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This may have more to do with detecting operating systems, but I specifically need the init system currently in use on the system.

Fedora 15 now uses systemd, Ubuntu uses Upstart, while others use variations of System V.

I have an application that I am writing to be a cross-platform daemon. The init scripts are being dynamically generated based on parameters that can be passed in on configure.

What I'd like to do is only generate the script for the particular init system that they are using. This way the install script can be run reasonably without parameters as root and the daemon can be "installed" automagically.

This is what I've come up with:

  • Search for systemd, upstart, etc in /bin
  • Compare /proc/1/comm to the systemd, upstart, etc
  • Ask the user

What would be the best cross/platform way of doing this?

Kind of related, Can I depend on bash to be on the majority of *nix or is it distribution/OS dependent?

Target platforms:

  • Mac OS
  • Linux (all distributions)
  • BSD (all versions)
  • Solaris, Minix, and other *nix
share|improve this question
Just to add my two cents, bash isn't installed by default on FreeBSD. –  Chinmay Kanchi Aug 7 '11 at 3:27
@tjameson, did you find a more direct way? I'm looking for the same thing but the answers here are just directions, not direct answers. In particular 1) script locations to search and 2) detecting the init system in effect, in case there are multiple ones installed (bash was answered directly). –  naxa Nov 24 '13 at 11:13
@naxa - Short answer, no. Long answer, you can get pretty far with ps -p 1 -o command (prints the path to the current init). On Arch Linux and Fedora (IIRC), it's a symlink to the systemd binary (probably same on all systemd systems). On upstart, init --help will print usage information, and on my box, upstart is mentioned where it says who to email. On FreeBSD (sysV), this will return an error. There may be similar clues on other systems, but since asking this question, I've decided to just create them for all platforms and make separate packages for each one. –  tjameson Nov 24 '13 at 19:48
thanks great info! Hopping from that I've learned that sudo lsof -a -p 1 -d txt may give even more exact results. ps may print an arbitrary name, whereas with lsof you will get the real executable path. (See my question unix.stackexchange.com/questions/102453/… ) –  naxa Nov 24 '13 at 22:25
None of the answers or comments in the linked question are bash related. The solutions should be applicable to your case as well. –  Marco Feb 10 '14 at 20:20

10 Answers 10

up vote 9 down vote accepted

For the second question, the answer is no and you should have a look at Resources for portable shell programming.

As for the first part - first of all, you certainly have to be careful. I'd say perform several tests to make sure - because the fact that someone does have systemd (for ex.) installed, does not mean it is actually used as the default init. Also, looking at /proc/1/comm can be misleading, because some installations of various init programs can automatically make /sbin/init a symlink hardlink or even a renamed version of their main program.

Maybe the most useful thing could be to look at the init scripts type - because those are what you'll actually be creating, no matter what runs them.

As a side note, you might also have a look at OpenRC which aims to provide a structure of init scripts that is compatible with both Linux and BSD systems.

share|improve this answer
What do you mean by "look at the init scripts type"? Often different init systems put their scripts/files somewhere besides /etc/init, like systemd puts them in /etc/systemd. If I was to have my script grok these, it could take a little while. Oh, and thanks for the link BTW for portable shell programming. –  tjameson Aug 7 '11 at 0:23
I meant to say that some init implementations can be adjusted to make use of different init scripts' types and locations (like /etc/rc.d/ or /etc/init.d/). And you should properly adjust your program at installation time to utilize the structure that is used on the given system. –  rozcietrzewiacz Aug 7 '11 at 1:08
So, are you saying that there is no reliable way to detect the init system programmatically? Having the user pass in parameters is certainly safer, but if the user does not pass anything in, what would be the best way to guess? –  tjameson Aug 7 '11 at 1:27
I've no idea what will be the best way for your program - it all depends on what systems will the program end up running. I haven't used too many distributions, but I was trying to share my observations to help you. It is a tough piece of scripting you are about to try and I tried to give you some view on the field - you must come to the final answer yourself or wait for more hints. –  rozcietrzewiacz Aug 7 '11 at 1:40
Cool, thanks for all your help. You definitely have pointed me in the right direction. –  tjameson Aug 7 '11 at 1:47

Using processes

Looking at the output from a couple of ps commands that can detect the various versions of systemd & upstart could be crafted like so:


$ ps -eaf|grep [u]pstart
root       492     1  0 Jan02 ?        00:00:00 upstart-udev-bridge --daemon
root      1027     1  0 Jan02 ?        00:00:00 upstart-socket-bridge --daemon


$ ps -eaf|grep [s]ystemd
root         1     0  0 07:27 ?        00:00:03 /usr/lib/systemd/systemd --switched-root --system --deserialize 20
root       343     1  0 07:28 ?        00:00:03 /usr/lib/systemd/systemd-journald
root       367     1  0 07:28 ?        00:00:00 /usr/lib/systemd/systemd-udevd
root       607     1  0 07:28 ?        00:00:00 /usr/lib/systemd/systemd-logind
dbus       615     1  0 07:28 ?        00:00:13 /bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation

Paying attention to what the name of the process is that's PID #1 can also shed potential light on which init system is being used. On Fedora 19 (which uses systemd, for example:

root         1     0  0 07:27 ?        00:00:03 /usr/lib/systemd/systemd --switched-root --system --deserialize 20

Notice it isn't init. On Ubuntu with Upstart it's still /sbin/init.

