====== Multi server update script ======

This script updates all Debian servers from the list by apt-get update and upgrade commands. It is highly recommended you have key authorization on all systems or you will have to insert all passwords...

<code>#!/bin/bash

SERVERS=(
    server1.com
    server2.com
    etc.com
)

keychain ~/.ssh/id_dsa -Q -q --lockwait 5 --attempts 5 --nolock;
source ~/.keychain/*-sh;

for SERVER in "${SERVERS[@]}"; do
    echo "Working on $SERVER";
    # user-defined command?
    if [ -z "$1" ]; then
        ssh root@$SERVER 'apt-get -y update; apt-get -y upgrade';
    else
        ssh root@$SERVER "$1";
    fi
done</code>

Could be...

<code>$ up-servers 'cat /etc/debian_version'
Working on server1.domain.com
3.1
Working on server2.domain.com
3.1
Working on server3.domain.com
3.1
...
</code>