focal (5) systemd.preset.5.gz

Provided by: systemd_245.4-4ubuntu3.24_amd64 bug

NAME

       systemd.preset - Service enablement presets

SYNOPSIS

       /etc/systemd/system-preset/*.preset

       /run/systemd/system-preset/*.preset

       /lib/systemd/system-preset/*.preset

       /etc/systemd/user-preset/*.preset

       /run/systemd/user-preset/*.preset

       /usr/lib/systemd/user-preset/*.preset

DESCRIPTION

       Preset files may be used to encode policy which units shall be enabled by default and which ones shall be
       disabled. They are read by systemctl preset (for more information see systemctl(1)) which uses this
       information to enable or disable a unit according to preset policy.  systemctl preset is used by the post
       install scriptlets of RPM packages (or other OS package formats), to enable/disable specific units by
       default on package installation, enforcing distribution, spin or administrator preset policy. This allows
       choosing a certain set of units to be enabled/disabled even before installing the actual package.

       For more information on the preset logic please have a look at the Presets[1] document.

       It is not recommended to ship preset files within the respective software packages implementing the
       units, but rather centralize them in a distribution or spin default policy, which can be amended by
       administrator policy.

       If no preset files exist, systemctl preset will enable all units that are installed by default. If this
       is not desired and all units shall rather be disabled, it is necessary to ship a preset file with a
       single, catchall "disable *" line. (See example 1, below.)

PRESET FILE FORMAT

       The preset files contain a list of directives consisting of either the word "enable" or "disable"
       followed by a space and a unit name (possibly with shell style wildcards), separated by newlines. Empty
       lines and lines whose first non-whitespace character is "#" or ";" are ignored. Multiple instance names
       for unit templates may be specified as a space separated list at the end of the line instead of the
       customary position between "@" and the unit suffix.

       Presets must refer to the "real" unit file, and not to any aliases. See systemd.unit(5) for a description
       of unit aliasing.

       Two different directives are understood: "enable" may be used to enable units by default, "disable" to
       disable units by default.

       If multiple lines apply to a unit name, the first matching one takes precedence over all others.

       Each preset file shall be named in the style of <priority>-<policy-name>.preset. Files in /etc/ override
       files with the same name in /usr/lib/ and /run/. Files in /run/ override files with the same name in
       /lib/. Packages should install their preset files in /lib/. Files in /etc/ are reserved for the local
       administrator, who may use this logic to override the preset files installed by vendor packages. All
       preset files are sorted by their filename in lexicographic order, regardless of which of the directories
       they reside in. If multiple files specify the same unit name, the entry in the file with the
       lexicographically earliest name will be applied. It is recommended to prefix all filenames with a
       two-digit number and a dash, to simplify the ordering of the files.

       If the administrator wants to disable a preset file supplied by the vendor, the recommended way is to
       place a symlink to /dev/null in /etc/systemd/system-preset/ bearing the same filename.

EXAMPLES

       Example 1. Default to off

           # /lib/systemd/system-preset/99-default.preset

           disable *

       This disables all units. Due to the filename prefix "99-", it will be read last and hence can easily be
       overridden by spin or administrator preset policy.

       Example 2. Enable multiple template instances

           # /lib/systemd/system-preset/80-dirsrv.preset

           enable dirsrv@.service foo bar baz

       This enables all three of dirsrv@foo.service, dirsrv@bar.service and dirsrv@baz.service.

       Example 3. A GNOME spin

           # /lib/systemd/system-preset/50-gnome.preset

           enable gdm.service
           enable colord.service
           enable accounts-daemon.service
           enable avahi-daemon.*

       This enables the three mentioned units, plus all avahi-daemon regardless of which unit type. A file like
       this could be useful for inclusion in a GNOME spin of a distribution. It will ensure that the units
       necessary for GNOME are properly enabled as they are installed. It leaves all other units untouched, and
       subject to other (later) preset files, for example like the one from the first example above.

       Example 4. Administrator policy

           # /etc/systemd/system-preset/00-lennart.preset

           enable httpd.service
           enable sshd.service
           enable postfix.service
           disable *

       This enables three specific services and disables all others. This is useful for administrators to
       specifically select the units to enable, and disable all others. Due to the filename prefix "00-" it will
       be read early and override all other preset policy files.

SEE ALSO

       systemd(1), systemctl(1), systemd-delta(1)

NOTES

        1. Presets
           https://www.freedesktop.org/wiki/Software/systemd/Preset