|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | AUTOMATIC DEPENDENCIES | FSTAB | OPTIONS | SEE ALSO | NOTES | COLOPHON |
|
|
|
SYSTEMD.MOUNT(5) systemd.mount SYSTEMD.MOUNT(5)
systemd.mount - Mount unit configuration
mount.mount
A unit configuration file whose name ends in ".mount" encodes
information about a file system mount point controlled and
supervised by systemd.
This man page lists the configuration options specific to this
unit type. See systemd.unit(5) for the common options of all unit
configuration files. The common configuration items are configured
in the generic [Unit] and [Install] sections. The mount specific
configuration options are configured in the [Mount] section.
Additional options are listed in systemd.exec(5), which define the
execution environment the mount(8) program is executed in, and in
systemd.kill(5), which define the way the processes are
terminated, and in systemd.resource-control(5), which configure
resource control settings for the processes of the service.
Note that the options User= and Group= are not useful for mount
units. systemd passes two parameters to mount(8); the values of
What= and Where=. When invoked in this way, mount(8) does not read
any options from /etc/fstab, and must be run as UID 0.
Mount units must be named after the mount point directories they
control. Example: the mount point /home/lennart must be configured
in a unit file home-lennart.mount. For details about the escaping
logic used to convert a file system path to a unit name, see
systemd.unit(5). Note that mount units cannot be templated, nor is
possible to add multiple names to a mount unit by creating
symlinks to its unit file.
Optionally, a mount unit may be accompanied by an automount unit,
to allow on-demand or parallelized mounting. See
systemd.automount(5).
Mount points created at runtime (independently of unit files or
/etc/fstab) will be monitored by systemd and appear like any other
mount unit in systemd. See /proc/self/mountinfo description in
proc(5).
Some file systems have special semantics as API file systems for
kernel-to-userspace and userspace-to-userspace interfaces. Some of
them may not be changed via mount units, and cannot be disabled.
For a longer discussion see API File Systems[1].
The systemd-mount(1) command allows creating .mount and .automount
units dynamically and transiently from the command line.
Implicit Dependencies
The following dependencies are implicitly added:
• If a mount unit is beneath another mount unit in the file
system hierarchy, both a requirement dependency and an
ordering dependency between both units are created
automatically.
• Block device backed file systems automatically gain Requires=,
StopPropagatedFrom=, and After= type dependencies on the
device unit encapsulating the block device (see
x-systemd.device-bound= for details).
• If traditional file system quota is enabled for a mount unit,
automatic Wants= and Before= dependencies on
[email protected] and [email protected] are added.
• Additional implicit dependencies may be added as result of
execution and resource control parameters as documented in
systemd.exec(5) and systemd.resource-control(5).
Default Dependencies
The following dependencies are added unless DefaultDependencies=no
is set:
• All mount units acquire automatic Before= and Conflicts= on
umount.target in order to be stopped during shutdown.
• Mount units referring to local file systems automatically gain
an After= dependency on local-fs-pre.target, and a Before=
dependency on local-fs.target unless one or more mount options
among nofail, x-systemd.wanted-by=, and x-systemd.required-by=
is set. See below for detailed information.
Additionally, an After= dependency on swap.target is added
when the file system type is "tmpfs".
• Network mount units automatically acquire After= dependencies
on remote-fs-pre.target, network.target, plus After= and
Wants= dependencies on network-online.target, and a Before=
dependency on remote-fs.target, unless one or more mount
options among nofail, x-systemd.wanted-by=, and
x-systemd.required-by= is set.
Mount units referring to local and network file systems are
distinguished by their file system type specification. In some
cases this is not sufficient (for example network block device
based mounts, such as iSCSI), in which case _netdev may be added
to the mount option string of the unit, which forces systemd to
consider the mount unit a network mount.
Mount units may either be configured via unit files, or via
/etc/fstab (see fstab(5) for details). Mounts listed in /etc/fstab
will be converted into native units dynamically at boot and when
the configuration of the system manager is reloaded. In general,
configuring mount points through /etc/fstab is the preferred
approach to manage mounts for humans. For tooling, writing mount
units should be preferred over editing /etc/fstab. See
systemd-fstab-generator(8) for details about the conversion from
/etc/fstab to mount units.
