Changing Contents in a File in Every Node

Occasionally you may want to change a a single string inside of a file that is on every compute node. If the file was the same on every node you could change it in one place and then copy it out like so:

$ act_cp -g nodes /path/to/file

Some config files are unique to each node, but may have a recurring string that you want to change on each one of them. In the following example we will use the ‘act_exec’ command paired with a simple ‘sed’ search and replace command in order to change an IP address.

$ act_exec -g nodes "sed -i 's/10.1.1.254/10.1.1.250/' /etc/sysconfig/network-scripts/ifcfg-eth0"

In the above example I already know that each one of my nodes ifcfg-eth0 files has a gateway of 10.1.1.254 set, and I want to change this to 10.1.1.250 for every one of my nodes. This is an easy way to accomplish simple replacements across your entire cluster.