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.
The
systemd-mount(1) command
allows creating .mount and .automount units dynamically and
transiently from the command line.
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
systemd-quotacheck.service and quotaon.service
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).
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.
fstab¶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.
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.
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.
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.
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. If doesn't, only Requires= is used.
x-systemd.automount¶An automount unit will be created for the file system. See systemd.automount(5) for details.
x-systemd.idle-timeout=¶Configures the idle timeout of the
automount unit. See TimeoutIdleSec= in
systemd.automount(5)
for details.
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.
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.
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 systemd-makefs@.service(8).
wipefs(8)
may be used to remove any signatures from a block device to force
x-systemd.makefs to reinitialize the device.
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 systemd-makefs@.service(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.
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
systemd-pcrfs@.service(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).
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.
_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.
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.
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.
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.
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 they don't 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.
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.
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.
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.
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.