Having fixed the Google Compute Engine image build process's copying
of store paths in PR #24264, I ran `nixos-rebuild --upgrade switch`...
and the GCE image broke again, because it sets the NixOS configuration
option for the sysctl variable `kernel.yama.ptrace_scope` to
`mkDefault "1"`, i.e., with override priority 1000, and now the
`sysctl` module sets the same option to `mkDefault "0"` (this was
changed in commit 86721a5f78).
This patch raises the override priority of the Google Compute Engine
image configuration's definition of the Yama sysctl option to 500
(still lower than the priority of an unmodified option definition).
I have tested that this patch allows the Google Compute Engine image
to again build successfully for me.
In `nixos/modules/virtualisation/google-compute-image.nix`, copy store
paths with `rsync -a` rather than `cp -prd`, because `rsync` seems
better able to handle the hard-links that may be present in the store,
whereas `cp` may fail to copy them.
I have tested that the Google Compute Engine image builds successfully
for me with this patch, whereas it did not without this patch.
This is the same fix applied for Azure images in commit
097ef6e435.
Fixes #23973.
- most nixos user only require time synchronisation,
while ntpd implements a battery-included ntp server (1,215 LOCs of C-Code vs 64,302)
- timesyncd support ntp server per interface (if configured through dhcp for instance)
- timesyncd is already included in the systemd package, switching to it would
save a little disk space (1,5M)
Systemd upstream provides targets for networking. This also includes a target network-online.target.
In this PR I remove / replace most occurrences since some of them were even wrong and could delay startup.
Setting nixosVersion to something custom is useful for meaningful GRUB
menus and /nix/store paths, but actuallly changing it rebulids the
whole system path (because of `nixos-version` script and manual
pages). Also, changing it is not a particularly good idea because you
can then be differentitated from other NixOS users by a lot of
programs that read /etc/os-release.
This patch introduces an alternative option that does all you want
from nixosVersion, but rebuilds only the very top system level and
/etc while using your label in the names of system /nix/store paths,
GRUB and other boot loaders' menus, getty greetings and so on.
The issue was that grub was not building the default entry which would
leave systems unbootable. This can now be safely reverted as the default
entry is being built once again.
This reverts commit fd1fb0403c.
