docs/DISTRO_PORTING.md

   1 ---
   2 title: Porting systemd To New Distributions
   3 ---
   4
   5 # Porting systemd To New Distributions
   6
   7 ## HOWTO
   8
   9 You need to make the follow changes to adapt systemd to your
  10 distribution:
  11
  12 1. Find the right configure parameters for:
  13
  14    * `-Drootprefix=`
  15    * `-Dsysvinit-path=`
  16    * `-Dsysvrcnd-path=`
  17    * `-Drc-local=`
  18    * `-Dhalt-local=`
  19    * `-Dloadkeys-path=`
  20    * `-Dsetfont-path=`
  21    * `-Dtty-gid=`
  22    * `-Dntp-servers=`
  23    * `-Ddns-servers=`
  24    * `-Dsupport-url=`
  25
  26 2. Try it out.
  27
  28    Play around (as an ordinary user) with
  29    `/usr/lib/systemd/systemd --test --system` for a test run
  30    of systemd without booting. This will read the unit files and
  31    print the initial transaction it would execute during boot-up.
  32    This will also inform you about ordering loops and suchlike.
  33
  34 ## NTP Pool
  35
  36 By default, systemd-timesyncd uses the Google Public NTP servers
  37 `time[1-4].google.com`, if no other NTP configuration is available.
  38 They serve time that uses a
  39 [leap second smear](https://developers.google.com/time/smear)
  40 and can be up to .5s off from servers that use stepped leap seconds.
  41
  42 If you prefer to use leap second steps, please register your own
  43 vendor pool at ntp.org and make it the built-in default by
  44 passing `-Dntp-servers=` to meson. Registering vendor
  45 pools is [free](http://www.pool.ntp.org/en/vendors.html).
  46
  47 Use `-Dntp-servers=` to direct systemd-timesyncd to different fallback
  48 NTP servers.
  49
  50 ## DNS Servers
  51
  52 By default, systemd-resolved uses Cloudflare and Google Public DNS servers
  53 `1.1.1.1`, `8.8.8.8`, `1.0.0.1`, `8.8.4.4`, `2606:4700:4700::1111`, `2001:4860:4860::8888`, `2606:4700:4700::1001`, `2001:4860:4860::8844`
  54 as fallback, if no other DNS configuration is available.
  55
  56 Use `-Ddns-servers=` to direct systemd-resolved to different fallback
  57 DNS servers.
  58
  59 ## PAM
  60
  61 The default PAM config shipped by systemd is really bare bones.
  62 It does not include many modules your distro might want to enable
  63 to provide a more seamless experience. For example, limits set in
  64 `/etc/security/limits.conf` will not be read unless you load `pam_limits`.
  65 Make sure you add modules your distro expects from user services.
  66
  67 Pass `-Dpamconfdir=no` to meson to avoid installing this file and
  68 instead install your own.
  69
  70 ## Contributing Upstream
  71
  72 We generally do no longer accept distribution-specific patches to
  73 systemd upstream. If you have to make changes to systemd's source code
  74 to make it work on your distribution, unless your code is generic
  75 enough to be generally useful, we are unlikely to merge it. Please
  76 always consider adopting the upstream defaults. If that is not
  77 possible, please maintain the relevant patches downstream.
  78
  79 Thank you for understanding.