1SYSTEMD-FSTAB-GENERATOR(8) systemd-fstab-generator SYSTEMD-FSTAB-GENERATOR(8)
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6 systemd-fstab-generator - Unit generator for /etc/fstab
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9 /usr/lib/systemd/system-generators/systemd-fstab-generator
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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.
16 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.
20 See systemd.mount(5) and systemd.swap(5) for more information about
22 special /etc/fstab mount options this generator understands.
23 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.
31 systemd-fstab-generator implements systemd.generator(7).
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35 systemd-fstab-generator understands the following kernel command line
36 parameters:
37 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.
44 root=
46 Takes the root filesystem to mount in the initrd. root= is honored
47 by the initrd.
48 rootfstype=
50 Takes the root filesystem type that will be passed to the mount
51 command. rootfstype= is honored by the initrd.
52 rootflags=
54 Takes the root filesystem mount options to use. rootflags= is
55 honored by the initrd.
56 mount.usr=
58 Takes the /usr filesystem to be mounted by the initrd. If
59 mount.usrfstype= or mount.usrflags= is set, then mount.usr= will
60 default to the value set in root=.
61 Otherwise, this parameter defaults to the /usr entry found in
63 /etc/fstab on the root filesystem.
64 mount.usr= is honored by the initrd.
66 mount.usrfstype=
68 Takes the /usr filesystem type that will be passed to the mount
69 command. If mount.usr= or mount.usrflags= is set, then
70 mount.usrfstype= will default to the value set in rootfstype=.
71 Otherwise, this value will be read from the /usr entry in
73 /etc/fstab on the root filesystem.
74 mount.usrfstype= is honored by the initrd.
76 mount.usrflags=
78 Takes the /usr filesystem mount options to use. If mount.usr= or
79 mount.usrfstype= is set, then mount.usrflags= will default to the
80 value set in rootflags=.
81 Otherwise, this value will be read from the /usr entry in
83 /etc/fstab on the root filesystem.
84 mount.usrflags= is honored by the initrd.
86 systemd.volatile=
88 Controls whether the system shall boot up in volatile mode. Takes a
89 boolean argument or the special value state.
90 If false (the default), this generator makes no changes to the
92 mount tree and the system is booted up in normal mode.
93 If true the generator ensures systemd-volatile-root.service(8) is
95 run as part of the initial RAM disk ("initrd"). This service
96 changes the mount table before transitioning to the host system, so
97 that a volatile memory file system ("tmpfs") is used as root
98 directory, with only /usr mounted into it from the configured root
99 file system, in read-only mode. This way the system operates in
100 fully stateless mode, with all configuration and state reset at
101 boot and lost at shutdown, as /etc and /var will be served from the
102 (initially unpopulated) volatile memory file system.
103 If set to state the generator will leave the root directory mount
105 point unaltered, however will mount a "tmpfs" file system to /var.
106 In this mode the normal system configuration (i.e. the contents of
107 "/etc") is in effect (and may be modified during system runtime),
108 however the system state (i.e. the contents of "/var") is reset at
109 boot and lost at shutdown.
110 If this setting is set to "overlay" the root file system is set up
112 as "overlayfs" mount combining the read-only root directory with a
113 writable "tmpfs", so that no modifications are made to disk, but
114 the file system may be modified nonetheless with all changes being
115 lost at reboot.
116 Note that in none of these modes the root directory, /etc, /var or
118 any other resources stored in the root file system are physically
119 removed. It's thus safe to boot a system that is normally operated
120 in non-volatile mode temporarily into volatile mode, without losing
121 data.
122 Note that with the exception of "overlay" mode, enabling this
124 setting will only work correctly on operating systems that can boot
125 up with only /usr mounted, and are able to automatically populate
126 /etc, and also /var in case of "systemd.volatile=yes".
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129 systemd(1), fstab(5), systemd.mount(5), systemd.swap(5), systemd-
130 cryptsetup-generator(8), kernel-command-line(7)
131systemd 243 SYSTEMD-FSTAB-GENERATOR(8)