$ ps -efa|grep init
root         1     0  0 Jan02 ?        00:00:03 /sbin/init

NOTE: But use this with a bit of caution. There isn't anything set in stone that says a particular init system being used on a given distro has to have systemd as the PID #1.

The filesystem

If you interrogate the init executable you can get some info from it as well. Simply parsing the --version output. For example:


$ sudo /sbin/init --version
init (upstart 1.5)
Copyright (C) 2012 Scott James Remnant, Canonical Ltd.

This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY


$ type init
init is /usr/sbin/init

NOTE: The fact that init is not in its standard location is a bit of a hint/tell. It's always located on sysvinit systems in /sbin/init.


$ type init
init is /sbin/init

Also this:

$ sudo init --version
init: invalid option -- -
Usage: init 0123456SsQqAaBbCcUu


So there doesn't appear to be anyone way to do it but you could formulate a suite of checks that would pinpoint which init system you're using with a fairly high degree of confidence.

share|improve this answer
How about: pgrep systemd >/dev/null && echo init system: systemd –  Marco Feb 10 '14 at 20:27
Thank you, this is exactly what I was looking for: some steps to take to try to determine the init system. –  cpburnz Feb 10 '14 at 20:30
The PID #1 doesn't necessarily be /usr/lib/systemd/systemd if systemd is used, it's a false assumption. On my system, for instance, PID #1 is /sbin/init (I use systemd). It is distribution dependent. –  Marco Feb 10 '14 at 20:32
@Marco - OK, thanks I'll take that out. –  slm Feb 10 '14 at 20:40
  1. This is what distro-specific packages are for. There is much more to installing software properly than just detecting the init system. Many distros use SysVinit but not all of them write their init scripts the same way. The proper way to solve this is to include all the different variants and then bundle it up using spec files with distro-specific dependency names for rpm distros, deb files for apt based systems, etc. Almost all distros have some sort of package specification you can write that includes dependencies, scripts, init scripts, etc. Don't re-invent the wheel here.

  2. No. Which brings us back to 1. If you need bash it should be a dependency. You can specify this check as part of your configure scripts, but it should also be in the package descriptions.

Edit: Use flags on your configure script such as --with upstart or --without sysvinit. Pick a sane default, then the scripts that package your software for other distros can choose to run this with other options.

share|improve this answer
Hmph, so it's looking like I can't have a 'one script to rule them all' solution. I've seen a lot of programs that use autoconf or similar to handle cross-platform stuff, but it doesn't seem like it's the right tool for my application. Is maintaining versions for each platform really the only reliable solution? –  tjameson Aug 7 '11 at 7:27
One installation script to rule them all is a BadIdea. It ends up failing more places than it works. Autoconf is good as far as it goes. Work hard on keeping your end of the software as generic as possible and include alternate init scripts in your package. Setup package specifications for several major distros. If your software is good you can get other people to help you out with getting it packaged for other systems. –  Caleb Aug 7 '11 at 7:34
@tjameson: I just realized I forgot the most important bit. This sort of thing is usually done with switches passed to the configure script. Each distro's build/package routines can call different switches, and your configure/make only has to know what switch it was passed, not detect all the possible software configurations. –  Caleb Aug 7 '11 at 7:38
@Caleb- Yeah, I already have that logic in there, but good catch. I was hoping for a way to sniff the init system to use an intelligent guess than a sane default. –  tjameson Aug 7 '11 at 7:40

I've stepped into this problem myself and decided to do some tests. I fully agree with the answer that one should package for each distro separately, but sometimes there are practical issues that prevent that (not least manpower).

So for those that want to "auto-detect" here's what I've found out on a limited set of distros (more below):

  • You can tell upstart from:

    [[ `/sbin/init --version` =~ upstart ]] && echo yes || echo no
  • You can tell systemd from:

    [[ `systemctl` =~ -\.mount ]] && echo yes || echo no
  • You can tell sys-v init from:

    [[ -f /etc/init.d/cron && ! -h /etc/init.d/cron ]] && echo yes

Here are my experiments with the following command line:

if [[ `/sbin/init --version` =~ upstart ]]; then echo using upstart;
elif [[ `systemctl` =~ -\.mount ]]; then echo using systemd;
elif [[ -f /etc/init.d/cron && ! -h /etc/init.d/cron ]]; then echo using sysv-init;
else echo cannot tell; fi

on ec2 instances (I'm including the us-east AMI id):

