Hi,
prometheus-alertmanager needs network (absolute minimum:
loopback), so at a minimum add this to the service unit
[Unit]
...
Wants=network.target
After=network.target
If one runs prometheus-alertmanager in a cluster (which
even is the default: it listens for cluster connections),
it needs even more networking with proper IPs being
assigned to interfaces. So I'd highly recommend this:
[Unit]
...
Wants=network.target
After=network.target network-online.target
One could even go for a Wants with network-online.target,
but I think, it's good enough this way: Other more
important services will likely have the needed Wants.
Cheers
Elrond