1---
2title: Porting systemd To New Distributions
3category: Concepts
4layout: default
5SPDX-License-Identifier: LGPL-2.1-or-later
6---
7
8# Porting systemd To New Distributions
9
10## HOWTO
11
12You need to make the follow changes to adapt systemd to your
13distribution:
14
151. Find the right configure parameters for:
16
17   * `-Drootprefix=`
18   * `-Dsysvinit-path=`
19   * `-Dsysvrcnd-path=`
20   * `-Drc-local=`
21   * `-Dloadkeys-path=`
22   * `-Dsetfont-path=`
23   * `-Dtty-gid=`
24   * `-Dntp-servers=`
25   * `-Ddns-servers=`
26   * `-Dsupport-url=`
27
282. Try it out.
29
30   Play around (as an ordinary user) with
31   `/usr/lib/systemd/systemd --test --system` for a test run
32   of systemd without booting. This will read the unit files and
33   print the initial transaction it would execute during boot-up.
34   This will also inform you about ordering loops and suchlike.
35
36## Compilation options
37
38The default configuration does not enable any optimization or hardening
39options. This is suitable for development and testing, but not for end-user
40installations.
41
42For deployment, optimization (`-O2` or `-O3` compiler options), link time
43optimization (`-Db_lto=true` meson option), and hardening (e.g.
44`-D_FORTIFY_SOURCE=2`, `-fstack-protector-strong`, `-fstack-clash-protection`,
45`-fcf-protection`, `-pie` compiler options, and `-z relro`, `-z now`,
46`--as-needed` linker options) are recommended. The most appropriate set of
47options depends on the architecture and distribution specifics so no default is
48provided.
49
50## NTP Pool
51
52By default, systemd-timesyncd uses the Google Public NTP servers
53`time[1-4].google.com`, if no other NTP configuration is available.
54They serve time that uses a
55[leap second smear](https://developers.google.com/time/smear)
56and can be up to .5s off from servers that use stepped leap seconds.
57
58If you prefer to use leap second steps, please register your own
59vendor pool at ntp.org and make it the built-in default by
60passing `-Dntp-servers=` to meson. Registering vendor
61pools is [free](http://www.pool.ntp.org/en/vendors.html).
62
63Use `-Dntp-servers=` to direct systemd-timesyncd to different fallback
64NTP servers.
65
66## DNS Servers
67
68By default, systemd-resolved uses Cloudflare and Google Public DNS servers
69`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`
70as fallback, if no other DNS configuration is available.
71
72Use `-Ddns-servers=` to direct systemd-resolved to different fallback
73DNS servers.
74
75## PAM
76
77The default PAM config shipped by systemd is really bare bones.
78It does not include many modules your distro might want to enable
79to provide a more seamless experience. For example, limits set in
80`/etc/security/limits.conf` will not be read unless you load `pam_limits`.
81Make sure you add modules your distro expects from user services.
82
83Pass `-Dpamconfdir=no` to meson to avoid installing this file and
84instead install your own.
85
86## Contributing Upstream
87
88We generally do no longer accept distribution-specific patches to
89systemd upstream. If you have to make changes to systemd's source code
90to make it work on your distribution, unless your code is generic
91enough to be generally useful, we are unlikely to merge it. Please
92always consider adopting the upstream defaults. If that is not
93possible, please maintain the relevant patches downstream.
94
95Thank you for understanding.
96