Languages/Bash/RunUpdates

Introduction

This script is used in our programming labs for doing unattended changes on all machines. It will be run once every reboot, fetch the necessary script from a ssh server and execute it.

Prerequisites

• A ssh accessible server

Setup

• Log into the machine to be updated
• Copy this script into root/run-updates.sh, the REMOTE_PATH should be updated to match your environment.

#!/bin/bash
#
# Update script
#
# * This script will fetch update scripts from REMOTE_PATH
# * Update scripts should be named 1.sh, 2.sh, ...
# * REMOTE_PATH should be accessible through ssh, without password (public key login)
# * The file LAST in DEST will hold the last script downloaded regardless of the success of executi$
 
REMOTE_PATH=user@ssh-server.example.com:
 
DEST=/usr/share/heivs/heivsupdate
 
mkdir -p $DEST
cd $DEST
 
# The file named LAST will hold the last update number
# Create it if it does not exist
#
if [ ! -e LAST ]
then
        CURRENT=0
        echo -n $CURRENT > LAST
fi
CURRENT=`cat LAST`
 
while [ 1 ]
do
        ((CURRENT++))
        scp -q $REMOTE_PATH$CURRENT.sh .
        if [ ! -e $CURRENT.sh ]
        then
                echo nothing new
                exit 0
        fi
        echo -n $CURRENT > LAST
        ./$CURRENT.sh
done

• create a RSA key for remote login into /root/.ssh/id_rsa (with an empty passphrase)

ssh-keygen -t rsa

• copy the id_rsa.pub key into the ssh server
• create a RSA key for remote login into /root/.ssh/id_rsa

ssh user@ssh-server.example.com mkdir -p .ssh
cat /root/.ssh/id_rsa.pub | ssh user@ssh-server.example.com 'cat >> .ssh/authorized_keys'

• edit the root crontab ("crontab -e")

@reboot /root/run-updates.sh >/dev/null 2>&1

Update scripts

Update scripts should be placed into the user@ssh-server.example.com directory. The file name should be 1.sh, 2.sh, ...