If you want to execute a command on a set of nodes, you can install and use something dsh or parallel-ssh on your ubuntu.
Or you can use the following few lines of code.
This will come in handy when you don't have sudo access to install one of the above mentioned tools.

Save the following lines of code and name the file parallel.sh (you can improvise - add it to path, etc)

#!/bin/bash

P1=""
for i in `cat $1`
do
        ssh $i "$2" | sed "s/^/$i: /" &
        P1=$P1" "$!
done
wait $P1


Create a host files with each line in the following format and save the file
<username>@<ip-address>

eg:
user1@10.1.1.1
user1@10.1.1.2
user1@10.1.1.3
user2@10.1.1.4

Execute a command on all the nodes using parallel.sh as follows

./parallel.sh <host-file-name> "<command>"

eg:

./parallel.sh host-file "pwd"