SYSTEMD-FSTAB-GENERATOR(8)  systemd-fstab-generator SYSTEMD-FSTAB-GENERATOR(8)

NAME
       systemd-fstab-generator - Unit generator for /etc/fstab

SYNOPSIS
       /usr/lib/systemd/system-generators/systemd-fstab-generator

DESCRIPTION
       systemd-fstab-generator is a generator that translates /etc/fstab (see
       fstab(5) for details) into native systemd units early at boot and when
       configuration of the system manager is reloaded. This will instantiate
       mount and swap units as necessary.

       The passno field is treated like a simple boolean, and the ordering
       information is discarded. However, if the root file system is checked,
       it is checked before all the other file systems.

       See systemd.mount(5) and systemd.swap(5) for more information about
       special /etc/fstab mount options this generator understands.

       One special topic is handling of symbolic links. Historical init
       implementations supported symlinks in /etc/fstab. Because mount units
       will refuse mounts where the target is a symbolic link, this generator
       will resolve any symlinks as far as possible when processing /etc/fstab
       in order to enhance backwards compatibility. If a symlink target does
       not exist at the time that this generator runs, it is assumed that the
       symlink target is the final target of the mount.

       systemd-fstab-generator implements systemd.generator(7).

KERNEL COMMAND LINE
       systemd-fstab-generator understands the following kernel command line
       parameters:

       fstab=, rd.fstab=
	   Takes a boolean argument. Defaults to "yes". If "no", causes the
	   generator to ignore any mounts or swap devices configured in
	   /etc/fstab.	rd.fstab= is honored only in the initrd, while fstab=
	   is honored by both the main system and the initrd.

	   Added in version 186.

       root=
	   Configures the operating system's root filesystem to mount when
	   running in the initrd. This accepts a device node path (usually
	   /dev/disk/by-uuid/...  or /dev/disk/by-label/...  or similar), or
	   the special values "gpt-auto", "gpt-auto-force", "dissect",
	   "dissect-force", "fstab", "fstab", and "off".

	   Set to "gpt-auto", "gpt-auto-force", "dissect", "dissect-force" to
	   explicitly request automatic root file system discovery,
	   implemented in systemd-gpt-auto-generator(8).

	   Use "fstab" to explicitly request automatic root file system
	   discovery via the initrd /etc/fstab rather than via kernel command
	   line.

	   Use "tmpfs" in order to mount a tmpfs(5) file system as root file
	   system of the OS. This is useful in combination with mount.usr=
	   (see below) in order to combine a volatile root file system with a
	   separate, immutable /usr/ file system. Also see systemd.volatile=
	   below.

	   Use "bind:..." to bind mount another directory as operating system
	   root filesystems (added in v258). Expects an absolute path name
	   referencing an existing directory within the initrd's file
	   hierarchy to boot into.

	   Set to "off" to turn off mounting of a root file system.

	   Note that further root= values may be supported, implemented in
	   additional packages.

	   Added in version 217.

       rootfstype=
	   Takes the root filesystem type that will be passed to the mount
	   command.  rootfstype= is honored by the initrd.

	   Added in version 217.

       rootflags=
	   Takes the root filesystem mount options to use.  rootflags= is
	   honored by the initrd.

	   Note that unlike most kernel command line options this setting does
	   not override settings made in configuration files (specifically:
	   the mount option string in /etc/fstab). See systemd-remount-
	   fs.service(8).

	   Added in version 217.

       mount.usr=
	   Takes the /usr/ filesystem to be mounted by the initrd. If
	   mount.usrfstype= or mount.usrflags= is set, then the mount
	   configured via mount.usr= will default to the the same value set in
	   root=.

	   Set to "dissect" to explicitly request automatic /usr/ file system
	   discovery, implemented in systemd-gpt-auto-generator(8).

	   Set to "off" to turn off mounting of a separate /usr/ file system.

	   mount.usr= is honored by the initrd.

	   Added in version 217.

       mount.usrfstype=
	   Takes the /usr/ filesystem type that will be passed to the mount
	   command. If mount.usr= or mount.usrflags= is set, then
	   mount.usrfstype= will default to the value set in rootfstype=.

	   Otherwise, this value will be read from the /usr/ entry in
	   /etc/fstab on the root filesystem.

	   mount.usrfstype= is honored by the initrd.

	   Added in version 217.

       mount.usrflags=
	   Takes the /usr/ filesystem mount options to use. If mount.usr= or
	   mount.usrfstype= is set, then mount.usrflags= will default to the
	   value set in rootflags=.

	   Otherwise, this value will be read from the /usr/ entry in
	   /etc/fstab on the root filesystem.

	   mount.usrflags= is honored by the initrd.