The NFS mount option bg for NFS background mounts as documented in
nfs(5) is detected by systemd-fstab-generator and the options are
transformed so that systemd fulfills the job-control implications
of that option. Specifically systemd-fstab-generator acts as
though "x-systemd.mount-timeout=infinity,retry=10000" was
prepended to the option list, and "fg,nofail" was appended.
Depending on specific requirements, it may be appropriate to
provide some of these options explicitly, or to make use of the
"x-systemd.automount" option described below instead of using
"bg".
When reading /etc/fstab a few special mount options are understood
by systemd which influence how dependencies are created for mount
points. systemd will create a dependency of type Wants= or
Requires= (see option nofail below), from either local-fs.target
or remote-fs.target, depending whether the file system is local or
remote.
x-systemd.requires=
Configures a Requires= and an After= dependency between the
created mount unit and another systemd unit, such as a device
or mount unit. The argument should be a unit name, or an
absolute path to a device node or mount point. This option may
be specified more than once. This option is particularly
useful for mount point declarations that need an additional
device to be around (such as an external journal device for
journal file systems) or an additional mount to be in place
(such as an overlay file system that merges multiple mount
points). See After= and Requires= in systemd.unit(5) for
details.
Note that this option always applies to the created mount unit
only regardless whether x-systemd.automount has been
specified.
Added in version 220.
x-systemd.wants=
Configures a Wants= and an After= dependency between the
created mount unit and another systemd unit, similar to the
x-systemd.requires= option.
Added in version 257.
x-systemd.before=, x-systemd.after=
In the created mount unit, configures a Before= or After=
dependency on another systemd unit, such as a mount unit. The
argument should be a unit name or an absolute path to a mount
point. This option may be specified more than once. This
option is particularly useful for mount point declarations
with nofail option that are mounted asynchronously but need to
be mounted before or after some unit start, for example,
before local-fs.target unit. See Before= and After= in
systemd.unit(5) for details.
Note that these options always apply to the created mount unit
only regardless whether x-systemd.automount has been
specified.
Added in version 233.
x-systemd.wanted-by=, x-systemd.required-by=
In the created mount unit, configures a WantedBy= or
RequiredBy= dependency on another unit. This option may be
specified more than once. If this is specified, the default
dependencies (see above) other than umount.target on the
created mount unit, e.g. local-fs.target, are not
automatically created. Hence it is likely that some ordering
dependencies need to be set up manually through
x-systemd.before= and x-systemd.after=. See WantedBy= and
RequiredBy= in systemd.unit(5) for details.
Added in version 245.
x-systemd.wants-mounts-for=, x-systemd.requires-mounts-for=
Configures a RequiresMountsFor= or WantsMountsFor= dependency
between the created mount unit and other mount units. The
argument must be an absolute path. This option may be
specified more than once. See RequiresMountsFor= or
WantsMountsFor= in systemd.unit(5) for details.
Added in version 220.
x-systemd.graceful-option=
Additional mount option that shall be appended if supported by
the kernel. This may be used to configure mount options that
are optional and only enabled on kernels that support them.
Note that this is supported only for native kernel mount
options (i.e. explicitly not for mount options implemented in
userspace, such as those processed by /usr/bin/mount itself,
by FUSE or by mount helpers such as mount.nfs). This option
may be specified more than once.
Added in version 258.
x-systemd.device-bound=
Takes a boolean argument. If true or no argument, a BindsTo=
dependency on the backing device is set. If false, the mount
unit is not stopped no matter whether the backing device is
still present. This is useful when the file system is backed
by volume managers. If not set, and the mount comes from unit
fragments, i.e. generated from /etc/fstab by
systemd-fstab-generator(8) or loaded from a manually
configured mount unit, a combination of Requires= and
StopPropagatedFrom= dependencies is set on the backing device,
otherwise only Requires= is used.
Added in version 233.
x-systemd.automount
An automount unit will be created for the file system. See
systemd.automount(5) for details.
Added in version 215.
x-systemd.idle-timeout=
Configures the idle timeout of the automount unit. See
TimeoutIdleSec= in systemd.automount(5) for details.
Added in version 220.
x-systemd.device-timeout=
Configure how long systemd should wait for a device to show up
before giving up on an entry from /etc/fstab. Specify a time
in seconds or explicitly append a unit such as "s", "min",
"h", "ms".
