Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 94 insertions, 0 deletions

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+---
+title: Porting systemd To New Distributions
+category: Concepts
+layout: default
+SPDX-License-Identifier: LGPL-2.1-or-later
+---
+
+# Porting systemd To New Distributions
+
+## HOWTO
+
+You need to make the follow changes to adapt systemd to your
+distribution:
+
+1. Find the right configure parameters for:
+
+   * `-Dsysvinit-path=`
+   * `-Dsysvrcnd-path=`
+   * `-Drc-local=`
+   * `-Dloadkeys-path=`
+   * `-Dsetfont-path=`
+   * `-Dtty-gid=`
+   * `-Dntp-servers=`
+   * `-Ddns-servers=`
+   * `-Dsupport-url=`
+
+2. Try it out.
+
+   Play around (as an ordinary user) with
+   `/usr/lib/systemd/systemd --test --system` for a test run
+   of systemd without booting. This will read the unit files and
+   print the initial transaction it would execute during boot-up.
+   This will also inform you about ordering loops and suchlike.
+
+## Compilation options
+
+The default configuration does not enable any optimization or hardening
+options. This is suitable for development and testing, but not for end-user
+installations.
+
+For deployment, optimization (`-O2` or `-O3` compiler options), link time
+optimization (`-Db_lto=true` meson option), and hardening (e.g.
+`-D_FORTIFY_SOURCE=2`, `-fstack-protector-strong`, `-fstack-clash-protection`,
+`-fcf-protection`, `-pie` compiler options, and `-z relro`, `-z now`,
+`--as-needed` linker options) are recommended. The most appropriate set of
+options depends on the architecture and distribution specifics so no default is
+provided.
+
+## NTP Pool
+
+By default, systemd-timesyncd uses the Google Public NTP servers
+`time[1-4].google.com`, if no other NTP configuration is available.
+They serve time that uses a
+[leap second smear](https://developers.google.com/time/smear)
+and can be up to .5s off from servers that use stepped leap seconds.
+
+If you prefer to use leap second steps, please register your own
+vendor pool at ntp.org and make it the built-in default by
+passing `-Dntp-servers=` to meson. Registering vendor
+pools is [free](http://www.pool.ntp.org/en/vendors.html).
+
+Use `-Dntp-servers=` to direct systemd-timesyncd to different fallback
+NTP servers.
+
+## DNS Servers
+
+By default, systemd-resolved uses Cloudflare and Google Public DNS servers
+`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`
+as fallback, if no other DNS configuration is available.
+
+Use `-Ddns-servers=` to direct systemd-resolved to different fallback
+DNS servers.
+
+## PAM
+
+The default PAM config shipped by systemd is really bare bones.
+It does not include many modules your distro might want to enable
+to provide a more seamless experience. For example, limits set in
+`/etc/security/limits.conf` will not be read unless you load `pam_limits`.
+Make sure you add modules your distro expects from user services.
+
+Pass `-Dpamconfdir=no` to meson to avoid installing this file and
+instead install your own.
+
+## Contributing Upstream
+
+We generally no longer accept distribution-specific patches to
+systemd upstream. If you have to make changes to systemd's source code
+to make it work on your distribution, unless your code is generic
+enough to be generally useful, we are unlikely to merge it. Please
+always consider adopting the upstream defaults. If that is not
+possible, please maintain the relevant patches downstream.
+
+Thank you for understanding.