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I have an Ubuntu machine, and I've been trying to set up Munin on port 4949. I have it running, and I can connect to port 4949 from the local machine, but connections from external machines keep timing out. I've already set allow ^.*$ in the configuration, so it shouldn't refuse any connections.

If I run lsof I get:

deployer@rc:~$ sudo lsof | grep munin
/usr/sbin 31863       root    2w      REG              202,1     78531     189176 /var/log/munin/munin-node.log
/usr/sbin 31863       root    3r      REG              202,1      6778     591661 /usr/sbin/munin-node
/usr/sbin 31863       root    4w      REG              202,1     78531     189176 /var/log/munin/munin-node.log
/usr/sbin 31863       root    5u     IPv6           42450001       0t0        TCP *:munin (LISTEN)

I can't tell if it's a firewall issue or not. How can I tell if inbound connections are successfully reaching port 4949?

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Which version of ubuntu? –  becomingwisest Jan 11 '13 at 23:14

2 Answers 2

This will show what daemons are listening on what ports.

# lsof | grep TCP | grep LISTEN

You'll want to see *:4949 to confirm that Munin is bound on all interfaces.

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This does not report anything on 4949, but I can telnet to localhost on port 4949 and get the Munin service all the same. –  Chris B. Jan 11 '13 at 20:51
    
Does it show anything for munin? Can you add the output of the command suggested? –  becomingwisest Jan 11 '13 at 21:10
    
I added the lsof output to the question. –  Chris B. Jan 11 '13 at 21:15
    
That looks fine, assuming you have munin 4949/tcp # Munin Graphing Framework in /etc/services. –  David Schwartz Jan 11 '13 at 21:26
    
I have munin 4949/tcp lrrd # Munin so I suppose that's fine? –  Chris B. Jan 11 '13 at 21:29

Since you're on Ubuntu, you likely have ufw installed to manage your firewall. What's the output of

sudo ufw status

If you need to add a rule to allow inbound to TCP port 4949, you can do so with the following:

sudo ufw allow proto tcp from 192.168.0.0/24 to 192.168.0.1 port 4949

You can also check to see what interfaces you're listening on with

sudo netstat -tanp

Also, nmap is a great tool to check from another machine what ports are open, but if it's not a LAN setup you need to be careful scanning a public IP.

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This is running in the cloud, so Rackspace is running the firewall. ufw is inactive. –  Chris B. Jan 11 '13 at 21:12
    
Ah, I see -- what's the netstat output? How do you open or close ports, or otherwise manage the firewall? –  nedm Jan 11 '13 at 21:14
    
When we need to open and close ports, we call them on the phone and put in a support request. They claim they can see packets hitting the machine, but since Munin isn't responding I don't necessarily believe them, and was trying to verify. –  Chris B. Jan 11 '13 at 21:27
    
OK, so does netstat list the port? Your lsof output shows it listening on IPv6, does it have an IPv4 address assigned as well or only IPv6? –  nedm Jan 11 '13 at 21:32
    
The only listing for munin in netstat is tcp6 0 0 :::4949 :::* LISTEN 31863/munin-node –  Chris B. Jan 11 '13 at 21:38

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