SSH is a powerful protocol that lets you access machines remotely and run commands on them. Rutgers has a cluster of linux machines for CS students, and I often run programs on them. Sometimes, I leave a program running for a while, and forget which machine it was on. In this situation, PDSH comes in handy. It lets me run
ps aux | grep -i <username> quickly across all the machines.
PDSH - Run SSH in Parallel
PDSH lets you run a command in parallel across a bunch of machines. I start by creating a text file with a list of machines I want to shell into:
cd.cs.rutgers.edu cp.cs.rutgers.edu grep.cs.rutgers.edu kill.cs.rutgers.edu less.cs.rutgers.edu ls.cs.rutgers.edu man.cs.rutgers.edu pwd.cs.rutgers.edu rm.cs.rutgers.edu top.cs.rutgers.edu vi.cs.rutgers.edu cpp.cs.rutgers.edu java.cs.rutgers.edu perl.cs.rutgers.edu basic.cs.rutgers.edu assembly.cs.rutgers.edu pascal.cs.rutgers.edu php.cs.rutgers.edu lisp.cs.rutgers.edu prolog.cs.rutgers.edu adapter.cs.rutgers.edu command.cs.rutgers.edu decorator.cs.rutgers.edu facade.cs.rutgers.edu flyweight.cs.rutgers.edu mediator.cs.rutgers.edu patterns.cs.rutgers.edu singleton.cs.rutgers.edu state.cs.rutgers.edu template.cs.rutgers.edu visitor.cs.rutgers.edu builder.cs.rutgers.edu composite.cs.rutgers.edu design.cs.rutgers.edu factory.cs.rutgers.edu interpreter.cs.rutgers.edu null.cs.rutgers.edu prototype.cs.rutgers.edu specification.cs.rutgers.edu strategy.cs.rutgers.edu utility.cs.rutgers.edu
Let's say I save this file as
machines.txt. I can then run a command in parallel across all these machines:
$ pdsh -R ssh -w ^machines "<command>"
Here are some things you can do with PDSH that you might find useful
Find all python processes running on these machines.
$ pdsh -R ssh -w ^machines "ps aux | grep -i python"
Kill any processes being run by my user. (Super useful if you forget to log out of a lab machine.)
$ pdsh -R ssh -w ^machines "killall -u `whoami`"
Check a specific log file for errors.
$ pdsh -R ssh -w ^machines "grep -i error /path/to/log"
It's a handy UNIX tool to have in your arsenal when working with lots of machines. Clearly, I am only showing the usage of
pdsh in the most basic way. Check out PDSH on Google Code for a more detailed description of everything PDSH can do.