docs/DISTRO_PORTING.md

   1 # Porting systemd To New Distributions
   2
   3 ## HOWTO
   4
   5 You need to make the follow changes to adapt systemd to your
   6 distribution:
   7
   8 1. Find the right configure parameters for:
   9
  10    * `-Drootprefix=`
  11    * `-Dsysvinit-path=`
  12    * `-Dsysvrcnd-path=`
  13    * `-Drc-local=`
  14    * `-Dhalt-local=`
  15    * `-Dloadkeys-path=`
  16    * `-Dsetfont-path=`
  17    * `-Dtty-gid=`
  18    * `-Dntp-servers=`
  19    * `-Ddns-servers=`
  20    * `-Dsupport-url=`
  21
  22 2. Try it out.
  23
  24    Play around (as an ordinary user) with
  25    `/usr/lib/systemd/systemd --test --system` for a test run
  26    of systemd without booting. This will read the unit files and
  27    print the initial transaction it would execute during boot-up.
  28    This will also inform you about ordering loops and suchlike.
  29
  30 ## NTP Pool
  31
  32 By default, systemd-timesyncd uses the Google Public NTP servers
  33 `time[1-4].google.com`, if no other NTP configuration is available.
  34 They serve time that uses a
  35 [leap second smear](https://developers.google.com/time/smear)
  36 and can be up to .5s off from servers that use stepped leap seconds.
  37
  38 If you prefer to use leap second steps, please register your own
  39 vendor pool at ntp.org and make it the built-in default by
  40 passing `-Dntp-servers=` to meson. Registering vendor
  41 pools is [free](http://www.pool.ntp.org/en/vendors.html).
  42
  43 Use `-Dntp-servers=` to direct systemd-timesyncd to different fallback
  44 NTP servers.
  45
  46 ## DNS Servers
  47
  48 By default, systemd-resolved uses the Google Public DNS servers
  49 `8.8.8.8`, `8.8.4.4`, `2001:4860:4860::8888`, `2001:4860:4860::8844`
  50 as fallback, if no other DNS configuration is available.
  51
  52 Use `-Ddns-servers=` to direct systemd-resolved to different fallback
  53 DNS servers.
  54
  55 ## PAM
  56
  57 The default PAM config shipped by systemd is really bare bones.
  58 It does not include many modules your distro might want to enable
  59 to provide a more seamless experience. For example, limits set in
  60 `/etc/security/limits.conf` will not be read unless you load `pam_limits`.
  61 Make sure you add modules your distro expects from user services.
  62
  63 Pass `-Dpamconfdir=no` to meson to avoid installing this file and
  64 instead install your own.
  65
  66 ## Contributing Upstream
  67
  68 We generally do no longer accept distribution-specific patches to
  69 systemd upstream. If you have to make changes to systemd's source code
  70 to make it work on your distribution, unless your code is generic
  71 enough to be generally useful, we are unlikely to merge it. Please
  72 always consider adopting the upstream defaults. If that is not
  73 possible, please maintain the relevant patches downstream.
  74
  75 Thank you for understanding.