borg-mount(1)

Name
borg-mount - Mounts an archive or an entire repository as a FUSE filesystem.

SYNOPSIS

borg [common options] mount [options] MOUNTPOINT [PATH...]

DESCRIPTION

This command mounts a repository or an archive as a FUSE filesystem. This can be useful for browsing or restoring individual files.

When restoring, take into account that the current FUSE implementation does not support special fs flags. On Linux, POSIX ACLs of the archived fs objects are exposed (read-only) via the system.posix_acl_access and system.posix_acl_default extended attributes, so tools like getfacl or rsync -A can read them from the mounted archive. Note that the mount does not enforce the ACLs for permission checks. On other platforms, ACLs are not supported.

When mounting a repository, there is one top directory per archive and the directory structure below these will be loaded on-demand from the repository when entering these directories, so expect some delay.

By default, these top directories are named like the archives; as the archives of a series all have the same name, -{id:.8} (the first 8 hex digits of the archive id) is appended whenever a name is not unique. To name them differently, set the BORG_MOUNT_ARCHIVE_DIR_FORMAT environment variable to a format string using the placeholders of borg repo-list --format, e.g. {name}-{time:%Y-%m-%dT%H:%M:%S} or {hostname}-{name}; names that are still not unique get -{id:.8} appended.

Note: Borg stores symbolic links as-is. Consequently, when an archive or repository is mounted, symbolic links may resolve to locations outside of the mountpoint, either because they are absolute or because relative links traverse outside of the mounted tree.

Normal UNIX pathname resolution applies: most tools follow symbolic links by default and may therefore access files or directories that are not part of the mounted archive. Consequently, operations intended to inspect archived data may instead access "live" data from the host filesystem.

On Linux, this can be prevented by remounting the mountpoint with the nosymfollow VFS mount option, for example: borg mount <repo path> <mountpoint> mount -o remount,nosymfollow <repo path> <mountpoint>

Alternatively, access the mounted archive from an appropriately isolated environment (for example, a container or chroot).

Unless the --foreground option is given, the command will run in the background until the filesystem is unmounted.

Performance tips:

•   When doing a "whole repository" mount: do not enter archive directories if not needed; this avoids on-demand loading.

•   Only mount a specific archive, not the whole repository.

•   Only mount specific paths in a specific archive, not the complete archive.

    The command borgfs provides a wrapper for borg mount. This can also be used in fstab entries: /path/to/repo /mnt/point fuse.borgfs defaults,noauto 0 0

    To allow a regular user to use fstab entries, add the user option: /path/to/repo /mnt/point fuse.borgfs defaults,noauto,user 0 0

    For FUSE configuration and mount options, see the mount.fuse(8) manual page.

    Borg's default behavior is to use the archived user and group names of each file and map them to the system's respective user and group IDs. Alternatively, using numeric-ids will instead use the archived user and group IDs without any mapping.

    The uid and gid mount options (implemented by Borg) can be used to override the user and group IDs of all files (i.e., borg mount -o uid=1000,gid=1000).

    The man page references user_id and group_id mount options (implemented by FUSE) which specify the user and group ID of the mount owner (also known as the user who does the mounting). It is set automatically by libfuse (or the filesystem if libfuse is not used). However, you should not specify these manually. Unlike the uid and gid mount options, which affect all files, user_id and group_id affect the user and group ID of the mounted (base) directory.

    Additional mount options supported by Borg:

•   versions: when used with a repository mount, this gives a merged, versioned view of the files in the archives. EXPERIMENTAL; layout may change in the future.

•   allow_damaged_files: by default, damaged files (where chunks are missing) will return EIO (I/O error) when trying to read the related parts of the file. Set this option to replace the missing parts with all-zero bytes.

•   ignore_permissions: for security reasons the default_permissions mount option is internally enforced by Borg. ignore_permissions can be given to not enforce default_permissions.

    The BORG_MOUNT_DATA_CACHE_ENTRIES environment variable is intended for advanced users to tweak performance. It sets the number of cached data chunks; additional memory usage can be up to ~8 MiB times this number. The default is the number of CPU cores.

    When the daemonized process receives a signal or crashes, it does not unmount. Unmounting in these cases could cause an active rsync or similar process to delete data unintentionally.

    When running in the foreground, ^C/SIGINT cleanly unmounts the filesystem, but other signals or crashes do not.

    Debugging:

    borg mount usually daemonizes and the daemon process sends stdout/stderr to /dev/null. Thus, you need to either use -f / --foreground to make it stay in the foreground and not daemonize, or use BORG_LOGGING_CONF to reconfigure the logger to output to a file.

OPTIONS

See borg-common(1) for common options of Borg commands.

  arguments

MOUNTPOINT
    where to mount the filesystem

PATH
    paths to extract; patterns are supported

  options

-f, --foreground
    stay in foreground, do not daemonize

-o  extra mount options

--numeric-ids
    use numeric user and group identifiers from archives

  Archive filters

-a PATTERN, --match-archives PATTERN
    only consider archives matching all patterns. See "borg help match-archives".

--sort-by KEYS
    Comma-separated list of sorting keys; valid keys are: timestamp, archive, name, id, tags, host, user; default is: timestamp

--first N
    consider the first N archives after other filters are applied

--last N
    consider the last N archives after other filters are applied

--oldest TIMESPAN
    consider archives between the oldest archive's timestamp and (oldest + TIMESPAN), e.g., 7d or 12m.

--newest TIMESPAN
    consider archives between the newest archive's timestamp and (newest - TIMESPAN), e.g., 7d or 12m.

--older TIMESPAN
    consider archives older than (now - TIMESPAN), e.g., 7d or 12m.

--newer TIMESPAN
    consider archives newer than (now - TIMESPAN), e.g., 7d or 12m.

  Include/Exclude options

-e PATTERN, --exclude PATTERN
    exclude paths matching PATTERN

--exclude-from EXCLUDEFILE
    read exclude patterns from EXCLUDEFILE, one per line

--pattern PATTERN
    include/exclude paths matching PATTERN

--patterns-from PATTERNFILE
    read include/exclude patterns from PATTERNFILE, one per line

--strip-components NUMBER
    Remove the specified number of leading path elements. Paths with fewer elements will be silently skipped.

SEE ALSO

borg-common(1), borg-umount(1), borg-extract(1)

Author
The Borg Collective