117

I have come across a .service that contains the following:

[Install]
WantedBy=multi-user.target

The original .service file can be found here.

What is the the meaning of multi-user.target?

I am on Ubuntu 16.04 LTS.

4
  • 3
    Possible duplicate of What is systemd's target, service and socket?
    – muru
    Nov 15, 2017 at 8:49
  • 2
    It's not a proper duplicate, as (reading beyond the title) this question is asking about the [Install] section of a unit file. Ironically, it is the very next table down from the one hyperlinked in the question.
    – JdeBP
    Nov 15, 2017 at 11:52
  • 1
    This new related question has a lot more details in the answer and is very well worth reading.
    – Wildcard
    Mar 14, 2019 at 23:13
  • It really is, thanks for pointing there @Wildcard.
    – Rapti
    Jan 22, 2021 at 15:43

4 Answers 4

85

multi-user.target means that the systemd-service will start when the system reach runlevel 2.

To complement the answer, here's a table of the targets and their run levels:

Run Lvl Target Units                        Description
0       runlevel0.target, poweroff.target   Shut down and power off
1       runlevel1.target, rescue.target     Set up a rescue shell
2,3,4   runlevel[234].target,               Set up a non-gfx multi-user shell
        multi-user.target
5       runlevel5.target, graphical.target  Set up a gfx multi-user shell
6       runlevel6.target, reboot.target     Shut down and reboot the system
5
  • 1
    But it's WantedBy=multi-user.target, so it just means the service will start and before runlevel 2 right ? not necessarily when system reaches runlevel 2, am I wrong ?
    – Tristan
    Dec 10, 2018 at 17:53
  • 3
    What's a gfx multi-user shell? Any reference? Oct 14, 2019 at 7:46
  • 1
    A gfx multi-user shell refer to a multi-user system with a GUI. Oct 15, 2019 at 14:44
  • 2
    @TobiasHolm You might not be completely right, I'm getting the same target (graphical.target) even on a GUI-less Debian server with systemctl get-default.
    – aderchox
    Nov 27, 2021 at 10:30
  • FYI, see also man systemd.special and man runlevel.
    – Kai
    Jan 17 at 8:32
29

This is the dependencies handling mechanism in Systemd. `multi-user.targe\t is the alternative for runlevel 3 in SystemV world.

That said, reaching multi-user.target includes starting the Confluent ZooKeeper service.

Probably that's what you need indeed.

2
  • 8
    pretty vague answer. amazed that it got the green tick. some people be like, knows a little, throws a brittle.
    – ino
    Aug 21, 2021 at 5:14
  • actually, it's pretty informative even for systemd disliking person - if one is not ready to grasp content, they shall start learning from scratch.
    – silpol
    Feb 26, 2023 at 8:46
27

I found this landoflinux.com tutorial the simplest to understand. You can run the following command yourself to see what's there:

$ ls -al /lib/systemd/system/runlevel*
lrwxrwxrwx. 1 root root 15 Apr 25 10:31 /lib/systemd/system/runlevel0.target -> poweroff.target
lrwxrwxrwx. 1 root root 13 Apr 25 10:31 /lib/systemd/system/runlevel1.target -> rescue.target
lrwxrwxrwx. 1 root root 17 Apr 25 10:31 /lib/systemd/system/runlevel2.target -> multi-user.target
lrwxrwxrwx. 1 root root 17 Apr 25 10:31 /lib/systemd/system/runlevel3.target -> multi-user.target
lrwxrwxrwx. 1 root root 17 Apr 25 10:31 /lib/systemd/system/runlevel4.target -> multi-user.target
lrwxrwxrwx. 1 root root 16 Apr 25 10:31 /lib/systemd/system/runlevel5.target -> graphical.target
lrwxrwxrwx. 1 root root 13 Apr 25 10:31 /lib/systemd/system/runlevel6.target -> reboot.target

But you should probably just read the linked question accepted answer about targets.

3

tldr if a service is wanted by multi-user.target, the service requires a number of services needed for a non-graphical multi-user session to be started (see the required services in the chart below).

$ man systemd.special
...
multi-user.target

    A special target unit for setting up a multi-user system (non-graphical). This is pulled in by graphical.target.

    Units that are needed for a multi-user system shall add Wants= dependencies for their unit to this unit during installation. This is best configured via WantedBy=multi-user.target in the unit's [Install] section.
...

the services required by the target can be found in the chart below:

                             cryptsetup-pre.target veritysetup-pre.target
                                                  |
(various low-level                                v
 API VFS mounts:             (various cryptsetup/veritysetup devices...)
 mqueue, configfs,                                |    |
 debugfs, ...)                                    v    |
 |                                  cryptsetup.target  |
 |  (various swap                                 |    |    remote-fs-pre.target
 |   devices...)                                  |    |     |        |
 |    |                                           |    |     |        v
 |    v                       local-fs-pre.target |    |     |  (network file systems)
 |  swap.target                       |           |    v     v                 |
 |    |                               v           |  remote-cryptsetup.target  |
 |    |  (various low-level  (various mounts and  |  remote-veritysetup.target |
 |    |   services: udevd,    fsck services...)   |             |              |
 |    |   tmpfiles, random            |           |             |    remote-fs.target
 |    |   seed, sysctl, ...)          v           |             |              |
 |    |      |                 local-fs.target    |             | _____________/
 |    |      |                        |           |             |/
 \____|______|_______________   ______|___________/             |
                             \ /                                |
                              v                                 |
                       sysinit.target                           |
                              |                                 |
       ______________________/|\_____________________           |
      /              |        |      |               \          |
      |              |        |      |               |          |
      v              v        |      v               |          |
 (various       (various      |  (various            |          |
  timers...)      paths...)   |   sockets...)        |          |
      |              |        |      |               |          |
      v              v        |      v               |          |
timers.target  paths.target   |  sockets.target      |          |
      |              |        |      |               v          |
      v              \_______ | _____/         rescue.service   |
                             \|/                     |          |
                              v                      v          |
                          basic.target         rescue.target    |
                              |                                 |
                      ________v____________________             |
                     /              |              \            |
                     |              |              |            |
                     v              v              v            |
                 display-    (various system   (various system  |
             manager.service     services        services)      |
                     |         required for        |            |
                     |        graphical UIs)       v            v
                     |              |            multi-user.target
emergency.service    |              |              |
        |            \_____________ | _____________/
        v                          \|/
emergency.target                    v
                              graphical.target

source

the list of dependencies can also be found with

$ systemctl list-dependencies multi-user.target

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