Puppet » Facter

Linux supports naming interface aliases. Example here:

eth1      Lien encap:Ethernet  HWaddr CENSORED
          inet adr:192.168.0.42  Bcast:192.168.0.255  Masque:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:72056 errors:0 dropped:0 overruns:0 frame:0
          TX packets:43727 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:1000 
          RX bytes:6908277 (6.5 MiB)  TX bytes:96520716 (92.0 MiB)

eth0:hg   Lien encap:Ethernet  HWaddr CENSORED
          inet adr:209.44.112.91  Bcast:209.44.112.127  Masque:255.255.255.192
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth0:rt   Lien encap:Ethernet  HWaddr CENSORED
          inet adr:209.44.112.92  Bcast:209.44.112.127  Masque:255.255.255.192
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

In facter 1.5.1 and 1.5.4, this yields duplicate eth0 interfaces in the interfaces fact:

interfaces => eth0,eth1,eth0,eth0,sit0

This, in turn, breaks modules (like the munin module) which rely on the interface list to create graphs per interface:

err: Could not retrieve catalog: Puppet::Parser::AST::Resource failed with error ArgumentError: Duplicate definition: Munin::Plugin[if_eth0] is already defined in file /etc/puppet/modules/munin/manifests/plugin.pp at line 101; cannot redefine at /etc/puppet/modules/munin/manifests/plugin.pp:101 on node shell.koumbit.net

So lots of fun. :)

The fix is to be a bit more lenient in what we consider to be an interface. Patch for 1.5.4 attached. I know 1.5 master is slightly different, but it should be fairly trivial to patch.

With the patch, I get proper facts in place:

interfaces => eth0,eth1,eth0_hg,eth0_rt,sit0

Since those are “virtual” interfaces (they’re just aliases), I guess an alternative approach could be to filter out duplicates in the interfaces fact.