Note that this option can only be used in /etc/fstab, and will
be ignored when part of the Options= setting in a unit file.
Added in version 215.
x-systemd.mount-timeout=
Configure how long systemd should wait for the mount command
to finish before giving up on an entry from /etc/fstab.
Specify a time in seconds or explicitly append a unit such as
"s", "min", "h", "ms".
Note that this option can only be used in /etc/fstab, and will
be ignored when part of the Options= setting in a unit file.
See TimeoutSec= below for details.
Added in version 233.
x-systemd.makefs
The file system will be initialized on the device. If the
device is not "empty", i.e. it contains any signature, the
operation will be skipped. It is hence expected that this
option remains set even after the device has been initialized.
Note that this option can only be used in /etc/fstab, and will
be ignored when part of the Options= setting in a unit file.
See [email protected](8).
wipefs(8) may be used to remove any signatures from a block
device to force x-systemd.makefs to reinitialize the device.
Added in version 236.
x-systemd.growfs
The file system will be grown to occupy the full block device.
If the file system is already at maximum size, no action will
be performed. It is hence expected that this option remains
set even after the file system has been grown. Only certain
file system types are supported, see
[email protected](8) for details.
Note that this option can only be used in /etc/fstab, and will
be ignored when part of the Options= setting in a unit file.
Added in version 236.
x-systemd.pcrfs
Measures file system identity information (mount point, type,
label, UUID, partition label, partition UUID) into PCR 15
after the file system has been mounted. This ensures the
[email protected](8) or systemd-pcrfs-root.service
services are pulled in by the mount unit.
Note that this option can only be used in /etc/fstab, and will
be ignored when part of the Options= setting in a unit file.
It is also implied for the root and /usr/ partitions
discovered by systemd-gpt-auto-generator(8).
Added in version 253.
x-systemd.validatefs
Validates mount constraint metadata of the mounted file system
after mounting it. This ensures the
[email protected](8) service is pulled in by the
mount unit.
Note that this option can only be used in /etc/fstab, and will
be ignored when part of the Options= setting in a unit file.
It is also implied for all partitions discovered by
systemd-gpt-auto-generator(8).
Added in version 258.
x-systemd.rw-only
If a mount operation fails to mount the file system
read-write, it normally tries mounting the file system
read-only instead. This option disables that behaviour, and
causes the mount to fail immediately instead. This option is
translated into the ReadWriteOnly= setting in a unit file.
Added in version 246.
_netdev
Normally the file system type is used to determine if a mount
is a "network mount", i.e. if it should only be started after
the network is available. Using this option overrides this
detection and specifies that the mount requires network.
Network mount units are ordered between remote-fs-pre.target
and remote-fs.target, instead of local-fs-pre.target and
local-fs.target. They also pull in network-online.target and
are ordered after it and network.target.
Added in version 235.
noauto, auto
With noauto, the mount unit will not be added as a dependency
for local-fs.target or remote-fs.target. This means that it
will not be mounted automatically during boot, unless it is
pulled in by some other unit. The auto option has the opposite
meaning and is the default.
Note that if x-systemd.automount (see above) is used, neither
auto nor noauto have any effect. The matching automount unit
will be added as a dependency to the appropriate target.
Added in version 215.
nofail
With nofail, this mount will be only wanted, not required, by
local-fs.target or remote-fs.target. Moreover, the mount unit
is not ordered before these target units. This means that the
boot will continue without waiting for the mount unit and
regardless whether the mount point can be mounted
successfully.
Added in version 215.
x-initrd.mount
An additional filesystem to be mounted in the initrd. See
initrd-fs.target description in systemd.special(7). This is
both an indicator to the initrd to mount this partition early
and an indicator to the host to leave the partition mounted
until final shutdown. Or in other words, if this flag is set
it is assumed the mount shall be active during the entire
regular runtime of the system, i.e. established before the
initrd transitions into the host all the way until the host
transitions to the final shutdown phase.
Added in version 215.
If a mount point is configured in both /etc/fstab and a unit file
that is stored below /usr/, the former will take precedence. If
the unit file is stored below /etc/, it will take precedence. This
means: native unit files take precedence over traditional
configuration files, but this is superseded by the rule that
configuration in /etc/ will always take precedence over
configuration in /usr/.
