Category Archives: Bash Scripts

26Aug 2015

Autoreboot servers one by one

After updating multiple servers I had a need to reboot them one by one. Main issue was to automate that, so the script would wait for the node to become reachable before rebooting next one. Here’s the simple one-liner for that:

for i in $(grep "staging-.*[0-9]" /etc/hosts|awk '{print $2}'|grep -v "fw"); do echo $i; echo "press any key to continue"; read; ssh $i "reboot"; sleep 30; uptime=0; while [ $uptime -ne "1" ]; do uptime=$(ssh -o ConnectTimeout=300 -q $i "uptime"|awk '{print $3}'|tr -d ","); echo -n $uptime" "; done; echo $i" rebooted, press any key"; read; done

for i in $(grep "staging-.*[0-9]" /etc/hosts|awk '{print $2}'|grep -v "fw"); do echo $i; echo "press any key to continue"; read; ssh $i "reboot"; sleep 30; uptime=0; while [ $uptime -ne "1" ]; do uptime=$(ssh -o ConnectTimeout=300 -q $i "uptime"|awk '{print $3}'|tr -d ","); echo -n $uptime" "; done; echo $i" rebooted, press any key"; read; done

16Jul 2014

Sed replace multiple files with pattern

by root ⋅ Leave a Comment

Imagine you have couple of files: host1.cfg, host2.cfg, host3.cfg and you want to replace “hostname1”, “hostname2”, “hostname3” in each file at once to something like “hostname1-backup”. Here’s simple sed oneliner which will do that:

sed -ri "s/hostname([1-3])/hostname\1-backup/g" host*.cfg

1	sed -ri "s/hostname([1-3])/hostname\1-backup/g" host*.cfg

11Jul 2014

Simple script for any cronjob to avoid multiple instances of commands running

by root ⋅ 1 Comment

Sometimes you want to run one cronjob command at a time. Like rsync something or any other command which could interfere the next run. Imagine cronjob runs the rsync every 5 minutes. To avoid running multiple rsyncs at same time we can use helping script which creates the lock while rsync is running and removes it when rsync is done. So the script itself is below. Adapt it to your needs. Do you have idea how it can be improved or optimized? Leave a comment!

#!/bin/sh
LOCKFILE=/tmp/script.lock
if [ -e $LOCKFILE ]; then
   exit 1
else
   touch $LOCKFILE
   ionice -c3 rsync
   rm -f $LOCKFILE
   exit 0
fi

#!/bin/sh

LOCKFILE=/tmp/script.lock

if [ -e $LOCKFILE ]; then

exit 1

else

touch $LOCKFILE

ionice -c3 rsync

rm -f $LOCKFILE

exit 0

UPD: you can add the trap to the script in case it gets killed accidentally, to remove the lockfile. Just before first if insert:

trap "{ rm -f $LOCKFILE ; exit 255; }" SIGTERM EXIT

1	trap "{ rm -f $LOCKFILE ; exit 255; }" SIGTERM EXIT