Pretty useful for laptops. I use them with:
```
services.logind.lidSwitch = "suspend-then-hibernate";
environment.etc."systemd/sleep.conf".text = "HibernateDelaySec=8h";
```
systemd provides two sysctl snippets, 50-coredump.conf and
50-default.conf.
These enable:
- Loose reverse path filtering
- Source route filtering
- `fq_codel` as a packet scheduler (this helps to fight bufferbloat)
This also configures the kernel to pass coredumps to `systemd-coredump`.
These sysctl snippets can be found in `/etc/sysctl.d/50-*.conf`,
and overridden via `boot.kernel.sysctl`
(which will place the parameters in `/etc/sysctl.d/60-nixos.conf`.
Let's start using these, like other distros already do for quite some
time, and remove those duplicate `boot.kernel.sysctl` options we
previously did set.
In the case of rp_filter (which systemd would set to 2 (loose)), make
our overrides to "1" more explicit.
Somewhen between systemd v239 and v242 upstream decided to no longer run
a few system services with `DyanmicUser=1` but failed to provide a
migration path for all the state those services left behind.
For the case of systemd-timesync the state has to be moved from
/var/lib/private/systemd/timesync to /var/lib/systemd/timesync if
/var/lib/systemd/timesync is currently a symlink.
We only do this if the stateVersion is still below 19.09 to avoid
starting to have an ever growing activation script for (then) ancient
systemd migrations that are no longer required.
See https://github.com/systemd/systemd/issues/12131 for details about
the missing migration path and related discussion.
Right now it's not at all obvious that one can override this option
using `services.logind.extraConfig`; we might as well add an option
for `killUserProcesses` directly so it's clear and documented.
* journald: forward message to syslog by default if a syslog implementation is installed
* added a test to ensure rsyslog is receiving messages when expected
* added rsyslogd tests to release.nix
The default value for journald's Storage option is "auto", which
determines whether to log to /var/log/journal based on whether that
directory already exists. So NixOS has been unconditionally creating
that directory in activation scripts.
However, we can get the same behavior by configuring journald.conf to
set Storage to "persistent" instead. In that case, journald will create
the directory itself if necessary.
Previously, the activation script was responsible for ensuring that
/etc/machine-id exists. However, the only time it could not already
exist is during stage-2-init, not while switching configurations,
because one of the first things systemd does when starting up as PID 1
is to create this file. So I've moved the initialization to
stage-2-init.
Furthermore, since systemd will do the equivalent of
systemd-machine-id-setup if /etc/machine-id doesn't have valid contents,
we don't need to do that ourselves.
We _do_, however, want to ensure that the file at least exists, because
systemd also uses the non-existence of this file to guess that this is a
first-boot situation. In that case, systemd tries to create some
symlinks in /etc/systemd/system according to its presets, which it can't
do because we've already populated /etc according to the current NixOS
configuration.
This is not necessary for any other activation script snippets, so it's
okay to do it after stage-2-init runs the activation script. None of
them declare a dependency on the "systemd" snippet. Also, most of them
only create files or directories in ways that obviously don't need the
machine-id set.
