SYSTEMD-FSTAB-GENERATOR(8)systemd-fstab-generatorSYSTEMD-FSTAB-GENERATOR(8)NAMEsystemd-fstab-generator - Unit generator for /etc/fstab
SYNOPSIS
/lib/systemd/system-generators/systemd-fstab-generator
DESCRIPTIONsystemd-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 LINEsystemd-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=
Takes the root filesystem to mount in the initrd. root= is honored
by the initrd.
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.
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.
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 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".
SEE ALSOsystemd(1), fstab(5), systemd.mount(5), systemd.swap(5), systemd-
cryptsetup-generator(8), kernel-command-line(7)systemd 236SYSTEMD-FSTAB-GENERATOR(8)
