.\" Copyright (c) 2025 Chengyu Zhu <hudsonzhu@tencent.com>
.\"
.TH MOUNT.EROFS 8
.SH NAME
mount.erofs \- manage EROFS filesystem
.SH SYNOPSIS
\fBmount.erofs\fR [\fIOPTIONS\fR] \fISOURCE\fR \fIMOUNTPOINT\fR
.br
\fBmount.erofs\fR \fB\-u\fR \fITARGET\fR
.br
\fBmount.erofs\fR \fB\-\-reattach\fR \fITARGET\fR
.SH DESCRIPTION
EROFS is an enhanced lightweight read-only filesystem with modern designs
for scenarios which need high-performance read-only requirements.
.PP
\fBmount.erofs\fR is used to mount an EROFS filesystem from \fISOURCE\fR
(which can be an image file or block device) to a \fIMOUNTPOINT\fR. It supports multiple backends including
direct kernel mount, FUSE-based mount, and NBD (Network Block Device) for
remote sources like OCI images.
.SH OPTIONS
.TP
.B \-h, \-\-help
Display help message and exit.
.TP
.B \-V, \-\-version
Display version information and exit.
.TP
.BI "\-o " options
Comma-separated list of mount options. See \fBMOUNT OPTIONS\fR below.
.TP
.BI "\-t " type[.subtype]
Specify the filesystem type and optional subtype. The type should be
\fBerofs\fR. Available subtypes are:
.RS
.TP
.B fuse
Use FUSE-based mount via \fBerofsfuse\fR.
.TP
.B local
Force direct kernel mount (default if available).
.TP
.B nbd
Use NBD backend for remote sources (e.g., OCI images).
.RE
.TP
.B \-u
Unmount the filesystem at the specified target.
.TP
.B \-\-reattach
Reattach to an existing NBD device and restart the NBD service.
.SH MOUNT OPTIONS
Standard mount options:
.TP
.B ro
Mount the filesystem read-only (default).
.TP
.B rw
Mount the filesystem read-write (not supported for EROFS).
.TP
.B nosuid
Do not honor set-user-ID and set-group-ID bits.
.TP
.B suid
Honor set-user-ID and set-group-ID bits (default).
.TP
.B nodev
Do not interpret character or block special devices.
.TP
.B dev
Interpret character or block special devices (default).
.TP
.B noexec
Do not allow direct execution of any binaries.
.TP
.B exec
Allow execution of binaries (default).
.TP
.B noatime
Do not update inode access times.
.TP
.B atime
Update inode access times (default).
.TP
.B nodiratime
Do not update directory inode access times.
.TP
.B diratime
Update directory inode access times (default).
.TP
.B relatime
Update inode access times relative to modify or change time.
.TP
.B norelatime
Do not use relative atime updates.
.SH OCI-SPECIFIC OPTIONS
The following OCI-specific options are available:
.TP
.BI "oci.blob=" digest
Specify the OCI blob digest to mount. The digest should be in the format
\fBsha256:...\fR. Cannot be used together with \fBoci.layer\fR.
.TP
.BI "oci.layer=" index
Specify the OCI layer index to mount (0-based). Cannot be used together
with \fBoci.blob\fR.
.TP
.BI "oci.platform=" platform
Specify the target platform (default: \fBlinux/amd64\fR).
.TP
.BI "oci.username=" username
Username for OCI registry authentication.
.TP
.BI "oci.password=" password
Password for OCI registry authentication.
.TP
.BI "oci.tarindex=" path
Path to a tarball index file for hybrid tar+OCI mode.
.TP
.BI "oci.zinfo=" path
Path to a gzip zinfo file for random access to gzip-compressed tar layers.
.TP
.BI "oci.insecure"
Use HTTP instead of HTTPS to access the image registry.
.SH NOTES
.IP \(bu 2
EROFS filesystems are read-only by nature. The \fBrw\fR option will be ignored.
.IP \(bu 2
When mounting OCI images via NBD, the mount process creates a background
daemon to serve the NBD device. The daemon will automatically clean up when
the filesystem is unmounted.
.IP \(bu 2
The \fB\-\-reattach\fR option is useful for recovering NBD mounts after a
system crash or when the NBD daemon was terminated unexpectedly.
.IP \(bu 2
Kernel direct mount is used when mounting a regular file without
specifying a backend type. If file-based mounts is unsupported,
loop devices will be set up automatically.
.SH SEE ALSO
.BR mkfs.erofs (1),
.BR erofsfuse (1),
.BR dump.erofs (1),
.BR fsck.erofs (1),
.BR mount (8),
.BR umount (8)
.SH AVAILABILITY
\fBmount.erofs\fR is part of erofs-utils.