You probably want to have some more persistent files than the two bind mounts
we already have created during the setup.
Adding persistent files from etc:
# machine-id is used by systemd for the journal, if
# you don't persist this file you won't be able to easily
# use journalctl to look at journals for previous boots.
# if you want to run an openssh daemon, you may want to
# store the host keys across reboots.
# For this to work you will need to create the
# directory yourself:
# $ mkdir /nix/persist/etc/ssh
From here you can probably figure out how to do more bind-mounts and
symbolic links in
/etc for the files you want to live across reboots.
A very useful tool to discovering files in your tmpfs is ncdu, I tend
to run sudo ncdu -x / to walk around the directory tree to see if there's
something I want to make persistent.
You may want to make your
/home persistent, that can be done by a mount
or bind-mount. I have that as tmpfs as well, but that is probably enough
content for it's own post.