Prior to this change a service failure would occur when this tmpfiles
service did not finish fast enough and receive a SIGTERM from systemd.
Additionally, `initrd-nixos-activation` is already ordered with
`After=initrd-switch-root.target`.
These daemons should not be stopped, as they're foundational to a
proper functioning of the system. When switching configurations, they
only need a restart instead of that stop/start cycle.
Helps the following situation:
- SSH in initrd is enabled
- NixOS is waiting for a password to be typed at the console (or
provided via cryptsetup-askpass)
- The user logs in via SSH, but instead of running cryptsetup-askpass,
they run "cryptsetup open" directly (because they don't know that
they need to use NixOS's cryptsetup-askpass script, or because they
want to use a non-trivial unlocking method that is not natively
supported by this module)
Currently, in the above situation, NixOS will keep waiting for a
password to be entered even though the device is already unlocked. If
a password is entered, it will print a confusing "already exists"
error and keep asking for the same password.
We can improve on this by simply checking if the device is already
unlocked in our read loop. In this case, we don't need to do anything
other than return from the function and continue booting.
Removing the splash param only causes plymouth to display console
output by default; it still runs. Systemd stage 1 respects this flag
due to unit conditions preventing plymouth from even running. So this
brings parity to scripted stage 1.
When using nixos-enter (and so also nixos-install) on a system with etc-overlay enabled,
he activation script gets called directly, and there is no systemd running.
This violates a couple of assumptions in the etc-overlay activation script which
assumed that it only ever ran when switching into a new generation and that
the very first /etc would always have been set up by the systemd initrd.
As more and more things are being moved into systemd components (initrd services,
mount units, tmpfiles, etc), I think that it is going to become increasingly
difficult to stay compatible with these tools, but at least for now there is
no real alternative and so we probably want to be able to install systems
with etc-overlay enabled.
