How can I automate running commands remotely over SSH to multiple servers in parallel?

Question

I've searched around a bit for similar questions, but other than running one command or perhaps a few command with items such as:

ssh user@host -t sudo su - 

However, what if I essentially need to run a script on (let's say) 15 servers at once. Is this doable in bash? In a perfect world I need to avoid installing applications if at all possible to pull this off. For argument's sake, let's just say that I need to do the following across 10 hosts:

1. Deploy a new Tomcat container
2. Deploy an application in the container, and configure it
3. Configure an Apache vhost
4. Reload Apache

I have a script that does all of that, but it relies on me logging into all the servers, pulling a script down from a repo, and then running it. If this isn't doable in bash, what alternatives do you suggest? Do I need a bigger hammer, such as Perl (Python might be preferred since I can guarantee Python is on all boxes in a RHEL environment thanks to yum/up2date)? If anyone can point to me to any useful information it'd be greatly appreciated, especially if it's doable in bash. I'll settle for Perl or Python, but I just don't know those as well (working on that). Thanks!

Answer 1

You can run a local script as shown by che and Yang, and/or you can use a Here document:

ssh root@server /bin/sh <<\EOF   wget http://server/warfile    # Could use NFS here   cp app.war /location   command 1   command 2   /etc/init.d/httpd restart   EOF  

Answer 2

Often, I'll just use the original Tcl version of Expect. You only need to have that on the local machine. If I'm inside a program using Perl, I do this with Net::SSH::Expect. Other languages have similar "expect" tools.