	   Added in version 217.

       roothash=, usrhash=
	   These options are primarily read by systemd-veritysetup-
	   generator(8). When set this indicates that the root file system (or
	   /usr/) shall be mounted from Verity volumes with the specified
	   hashes. If these kernel command line options are set the root (or
	   /usr/) file system is thus mounted from a device mapper volume
	   /dev/mapper/root (or /dev/mapper/usr).

	   Added in version 251.

       systemd.volatile=
	   Controls whether the system shall boot up in volatile mode. Takes a
	   boolean argument or the special value state.

	   If false (the default), this generator makes no changes to the
	   mount tree and the system is booted up in normal mode.

	   If true the generator ensures systemd-volatile-root.service(8) is
	   run in the initrd. This service changes the mount table before
	   transitioning to the host system, so that a volatile memory file
	   system ("tmpfs") is used as root directory, with only /usr/ mounted
	   into it from the configured root file system, in read-only mode.
	   This way the system operates in fully stateless mode, with all
	   configuration and state reset at boot and lost at shutdown, as
	   /etc/ and /var/ will be served from the (initially unpopulated)
	   volatile memory file system.

	   If set to state the generator will leave the root directory mount
	   point unaltered, however will mount a "tmpfs" file system to /var/.
	   In this mode the normal system configuration (i.e. the contents of
	   "/etc/") is in effect (and may be modified during system runtime),
	   however the system state (i.e. the contents of "/var/") is reset at
	   boot and lost at shutdown.

	   If this setting is set to "overlay" the root file system is set up
	   as "overlayfs" mount combining the read-only root directory with a
	   writable "tmpfs", so that no modifications are made to disk, but
	   the file system may be modified nonetheless with all changes being
	   lost at reboot.

	   Note that in none of these modes the root directory, /etc/, /var/
	   or any other resources stored in the root file system are
	   physically removed. It's thus safe to boot a system that is
	   normally operated in non-volatile mode temporarily into volatile
	   mode, without losing data.

	   Note that with the exception of "overlay" mode, enabling this
	   setting will only work correctly on operating systems that can boot
	   up with only /usr/ mounted, and are able to automatically populate
	   /etc/, and also /var/ in case of "systemd.volatile=yes".

	   Also see root=tmpfs above, for a method to combine a "tmpfs" file
	   system with a regular /usr/ file system (as configured via
	   mount.usr=). The main distinction between systemd.volatile=yes, and
	   root=tmpfs in combination mount.usr= is that the former operates on
	   top of a regular root file system and temporarily obstructs the
	   files and directories above its /usr/ subdirectory, while the
	   latter does not hide any files, but simply mounts a unpopulated
	   tmpfs as root file system and combines it with a user picked /usr/
	   file system.

	   Added in version 233.

       systemd.swap=
	   Takes a boolean argument or enables the option if specified without
	   an argument. If disabled, causes the generator to ignore any swap
	   devices configured in /etc/fstab. Defaults to enabled.

	   Added in version 246.

       systemd.mount-extra=WHAT:WHERE[:FSTYPE[:OPTIONS]],
       rd.systemd.mount-extra=WHAT:WHERE[:FSTYPE[:OPTIONS]]
	   Specifies the mount unit. Takes at least two and at most four
	   fields separated with a colon (":"). Each field is handled as the
	   corresponding fstab field. This option can be specified multiple
	   times.  rd.systemd.mount-extra= is honored only in the initrd,
	   while systemd.mount-extra= is honored by both the main system and
	   the initrd. In the initrd, the mount point (and also source path if
	   the mount is bind mount) specified in systemd.mount-extra= is
	   prefixed with /sysroot/.

	   Example:

	       systemd.mount-extra=/dev/sda1:/mount-point:ext4:rw,noatime

	   Added in version 254.

       systemd.swap-extra=WHAT[:OPTIONS], rd.systemd.swap-extra=WHAT[:OPTIONS]
	   Specifies the swap unit. Takes the block device to be used as a
	   swap device, and optionally takes mount options followed by a colon
	   (":"). This option can be specified multiple times.
	   rd.systemd.swap-extra= is honored only in the initrd, while
	   systemd.swap-extra= is honored by both the main system and the
	   initrd.

	   Example:

	       systemd.swap-extra=/dev/sda2:x-systemd.makefs

	   Added in version 254.

SYSTEM CREDENTIALS
       fstab.extra
	   This credential may contain addition mounts to establish, in the
	   same format as fstab(5), with one mount per line. It is read in
	   addition to /etc/fstab.

	   Added in version 254.

SEE ALSO
       systemd(1), fstab(5), systemd.mount(5), systemd.swap(5), systemd-
       cryptsetup-generator(8), systemd-gpt-auto-generator(8), kernel-command-
       line(7), Known Environment Variables[1]

NOTES
	1. Known Environment Variables
	   https://systemd.io/ENVIRONMENT/

systemd 258					    SYSTEMD-FSTAB-GENERATOR(8)