Example script for Spigot Forums on controlling multiple servers over SSH

control_all.sh

#!/bin/bash

# Specify the servers here in an array
serverip[0]="10.10.10.2"
serverip[1]="10.10.10.3"
serverip[2]="10.10.10.4"
serverip[3]="10.10.10.5"
serverip[4]="10.10.10.6"
serverip[5]="10.10.10.7"

# Specify the port the servers all use for SSH (too lazy to make it work
serverport[0]="2222"
serverport[1]="3333"
serverport[2]="4444"
serverport[3]="5555"
serverport[4]="6666"
serverport[5]="7777"

# This gets an integer of the number of array items and stores it as a variable
numservers=${#serverip[@]}

# This will port test the SSH port of the server and return a value depending upon the servers state.
ping_server() {
    if [ -z "$1" ] ; then
        # No variable sent, so exit (unlikely as this is a function)
        exit 1
    else
        if timeout 1 bash -c "echo >/dev/tcp/${serverip[$i]}/${serverport[$i]}" ; then
            # Server is online, so return a 0 (okay) to whatever called this function.
            return 0
        else
            # Server is offline, so return a 1 (error) to whatever called this function.
            return 1
        fi
    fi
}

# This function will test the server and then run the command through SSH
run_cmd() {
    # This sets a temporary variable ("i") to 0, each time it loops it then increments it (adds 1). Once "i" is greater than the number of server IPs it will move on (the function will be complete).
    for ((i=0;i<$numservers;i++)); do
        # If the server is available, do the SSH command
        if ping_server ${serverip[$i]}  ; then
            echo "${serverip[$i]} is online:"
            ssh -i ~/.ssh/id_rsa -p ${serverport[$i]} ${serverip[$i]} "$1"
        else
            # Tell the user the server is unavailable, but don't exit because the loop needs to continue
            echo "${serverip[$i]} is offline"
        fi
    done
}


if [ -z "$1" ] ; then
    # No argument sent, so exit.
    echo "You must supply a command!"
    exit 1
else
    # Send the argument to the function.
    run_cmd "$1"
fi

exit 0