.nh
.TH mount.composefs(1) composefs | User Commands

.SH NAME
mount.composefs \- mount a composefs filesystem image


.SH SYNOPSIS
\fBmount.composefs\fP [-o OPTIONS] \fIIMAGE\fP \fITARGETDIR\fP


.SH 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.

.PP
\fBmount.composefs\fP 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 \fBmount -t composefs ...\fR\&.


.SH OPTIONS
The provided \fIIMAGE\fP argument must be a valid composefs (EROFS)
metadata image.  The \fITARGETDIR\fP will be used as a mount target.

.PP
\fBmount.composefs\fP accepts the following colon-separated mount
options when passed via the \fB-o OPTIONS\fR argument.
.TP
\fBbasedir\fP=\fIPATH\fP
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 \fBmkcomposefs --digest-store=PATH\fR\&.

Multiple paths can be specified, separated by \fB:\fR\&.

.TP
\fBdigest\fP=\fIDIGEST\fP
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 \fBverity\fP\&.

.TP
\fBidmap\fP=\fIPATH\fP
Specify a path to a user namespace whose ID mapping should be used.
The typical format for this type of path is \fB/proc/<pid>/ns/user\fR

.TP
\fBverity\fP
If this is specified, all files in the \fIIMAGE\fP 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.

.TP
\fBro\fP
Mounts the filesystem read-only. This is mainly useful when using
\fBupperdir\fP as unlayered composefs images are naturally readonly.

.TP
\fBrw\fP
Overrides a previous \fBro\fP option

.TP
\fBupperdir\fP
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.

.TP
\fBworkdir\fP
Specifies an overlayfs workdir to go with \fBupperdir\fP\&.


.SH SEE ALSO
\fBcomposefs-info(1)\fP, \fBmount.composefs(1)\fP

.PP
composefs upstream
\[la]https://github.com/containers/composefs\[ra]