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.
There were two things to fix:
- Boost started shipping libboost_python.so as libboost_python{Major}{Minor}
- Make sure that mapnik and boost link to the correct version of python.
As far as I can tell, the systemd snippet hasn't depended on groups
being initialized since 5d02c02a9bfd6912e4e0f700b1b35e76d1d6bd3f in
2015, when a `setfacl` call was removed.
environment.sessionVariables cannot refer to the values of env vars,
and as a result this has caused problems in a variety of scenarios.
One use for these is that they're injected into /etc/profile,
elewhere these are used to populate an 'envfile' for pam
(`pam 5 pam_env.conf`) which mentions use of HOME being
potentially problematic.
Anyway if the goal is to make things easier for users,
simply do the NIX_PATH modification as extraInit.
This fixes the annoying problems generated by the current approach
(#40165 and others) while hopefully serving the original goal.
One way to check if things are borked is to try:
$ sudo env | grep NIX_PATH
Which (before this change) prints NIX_PATH variable with
an unexpanded $HOME in the value.
-------
This does mean the following won't contain user channels for 'will':
$ sudo -u will nix-instantiate --eval -E builtins.nixPath
However AFAICT currently they won't be present either,
due to unescaped $HOME. Unsure if similar situation for other users
of sessionVariables (not sudo) work with current situation
(if they exist they will regress after this change AFAIK).
