systemd-fstab-generator

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

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

SYNOPSIS
       /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 by the initial RAM disk
           (initrd) while fstab= is honored by both the main system and the
           initrd.

       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" and "tmpfs".

           Use "gpt-auto" to explicitly request automatic root file system
           discovery via systemd-gpt-auto-generator(8).

           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.

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

       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).

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

           Otherwise, this parameter defaults to the /usr/ entry found in
           /etc/fstab on the root filesystem.

           mount.usr= is honored by the initrd.

       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.

       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.

       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 as part of the initial RAM disk ("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.

       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.

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)

systemd 249                                         SYSTEMD-FSTAB-GENERATOR(8)