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How could I know if my linux starts with systemd or whatever package?

jww
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Lucho
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6 Answers6

40

I know this is an old question, but since I was just asking myself the same question - here are my 2ct.

Best solution I came up with

ps --no-headers -o comm 1

This returns either systemd or init and appears reliable across Linux distributions and releases.

file /sbin/init would work, with help of pattern matching. Output of ps 1 does not appear helpful since on some Linux distributions it will print 'init' (the symlink) despite systemd being used.

Debian 8

$ ps 1
  PID TTY      STAT   TIME COMMAND
    1 ?        Ss     0:02 /sbin/init
$ file /sbin/init
/sbin/init: symbolic link to /lib/systemd/systemd

RHEL 7

$ ps 1
  PID TTY      STAT   TIME COMMAND
    1 ?        Ss     7:46 /usr/lib/systemd/systemd --switched-root --system --deserialize 21
$ file /sbin/init
/sbin/init: symbolic link to `../lib/systemd/systemd'

SLES 12

$ ps 1
  PID TTY      STAT   TIME COMMAND
    1 ?        Ss     0:24 /usr/lib/systemd/systemd --switched-root --system --deserialize 21
$ file /sbin/init
/sbin/init: symbolic link to `../usr/lib/systemd/systemd'

openSUSE 13.1

$ ps 1
  PID TTY      STAT   TIME COMMAND
    1 ?        Ss     0:33 /sbin/init showopts
$ /sbin/init: symbolic link to `../usr/lib/systemd/systemd'
sborsky
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  • THIS is the best answer! – iconoclast Aug 18 '20 at 18:01
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    So Microsoft is shipping Ubuntu as part of WSL 2. On it, the systemctl command isn't available, not DBus bindings of Systemd are available, but some of the solutions proposed here literally report "systemd". But even MS confirms it is not systemd they are using in their "Ubuntu". This solution actually reveals the difference. For WSL 2 Ubuntu it returns init, on real Ubuntu it returns "systemd". Thanks for the answer. – Maxim V. Pavlov Jan 08 '22 at 20:10
  • `ps --no-headers -o comm 1` doesn't work on embedded Linux builds using BusyBox as the executable implementation of `ps`. Here's the error: `ps: unrecognized option '--no-headers' BusyBox v1.31.1 (2022-08-04 07:12:02 UTC) multi-call binary. Usage: ps [-o COL1,COL2=HEADER` – Gabriel Staples Aug 04 '22 at 23:48
25

Check what process is running as PID 1. You can do this by running ps 1 and scrolling to the top. If you have some systemd thing running as PID 1, you have systemd running.

Alternatively, run systemctl to list running systemd units.

You might also want to check what /sbin/init is; file /sbin/init will tell you if it's a real executable or if it's a symbolic link to some other package's executable. On a systemd box, for example:

root@boxy / # file /sbin/init
/sbin/init: symbolic link to ../lib/systemd/systemd

For more information, check this out: https://en.wikipedia.org/wiki/Linux_startup_process

Another way of seeing exactly what you have on your system is typing man init and seeing which program's man page you end up on.

Captain Man
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ecube
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    An easier way to see what's running with pid 1 is `ps 1` (the number 1). – deltab Dec 26 '15 at 01:58
  • @deltab Thanks for clearing that up! I'll edit it into the answer. – ecube Dec 26 '15 at 02:28
  • Great guys(@deltab,@dma1324)!!! My `ps 1` shows `/sbin/init`, and my `file /sbin/init` shows a binary, so I think it's not systemd. Then I have tried to run the `systemctl` command and get the "command not found" error, so now I'm sure I have not systemd on my linux. – Lucho Dec 26 '15 at 08:19
10

The correct solution is to check the presence of /run/systemd/system directory.

[[ -d /run/systemd/system ]] && echo "using systemd"

This method is used by systemd's own library function sd_booted(): https://www.freedesktop.org/software/systemd/man/sd_booted.html

intgr
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    Using '-d' instead of '-x' would be a bit more accurate. Prevents potential confusion about an executable file vs a directory. – dbernard Mar 18 '22 at 12:37
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    Updated my answer to use `-d`. I originally intended to use `-e` but got the options mixed up. These shouldn't make any difference in practice. – intgr Mar 21 '22 at 12:12
  • I prefer this instead: `[ -d /run/systemd/system ] && echo "using systemd" || echo "NOT using systemd"` – Gabriel Staples Aug 04 '22 at 23:52
0

Best answer I found so far was to ask the package manager of your distro which package installed the /sbin/init file. For example, on debian-based, that would be 

dpkg -S /sbin/init

If /sbin/init doesn't exist on your system, you can look for what program as pid 1 instead with ps 1.

ychaouche
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0

Run systemd-notify --booted (or systemctl is-system-running --quiet) and check if it returns 0 or not.

From systemd-notify(1) man page:

   --booted
       Returns 0 if the system was booted up with systemd,
       non-zero otherwise. If this option is passed, no
       message is sent. This option is hence unrelated to
       the other options. For details about the semantics
       of this option, see sd_booted(3). An alternate way
       to check for this state is to call systemctl(1)
       with the is-system-running command. It will return
       "offline" if the system was not booted with
       systemd.
fumiyas
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-1

@Trevor-Boyd-Smith linked to this discussion on Unix Stackexchange based on which I would like to offer:

[[ `systemctl` =~ -\.mount ]] || { echo 'Systemd not found'; exit 1; }

This bash statement will either just execute or print the message and exit the running script.

Christopher Oezbek
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