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 ## Compilation options
  35
  36 The default configuration does not enable any optimization or hardening
  37 options. This is suitable for development and testing, but not for end-user
  38 installations.
  39
  40 For deployment, optimization (`-O2` or `-O3` compiler options), link time
  41 optimization (`-Db_lto=true` meson option), and hardening (e.g.
  42 `-D_FORTIFY_SOURCE=2`, `-fstack-protector-strong`, `-fstack-clash-protection`,
  43 `-fcf-protection`, `-pie` compiler options, and `-z relro`, `-z now`,
  44 `--as-needed` linker options) are recommended. The most appropriate set of
  45 options depends on the architecture and distribution specifics so no default is
  46 provided.
  47
  48 ## NTP Pool
  49
  50 By default, systemd-timesyncd uses the Google Public NTP servers
  51 `time[1-4].google.com`, if no other NTP configuration is available.
  52 They serve time that uses a
  53 [leap second smear](https://developers.google.com/time/smear)
  54 and can be up to .5s off from servers that use stepped leap seconds.
  55
  56 If you prefer to use leap second steps, please register your own
  57 vendor pool at ntp.org and make it the built-in default by
  58 passing `-Dntp-servers=` to meson. Registering vendor
  59 pools is [free](http://www.pool.ntp.org/en/vendors.html).
  60
  61 Use `-Dntp-servers=` to direct systemd-timesyncd to different fallback
  62 NTP servers.
  63
  64 ## DNS Servers
  65
  66 By default, systemd-resolved uses Cloudflare and Google Public DNS servers
  67 `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`
  68 as fallback, if no other DNS configuration is available.
  69
  70 Use `-Ddns-servers=` to direct systemd-resolved to different fallback
  71 DNS servers.
  72
  73 ## PAM
  74
  75 The default PAM config shipped by systemd is really bare bones.
  76 It does not include many modules your distro might want to enable
  77 to provide a more seamless experience. For example, limits set in
  78 `/etc/security/limits.conf` will not be read unless you load `pam_limits`.
  79 Make sure you add modules your distro expects from user services.
  80
  81 Pass `-Dpamconfdir=no` to meson to avoid installing this file and
  82 instead install your own.
  83
  84 ## Contributing Upstream
  85
  86 We generally do no longer accept distribution-specific patches to
  87 systemd upstream. If you have to make changes to systemd's source code
  88 to make it work on your distribution, unless your code is generic
  89 enough to be generally useful, we are unlikely to merge it. Please
  90 always consider adopting the upstream defaults. If that is not
  91 possible, please maintain the relevant patches downstream.
  92
  93 Thank you for understanding.