How to make CFEngine recognize if systemd is used in Debian

CFEngine 3.6 tries to understand if a Linux is using systemd as init system by looking at the contents of /proc/1/cmdline, that happens in bundle common inventory_linux. That’s indeed a smart thing to do but unfortunately fails on Debian Jessie, where you have:

root@cf-test-v10:~# ls -l /sbin/init
lrwxrwxrwx 1 root root 20 May 26 06:07 /sbin/init -> /lib/systemd/systemd

the pseudo-file in /proc will still report /sbin/init and as a result the systemd class won’t be set. This affects services promises negatively and therefore I needed to make our policies try to outsmart the inventory 😉 These promises, added in a bundle of ours, did the trick:

bundle common debian_info {
  vars:
    init_is_link::
      "init_link_destination"
          string => filestat("/sbin/init","linktarget") ;

  classes:
    init_is_link::
      "systemd"
          expression => regcmp("/lib/systemd/systemd",
                               "$(init_link_destination)"),
          comment => "Check if /sbin/init links to systemd" ;

    debian::
      "init_is_link"
          expression => islink("/sbin/init"),
          comment => "Detect if init is a link" ;
}

Notice that our bundle is actually bigger, I cut off all the promises that were not relevant for this post. Enjoy!

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