Description of problem:

Munin-node starts after the network.target which doesn't guarantee that network interfaces are up. As a result, Munin-node is not always able to determine FQDN hostname at boot because Munin-node uses hostname()+gethostbyname() pair which requires either FQDN hostname to be present in /etc/hosts or working DNS server early at boot (which is definitely not the case when the network interfaces were not brought up yet).

This produces an inconsistent behaviour. Early at boot Munin determines non-FQDN hostname, but if munin-node service is later restarted manually it determines FQDN hostname.

Version-Release number of selected component (if applicable):
RHEL 7.3
munin-2.0.25-11.el7

How reproducible:
Always

Steps to Reproduce:
1. Make sure the system is using short (non-FQDN) hostname
2. Make sure that hostname entry is not present in /etc/hosts. For example, take a default /etc/hosts file with "127.0.0.1   localhost ..." entries only.
3. Reboot the system, then telnet to port 4949. You'll see that Munin advertises itself with (short) non-FQDN hostname.
4. Restart Munin node: systemctl restart munin-node.
   Telnet to port 4949 again. You'll see that now Munin advertises itself with FQDN hostname.


Additional info:

This can be remediated by adding FQDN hostname to /etc/hosts, but this is probably not a good idea.
Suggested fix is to change /lib/systemd/system/munin-node.service file to start munin-node after network-online.target instead of network-target:

-After=network.target
+After=network-online.target