  • CentOS6.4 ami-52009e3b: using upstart
  • CentOS7 ami-96a818fe: using systemd
  • Debian 6 ami-80e915e9: using sysv-init
  • Debian 7.5 ami-2c886c44: using sysv-init
  • Debian 7.6 GCE container-vm: using sysv-init
  • RHEL 6.5 ami-8d756fe4: using upstart
  • SLES 11 ami-e8084981: using sysv-init
  • Ubuntu 10.04 ami-6b350a02: using upstart
  • Ubuntu 12.04 ami-b08b6cd8: using upstart
  • Ubuntu 14.04 ami-a427efcc: using upstart
  • AWS linux 2014.3.2 ami-7c807d14: using upstart
  • Fedora 19 ami-f525389c: using systemd
  • Fedora 20 ami-21362b48: using systemd

Phew. Just to be clear: I am not claiming that this is foolproof!, it almost certainly isn't. Also note that for convenience I use bash regexp matches, which are not available everywhere. The above is good enough for me right now :-) and I hope it helps others. However, if you find a distro where it fails, please let me know and I'll try to fix it if there's an EC2 AMI that reproduces the problem...

share|improve this answer

On Gentoo, take a look at pid 1:

root         1  0.0  0.0   4216   340 ?        Ss    2013   0:57 init [3]

If it is init, then the init system is OpenRC. If it is systemd, then the init system is systemd.

You can detect Gentoo with [ -f /etc/gentoo-release ].

Another method on Gentoo is to use profile-config show, which will show what default profile is in use. All of the profiles except the two ending in /systemd use the OpenRC init. Keep in mind, these are only representative of a default and it is possible that the user has taken steps to override that default and may not be indicative of the init manger actually in use.

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Dumb question, but how do I check for pid 1? –  Faheem Mitha Feb 28 '14 at 23:20

Sometimes it's as easy as using ls :

$ ls -l /sbin/init
lrwxrwxrwx 1 root root 20 juin  25 12:04 /sbin/init -> /lib/systemd/systemd

I guess if /sbin/init is not a symbolic link, you'll have to check further following suggestions in other answers.

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On debian /sbin/init is a symlink to your default init so

ls -l /sbin/init

will give you the info you're looking for.

$ ls -l /sbin/init 
lrwxrwxrwx 1 root root 20 nov 18 13:15 /sbin/init -> /lib/systemd/systemd
share|improve this answer
Not so. On Ubuntu 14.04 with Upstart, it's not a symlink. –  muru Dec 3 '14 at 7:49
Install another init system and check again. –  rmorelli74 Dec 3 '14 at 12:24
And which other init can I install on Ubuntu 14.04? –  muru Dec 3 '14 at 12:28
...why not sysv or systemd? –  rmorelli74 Dec 3 '14 at 12:31
Ubuntu 14.04 has exactly one provider of /sbin/init: packages.ubuntu.com/… –  muru Dec 3 '14 at 12:32

This is really easy for some init systems. For systemd:

test -d /run/systemd/system

for upstart:

initctl --version | grep -q upstart

for anything else, you can just assume based on the distro (launchd on OS X, sysvinit on Debian, OpenRC on Gentoo).

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Currently I am writing a cross-platform framework to build init rc scripts, Maybe this can help you, or you can help me to add new platforms.


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Don't know about other systems then debian/ ubuntu but I do test this with the plain old file command.

file /sbin/init

give this:

/sbin/init: symbolic link to 'upstart'

share|improve this answer
What system did you test it on? There's no such thing as Debian/Ubuntu and this does not work on Debian. Did you try it on Ubuntu? –  terdon Oct 7 '14 at 12:53
Sorry for this confusion, I mean Debian (wheezy) /or Ubuntu (14.10.). Output on debian: file /sbin/init /sbin/init: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, BuildID[sha1]=0x8c68a736c6a4e6fadf22d5ac9debf11e79c6bdcd, stripped means we use SYSV here. Output for ubuntu is shown in my answer. –  zzeroo Oct 8 '14 at 14:14
Exactly, so your solution seems to only work if one happens to be using upstart and Ubuntu. –  terdon Oct 8 '14 at 14:17
@terdon: On systems (RHEL, Fedora) running systemd, it returns "symbolic link to...systemd"; on systems (Ubuntu) running upstart it returns "symbolic link to upstart"; on systems (RHEL, Ubuntu, Debian) running SysV init it returns "executable". While that's hardly a comprehensive survey, and this method is clearly not 100% foolproof, it's clearly much closer to "works for at least the major distros" rather than "only upstart and Ubuntu"! –  psmears Oct 20 '14 at 21:46
@psmears if it also works for some systemd systems, that is indeed better (but not mentioned in this answer). I just tested on a Debian running sysvinit, and three Ubuntus (10.04,12.04 and 14.04, all running upstart) and file /sbin/init returned "executable" on all systems. It also returns the same on a CentOS 5.8, a SLES 10, an Ubuntu 8.04, basically every single system I can get my hands on. So, as far as I can tell it doesn't even work for upstart and Ubuntu. –  terdon Oct 21 '14 at 0:06

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