As you know, I was installing a new system (the technical word I think is provisioning) on an old server (see Gtk-WARNING ** cannot open display on CentOS 7 minimal server install). As a part of the installation we tend to make the new system a munin client. If you want to start from scratch, with a munin server installation, you can follow this howtoforge tutorial. Before, we more or less installed a A Windows munin node, so it’s time to comment on the CentOS version. No rocket science here also 😀
I will suppose you’re with the latest kernel already and no graphic desktop, although if you are behind or beyond this point, there should be no problem with this procedure also. First we install munin via yum.
yum install munin...bla bla blah... Transaction Summary =============================================================== Install 1 Package (+125 Dependent packages)
Don’t be scared about the amount of packages. Munin is supposed to monitor a lot of parameters, so it needs a lot of packages. Also, by typing yum install munin, you get also the munin server packages, in case you want to upgrade the install later. Before starting munin, you should update your munin node configuration on /etc/munin/munin-node.conf. The parameters I need are:
host_name MYSERVER allow ^XXX\.YYY\.ZZ\.AA$ allow ^127\.0\.0\.1$ allow ^::1$
I assume here MYSERVER is your server’s name, known by your network, and that XXX.YY.ZZ.AA is your munin server IP address. If we start the munin service now, we will get the all kind of errors. You can check them on the log.
more /var/log/munin-node/munin-node.log Resolved [*]:4949 to [::]:4949, IPv6 Not including resolved host [0.0.0.0] IPv4 because it will be handled by [::] IPv6 Binding to TCP port 4949 on host :: with IPv6 Setting gid to "0 0" CONNECT TCP Peer: "[::XXX.YYY.ZZZ.AA]: 59416" Local: "[::ffff:SOME-IP]:4949"  Error output from fw_conntrack:  cat: /proc/net/ip_conntrack: No such file or directory  Error output from fw_forwarded_local:  Can't find conntrack information
Also, the system status should give you a similar output. This is due to two issues. The firewall must be off, or it must allow the connection with the server, and some munin plugins need to be removed or tuned up. In my case, this is done in a couple of command strikes.
> systemctl stop firewalld.service > rsync -av other-munin-client:/etc/munin/plugins/ /etc/munin/plugins/ --delete-after --progress
The less plugins you have, the better the server will handle the client. This is my list of deleted plugins.
vmstat users threads swap processes proc_pri postfix_mailvolume postfix_mailqueue open_inodes open_files netstat load irqstats interrupts if_err_something if_something fw_packets fw_forwarded_local fw_conntrack forks entropy diskstats df_inode df
Time to start it, and enable it so it comes back after a reboot
systemctl start munin-node.service systemctl enable munin-node.service
A good munin node log in my case is looking like this.
CONNECT TCP Peer: "[munin-server-ip]:57046" Local: "[local-ip]:4949"
Don’t be inpatient and wait at least 15 minutes so you have 3 points to show on the graphs. See you later or tomorrow!