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shell script to run command in remote servers using ssh

 Hello Techie's,


what if, You have a single shell script whics helps to exexute any command on the remote servers ? 

Sound's Cool ?

Let's Say you want to check the Java version in your RHEL servers or you just want to know the contents of the particular directory or current backround process running on the server or any commands which comes to your mind, Below shell script is your one stop solution.

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#!/bin/bash
#This script helps to execute commands on multiple servers with the help of ssh
#List of servers - one server per line
SERVER_LIST=/home/directory/server
#option for the SSH commands
SSH_OPTIONS='-o ConnectTimeout=2'
#Displaying the usage of the script and exit messages
usage() {echo "usage: ${0} { -nsv } [-f FILE] CMD" >&2
echo "Execute CMD as a single command on every server" >&2 
echo "  -f FILE use FILE for the list of servers. Default ${SERVER_LIST}." >&2
echo "  -n Dry run mode, Given command will be displayed not executed." >&2
echo "  -s Run the command with sudo user privillege." >&2
echo "  -v Enables verbose mode to display the name of server in which cmd is executed." >&2
exit 1
}
#make sure the script is not excecuted with sudo user privilege.
if [[ "${UID}" -eq 0 ]]
then 
echo " Do not execute this script as root. use the option -s instead." >&2
usage
fi
#Parse the options
while getopts f:nsv OPTION
do
case ${OPTION} in
f) SERVER_LIST="${OPTARG}" ;;
n) DRY_RUN='true' ;;
s) SUDO='sudo' ;;
v) VERBOSE='true' ;;
?) usage ;;
esac
done
#Remove the options while leaving the remaining arguements.
shift "$(( OPTIND -1 ))"
#If the user not provided atleast one arguements. give them help.
if [[ "$#" -lt 1 ]]
then
usage
fi
#Anything that remains on the command line to be treated as single command.
COMMAND="${@}"
#Make sure the serverlist file exists.
if [[ ! -e "${SERVER_LIST}" ]]
then 
echo "cannot open server list file ${SERVER_LIST}." >&2
exit 1
fi
#If command failed in any server below condition helps
EXIT_STATUS='0'
#Loop through the server list
for SERVER in $(cat ${SERVER_LIST})
do 
if [[ "${VERBOSE}" = 'true' ]]
then
echo "${SERVER}"
fi
SSH_COMMAND="ssh ${SSH_OPTIONS} ${SERVER} ${SUDO} ${COMMAND}"
#if it is a dry run, do not execute anything, just echo it.
if [[ "${DRY_RUN}" = 'true' ]]
then
echo "DRY_RUN: ${SSH_COMMAND}"
else
${SSH_COMMAND}
SSH_EXIT_STATUS="${?}"
#capture non-zero exit status from the SSH_CMD and report to the user.
if [[ "${SSH_EXIT_STATUS}" -ne 0 ]]
then 
EXIT_STATUS="${SSH_EXIT_STATUS}"
echo "Execution on ${SERVER} failed." > &2
fi
fi
done
exit ${EXIT_STATUS}

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