1SYSTEMD.PRESET(5) systemd.preset SYSTEMD.PRESET(5)
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6 systemd.preset - Service enablement presets
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9 /etc/systemd/system-preset/*.preset
10 /run/systemd/system-preset/*.preset
12 /usr/lib/systemd/system-preset/*.preset
14 /etc/systemd/user-preset/*.preset
16 /run/systemd/user-preset/*.preset
18 /usr/lib/systemd/user-preset/*.preset
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22 Preset files may be used to encode policy which units shall be enabled
23 by default and which ones shall be disabled. They are read by systemctl
24 preset which uses this information to enable or disable a unit.
25 Depending on that policy, systemctl preset is identical to systemctl
26 enable or systemctl disable. systemctl preset is used by the post
27 install scriptlets of rpm packages (or other OS package formats), to
28 enable/disable specific units by default on package installation,
29 enforcing distribution, spin or administrator preset policy. This
30 allows choosing a certain set of units to be enabled/disabled even
31 before installing the actual package. For more information, see
32 systemctl(1).
33 It is not recommended to ship preset files within the respective
35 software packages implementing the units, but rather centralize them in
36 a distribution or spin default policy, which can be amended by
37 administrator policy, see below.
38 If no preset files exist, preset operations will enable all units that
40 are installed by default. If this is not desired and all units shall
41 rather be disabled, it is necessary to ship a preset file with a
42 single, catchall "disable *" line. (See example 1, below.)
43 When the machine is booted for the first time, systemd(1) will
45 enable/disable all units according to preset policy, similarly to
46 systemctl preset-all. Also see "First Boot Semantics" in machine-id(5).
47
49 The preset files contain a list of directives, one per line. Empty
50 lines and lines whose first non-whitespace character is "#" or ";" are
51 ignored. Each directive consists of one of the words "enable",
52 "disable", or "ignore", followed by whitespace and a unit name. The
53 unit name may contain shell-style wildcards.
54 For the enable directive for template units, one or more instance names
56 may be specified as a space-separated list after the unit name. In this
57 case, those instances will be enabled instead of the instance specified
58 via DefaultInstance= in the unit.
59 Presets must refer to the "real" unit file, and not to any aliases. See
61 systemd.unit(5) for a description of unit aliasing.
62 Three different directives are understood: "enable" may be used to
64 enable units by default, "disable" to disable units by default, and
65 "ignore" to ignore units and leave existing configuration intact.
66 If multiple lines apply to a unit name, the first matching one takes
68 precedence over all others.
69 Each preset file shall be named in the style of
71 <priority>-<policy-name>.preset. Files in /etc/ override files with the
72 same name in /usr/lib/ and /run/. Files in /run/ override files with
73 the same name in /usr/lib/. Packages should install their preset files
74 in /usr/lib/. Files in /etc/ are reserved for the local administrator,
75 who may use this logic to override the preset files installed by vendor
76 packages. All preset files are sorted by their filename in
77 lexicographic order, regardless of which of the directories they reside
78 in. If multiple files specify the same unit name, the entry in the file
79 with the lexicographically earliest name will be applied. It is
80 recommended to prefix all filenames with a two-digit number and a dash,
81 to simplify the ordering of the files.
82 If the administrator wants to disable a preset file supplied by the
84 vendor, the recommended way is to place a symlink to /dev/null in
85 /etc/systemd/system-preset/ bearing the same filename.
86
88 Example 1. Default to off
89 # /usr/lib/systemd/system-preset/99-default.preset
91 disable *
93 This disables all units. Due to the filename prefix "99-", it will be
95 read last and hence can easily be overridden by spin or administrator
96 preset policy.
97 Example 2. Enable multiple template instances
99 # /usr/lib/systemd/system-preset/80-dirsrv.preset
101 enable dirsrv@.service foo bar baz
103 This enables all three of dirsrv@foo.service, dirsrv@bar.service and
105 dirsrv@baz.service.
106 Example 3. A GNOME spin
108 # /usr/lib/systemd/system-preset/50-gnome.preset
110 enable gdm.service
112 enable colord.service
113 enable accounts-daemon.service
114 enable avahi-daemon.*
115 This enables the three mentioned units, plus all avahi-daemon
117 regardless of which unit type. A file like this could be useful for
118 inclusion in a GNOME spin of a distribution. It will ensure that the
119 units necessary for GNOME are properly enabled as they are installed.
120 It leaves all other units untouched, and subject to other (later)
121 preset files, for example like the one from the first example above.
122 Example 4. Administrator policy
124 # /etc/systemd/system-preset/00-lennart.preset
126 enable httpd.service
128 enable sshd.service
129 enable postfix.service
130 disable *
131 This enables three specific services and disables all others. This is
133 useful for administrators to specifically select the units to enable,
134 and disable all others. Due to the filename prefix "00-" it will be
135 read early and override all other preset policy files.
136
138 Different distributions have different policies on which services shall
139 be enabled by default when the package they are shipped in is
140 installed. On Fedora all services stay off by default, so that
141 installing a package will not cause a service to be enabled (with some
142 exceptions). On Debian all services are immediately enabled by default,
143 so that installing a package will cause its services to be enabled
144 right-away.
145 Even within a single distribution, different spins (flavours, remixes,
147 whatever you might want to call them) of a distribution also have
148 different policies on what services to enable, and what services to
149 leave off. For example, Fedora Workstation will enable gdm as display
150 manager by default, while the Fedora KDE spin will enable sddm instead.
151 Different sites might also have different policies what to turn on by
153 default and what to turn off. For example, one administrator would
154 prefer to enforce the policy of "sshd should be always on, but
155 everything else off", while another one might say "snmpd always on, and
156 for everything else use the distribution policy defaults".
157 Traditionally, policy about which services shall be enabled were
159 implemented in each package individually. This made it cumbersome to
160 implement different policies per spin or per site, or to create
161 software packages that do the right thing on more than one
162 distribution. The enablement mechanism was also encoding the enablement
163 policy.
164 The preset mechanism allows clean separation of the enablement
166 mechanism (inside the package scriptlets, by invoking systemctl preset)
167 and enablement policy (centralized in the preset files), and lifts the
168 configuration out of individual packages. Preset files may be written
169 for specific distributions, for specific spins or for specific sites,
170 in order to enforce different policies as needed. It is recommended to
171 apply the policy encoded in preset files in package installation
172 scriptlets.
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175 systemd(1), systemctl(1), systemd-delta(1)
176 daemon(7) has a discussion of packaging scriptlets.
178 Fedora page introducing the use of presets: Features/PackagePresets[1].
180
182 1. Features/PackagePresets
183 https://fedoraproject.org/wiki/Features/PackagePresets
184systemd 254 SYSTEMD.PRESET(5)