SYSTEMD.MOUNT(5) systemd.mount SYSTEMD.MOUNT(5)
NAME
systemd.mount - Mount unit configuration
SYNOPSIS
mount.mount
DESCRIPTION
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.
AUTOMATIC DEPENDENCIES
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 BindsTo= and
After= type dependencies on the device unit encapsulating the block
device (see below).
• 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).
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 nofail mount option is set.
• Network mount units automatically acquire After= dependencies on
remote-fs-pre.target, network.target and network-online.target, and
gain a Before= dependency on remote-fs.target unless nofail mount
option is set. Towards the latter a Wants= unit is added as well.
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 normal automatic dependencies on
the created mount unit, e.g., local-fs.target, are not
automatically created. See WantedBy= and RequiredBy= in
systemd.unit(5) for details.
x-systemd.requires-mounts-for=
Configures a RequiresMountsFor= 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= in systemd.unit(5) for details.
x-systemd.device-bound
The block device backed file system will be upgraded to BindsTo=
dependency. This option is only useful when mounting file systems
manually with mount(8) as the default dependency in this case is
Requires=. This option is already implied by entries in /etc/fstab
or by mount units.
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.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).
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/.
OPTIONS
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) and
systemd.kill(5). The options specific to the [Mount] section of mount
units are the following:
What=
Takes an absolute path 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.
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.
SEE ALSO
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)
NOTES
1. API File Systems
https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
systemd 252 SYSTEMD.MOUNT(5)
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