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).
