systemd-fstab-generator(8)

1SYSTEMD-FSTAB-GENERATOR(8)  systemd-fstab-generator SYSTEMD-FSTAB-GENERATOR(8)
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NAME

6       systemd-fstab-generator - Unit generator for /etc/fstab
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SYNOPSIS

9       /usr/lib/systemd/system-generators/systemd-fstab-generator
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DESCRIPTION

12       systemd-fstab-generator is a generator that translates /etc/fstab (see
13       fstab(5) for details) into native systemd units early at boot and when
14       configuration of the system manager is reloaded. This will instantiate
15       mount and swap units as necessary.
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17       The passno field is treated like a simple boolean, and the ordering
18       information is discarded. However, if the root file system is checked,
19       it is checked before all the other file systems.
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21       See systemd.mount(5) and systemd.swap(5) for more information about
22       special /etc/fstab mount options this generator understands.
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24       One special topic is handling of symbolic links. Historical init
25       implementations supported symlinks in /etc/fstab. Because mount units
26       will refuse mounts where the target is a symbolic link, this generator
27       will resolve any symlinks as far as possible when processing /etc/fstab
28       in order to enhance backwards compatibility. If a symlink target does
29       not exist at the time that this generator runs, it is assumed that the
30       symlink target is the final target of the mount.
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32       systemd-fstab-generator implements systemd.generator(7).
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KERNEL COMMAND LINE

35       systemd-fstab-generator understands the following kernel command line
36       parameters:
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38       fstab=, rd.fstab=
39           Takes a boolean argument. Defaults to "yes". If "no", causes the
40           generator to ignore any mounts or swap devices configured in
41           /etc/fstab.  rd.fstab= is honored only by the initial RAM disk
42           (initrd) while fstab= is honored by both the main system and the
43           initrd.
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45       root=
46           Configures the operating system's root filesystem to mount when
47           running in the initrd. This accepts a device node path (usually
48           /dev/disk/by-uuid/...  or /dev/disk/by-label/...  or similar), or
49           the special values "gpt-auto" and "tmpfs".
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51           Use "gpt-auto" to explicitly request automatic root file system
52           discovery via systemd-gpt-auto-generator(8).
53
54           Use "tmpfs" in order to mount a tmpfs(5) file system as root file
55           system of the OS. This is useful in combination with mount.usr=
56           (see below) in order to combine a volatile root file system with a
57           separate, immutable /usr/ file system. Also see systemd.volatile=
58           below.
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60       rootfstype=
61           Takes the root filesystem type that will be passed to the mount
62           command.  rootfstype= is honored by the initrd.
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64       rootflags=
65           Takes the root filesystem mount options to use.  rootflags= is
66           honored by the initrd.
67
68           Note that unlike most kernel command line options this setting does
69           not override settings made in configuration files (specifically:
70           the mount option string in /etc/fstab). See systemd-remount-
71           fs.service(8).
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73       mount.usr=
74           Takes the /usr/ filesystem to be mounted by the initrd. If
75           mount.usrfstype= or mount.usrflags= is set, then mount.usr= will
76           default to the value set in root=.
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78           Otherwise, this parameter defaults to the /usr/ entry found in
79           /etc/fstab on the root filesystem.
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81           mount.usr= is honored by the initrd.
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83       mount.usrfstype=
84           Takes the /usr/ filesystem type that will be passed to the mount
85           command. If mount.usr= or mount.usrflags= is set, then
86           mount.usrfstype= will default to the value set in rootfstype=.
87
88           Otherwise, this value will be read from the /usr/ entry in
89           /etc/fstab on the root filesystem.
90
91           mount.usrfstype= is honored by the initrd.
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93       mount.usrflags=
94           Takes the /usr/ filesystem mount options to use. If mount.usr= or
95           mount.usrfstype= is set, then mount.usrflags= will default to the
96           value set in rootflags=.
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98           Otherwise, this value will be read from the /usr/ entry in
99           /etc/fstab on the root filesystem.
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101           mount.usrflags= is honored by the initrd.
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103       systemd.volatile=
104           Controls whether the system shall boot up in volatile mode. Takes a
105           boolean argument or the special value state.
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107           If false (the default), this generator makes no changes to the
108           mount tree and the system is booted up in normal mode.
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110           If true the generator ensures systemd-volatile-root.service(8) is
111           run as part of the initial RAM disk ("initrd"). This service
112           changes the mount table before transitioning to the host system, so
113           that a volatile memory file system ("tmpfs") is used as root
114           directory, with only /usr/ mounted into it from the configured root
115           file system, in read-only mode. This way the system operates in
116           fully stateless mode, with all configuration and state reset at
117           boot and lost at shutdown, as /etc/ and /var/ will be served from
118           the (initially unpopulated) volatile memory file system.
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120           If set to state the generator will leave the root directory mount
121           point unaltered, however will mount a "tmpfs" file system to /var/.
122           In this mode the normal system configuration (i.e. the contents of
123           "/etc/") is in effect (and may be modified during system runtime),
124           however the system state (i.e. the contents of "/var/") is reset at
125           boot and lost at shutdown.
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127           If this setting is set to "overlay" the root file system is set up
128           as "overlayfs" mount combining the read-only root directory with a
129           writable "tmpfs", so that no modifications are made to disk, but
130           the file system may be modified nonetheless with all changes being
131           lost at reboot.
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133           Note that in none of these modes the root directory, /etc/, /var/
134           or any other resources stored in the root file system are
135           physically removed. It's thus safe to boot a system that is
136           normally operated in non-volatile mode temporarily into volatile
137           mode, without losing data.
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139           Note that with the exception of "overlay" mode, enabling this
140           setting will only work correctly on operating systems that can boot
141           up with only /usr/ mounted, and are able to automatically populate
142           /etc/, and also /var/ in case of "systemd.volatile=yes".
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144           Also see root=tmpfs above, for a method to combine a "tmpfs" file
145           system with a regular /usr/ file system (as configured via
146           mount.usr=). The main distinction between systemd.volatile=yes, and
147           root=tmpfs in combination mount.usr= is that the former operates on
148           top of a regular root file system and temporarily obstructs the
149           files and directories above its /usr/ subdirectory, while the
150           latter does not hide any files, but simply mounts a unpopulated
151           tmpfs as root file system and combines it with a user picked /usr/
152           file system.
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154       systemd.swap
155           Takes a boolean argument or enables the option if specified without
156           an argument. If disabled, causes the generator to ignore any swap
157           devices configured in /etc/fstab. Defaults to enabled.
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NAME

SYNOPSIS

DESCRIPTION

KERNEL COMMAND LINE

SEE ALSO