Setting this variable in the environment of systemd-timedated allows
'timedatectl' to tell if an NTP service is running.
Closes#48917.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
Most importantly, this sets PrivateTmp, ProtectHome, and ProtectSystem
so that Chrony flaws are mitigated, should they occur.
Moving to ProtectSystem=full however, requires moving the chrony key
files under /var/lib/chrony -- which should be fine, anyway.
This also ensures ConditionCapability=CAP_SYS_TIME is set, ensuring
that chronyd will only be launched in an environment where such a
capability can be granted.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
Peviously only the timesyncd systemd unit was disabled. This meant
that when you activate a system that has chronyd enabled the following
strange startup behaviour takes place:
systemd[1]: Starting chrony NTP daemon...
systemd[1]: Stopping Network Time Synchronization...
systemd[1]: Stopped chrony NTP daemon.
systemd[1]: Starting Network Time Synchronization...
This fixes an issue where `nixops deploy` wouldn't restart the chrony
service when the chrony configuration changed, because it wouldn't
detect that `/etc/chrony.conf` was a dependency of the chrony service.
- 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)
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