Mount unit files may include [Unit] and [Install] sections, which
are described in systemd.unit(5).
Mount unit files must include a [Mount] section, which carries
information about the file system mount points it supervises. A
number of options that may be used in this section are shared with
other unit types. These options are documented in systemd.exec(5),
systemd.kill(5) and systemd.resource-control(5). The options
specific to the [Mount] section of mount units are the following:
What=
Takes an absolute path or a fstab-style identifier of a device
node, file or other resource to mount. See mount(8) for
details. If this refers to a device node, a dependency on the
respective device unit is automatically created. (See
systemd.device(5) for more information.) This option is
mandatory. Note that the usual specifier expansion is applied
to this setting, literal percent characters should hence be
written as "%%". If this mount is a bind mount and the
specified path does not exist yet it is created as directory.
Where=
Takes an absolute path of a file or directory for the mount
point; in particular, the destination cannot be a symbolic
link. If the mount point does not exist at the time of
mounting, it is created as either a directory or a file. The
former is the usual case; the latter is done only if this
mount is a bind mount and the source (What=) is not a
directory. This string must be reflected in the unit filename.
(See above.) This option is mandatory.
Type=
Takes a string for the file system type. See mount(8) for
details. This setting is optional.
If the type is "overlay", and "upperdir=" or "workdir=" are
specified as options and the directories do not exist, they
will be created.
Options=
Mount options to use when mounting. This takes a
comma-separated list of options. This setting is optional.
Note that the usual specifier expansion is applied to this
setting, literal percent characters should hence be written as
"%%".
SloppyOptions=
Takes a boolean argument. If true, parsing of the options
specified in Options= is relaxed, and unknown mount options
are tolerated. This corresponds with mount(8)'s -s switch.
Defaults to off.
Added in version 215.
LazyUnmount=
Takes a boolean argument. If true, detach the filesystem from
the filesystem hierarchy at time of the unmount operation, and
clean up all references to the filesystem as soon as they are
not busy anymore. This corresponds with umount(8)'s -l switch.
Defaults to off.
Added in version 232.
ReadWriteOnly=
Takes a boolean argument. If false, a mount point that shall
be mounted read-write but cannot be mounted so is retried to
be mounted read-only. If true the operation will fail
immediately after the read-write mount attempt did not
succeed. This corresponds with mount(8)'s -w switch. Defaults
to off.
Added in version 246.
ForceUnmount=
Takes a boolean argument. If true, force an unmount (in case
of an unreachable NFS system). This corresponds with
umount(8)'s -f switch. Defaults to off.
Added in version 232.
DirectoryMode=
Directories of mount points (and any parent directories) are
automatically created if needed. This option specifies the
file system access mode used when creating these directories.
Takes an access mode in octal notation. Defaults to 0755.
TimeoutSec=
Configures the time to wait for the mount command to finish.
If a command does not exit within the configured time, the
mount will be considered failed and be shut down again. All
commands still running will be terminated forcibly via
SIGTERM, and after another delay of this time with SIGKILL.
(See KillMode= in systemd.kill(5).) Takes a unit-less value in
seconds, or a time span value such as "5min 20s". Pass 0 to
disable the timeout logic. The default value is set from
DefaultTimeoutStartSec= option in systemd-system.conf(5).
Check systemd.unit(5), systemd.exec(5), and systemd.kill(5) for
more settings.
systemd(1), systemctl(1), systemd-system.conf(5), systemd.unit(5),
systemd.exec(5), systemd.kill(5), systemd.resource-control(5),
systemd.service(5), systemd.device(5), proc(5), mount(8),
systemd-fstab-generator(8), systemd.directives(7),
systemd-mount(1)
1. API File Systems
https://systemd.io/API_FILE_SYSTEMS
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 258~rc2 SYSTEMD.MOUNT(5)
Pages that refer to this page: systemd(1), systemd-mount(1), crypttab(5), integritytab(5), systemd.automount(5), systemd.exec(5), systemd.kill(5), systemd.resource-control(5), systemd.swap(5), systemd-system.conf(5), systemd.unit(5), veritytab(5), systemd.directives(7), systemd.index(7), systemd.syntax(7), systemd-fstab-generator(8), systemd-gpt-auto-generator(8), [email protected](8)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|