

verity : If this is specified, all files in the IMAGE must specify an fs-verity
digest, and all the files in the base dirs must have a matching fs-verity
digest.

Note: This needs support for the overlayfs "verity" option in the
kernel, which was added in 6.6rc1.

ro : Mounts the filesystem read-only. This is mainly useful when using
upperdir as unlayered composefs images are naturally readonly.

rw : Overrides a previous ro option

upperdir : Specify an upper dir in the overlayfs mount that composefs uses. This allows
a writable layer on top of the composefs image. See overlayfs docs for details.

workdir : Specifies an overlayfs workdir to go with upperdir.

SEE ALSO

composefs-info(1), mount.composefs(1)

composefs upstream ⟨https://github.com/containers/composefs⟩