docs/DISTRO_PORTING.md

   1 ---
   2 title: Porting systemd To New Distributions
   3 category: Concepts
   4 layout: default
   5 ---
   6
   7 # Porting systemd To New Distributions
   8
   9 ## HOWTO
  10
  11 You need to make the follow changes to adapt systemd to your
  12 distribution:
  13
  14 1. Find the right configure parameters for:
  15
  16    * `-Drootprefix=`
  17    * `-Dsysvinit-path=`
  18    * `-Dsysvrcnd-path=`
  19    * `-Drc-local=`
  20    * `-Dloadkeys-path=`
  21    * `-Dsetfont-path=`
  22    * `-Dtty-gid=`
  23    * `-Dntp-servers=`
  24    * `-Ddns-servers=`
  25    * `-Dsupport-url=`
  26
  27 2. Try it out.
  28
  29    Play around (as an ordinary user) with
  30    `/usr/lib/systemd/systemd --test --system` for a test run
  31    of systemd without booting. This will read the unit files and
  32    print the initial transaction it would execute during boot-up.
  33    This will also inform you about ordering loops and suchlike.
  34
  35 ## Compilation options
  36
  37 The default configuration does not enable any optimization or hardening
  38 options. This is suitable for development and testing, but not for end-user
  39 installations.
  40
  41 For deployment, optimization (`-O2` or `-O3` compiler options), link time
  42 optimization (`-Db_lto=true` meson option), and hardening (e.g.
  43 `-D_FORTIFY_SOURCE=2`, `-fstack-protector-strong`, `-fstack-clash-protection`,
  44 `-fcf-protection`, `-pie` compiler options, and `-z relro`, `-z now`,
  45 `--as-needed` linker options) are recommended. The most appropriate set of
  46 options depends on the architecture and distribution specifics so no default is
  47 provided.
  48
  49 ## NTP Pool
  50
  51 By default, systemd-timesyncd uses the Google Public NTP servers
  52 `time[1-4].google.com`, if no other NTP configuration is available.
  53 They serve time that uses a
  54 [leap second smear](https://developers.google.com/time/smear)
  55 and can be up to .5s off from servers that use stepped leap seconds.
  56
  57 If you prefer to use leap second steps, please register your own
  58 vendor pool at ntp.org and make it the built-in default by
  59 passing `-Dntp-servers=` to meson. Registering vendor
  60 pools is [free](http://www.pool.ntp.org/en/vendors.html).
  61
  62 Use `-Dntp-servers=` to direct systemd-timesyncd to different fallback
  63 NTP servers.
  64
  65 ## DNS Servers
  66
  67 By default, systemd-resolved uses Cloudflare and Google Public DNS servers
  68 `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`
  69 as fallback, if no other DNS configuration is available.
  70
  71 Use `-Ddns-servers=` to direct systemd-resolved to different fallback
  72 DNS servers.
  73
  74 ## PAM
  75
  76 The default PAM config shipped by systemd is really bare bones.
  77 It does not include many modules your distro might want to enable
  78 to provide a more seamless experience. For example, limits set in
  79 `/etc/security/limits.conf` will not be read unless you load `pam_limits`.
  80 Make sure you add modules your distro expects from user services.
  81
  82 Pass `-Dpamconfdir=no` to meson to avoid installing this file and
  83 instead install your own.
  84
  85 ## Contributing Upstream
  86
  87 We generally do no longer accept distribution-specific patches to
  88 systemd upstream. If you have to make changes to systemd's source code
  89 to make it work on your distribution, unless your code is generic
  90 enough to be generally useful, we are unlikely to merge it. Please
  91 always consider adopting the upstream defaults. If that is not
  92 possible, please maintain the relevant patches downstream.
  93
  94 Thank you for understanding.