Linux Server Hacks, Volume Two

Hack #29. Execute Commands Simultaneously on Multiple Servers

Run the same command at the same time on multiple systems, simplifying administrative tasks and reducing synchronization problems.

If you have multiple servers with similar or identical configurations (such as nodes in a cluster), it's often difficult to make sure the contents and configuration of those servers are identical. It's even more difficult when you need to make configuration modifications from the command line, knowing you'll have to execute the exact same command on a large number of systems (better get coffee first). You could try writing a script to perform the task automatically, but sometimes scripting is overkill for the work to be done. Fortunately, there's another way to execute commands on multiple hosts simultaneously.

A great solution for this problem is an excellent tool called multixterm, which enables you to simultaneously open xterms to any number of systems, type your commands in a single central window and have the commands executed in each of the xterm windows you've started. Sound appealing? Type once, execute many—it sounds like a new pipelining instruction set.

multixterm is available from http://expect.nist.gov/example/multixterm.man.html, and it requires expect and tk. The most common way to run multixterm is with a command like the following:

	$ multixterm -xc "ssh %n" host1 host2

This command will open ssh connections to host1 and host2 (Figure 4-1). Anything typed in the area labeled ...