How to run a Shell Script before shutdown on CentOS - linux

Question

I want to send an email when the system is going to shutdown to an email ID. I have CentOS 6.4. Below is my Script.
cat /ect/init.d/sendshtmail
#!/bin/bash
EMAIL="example#example.com"
SHUTDOWNSUBJECT="["`hostname`"] - System Shutdown"
SHUTDOWNBODY="This is an automated message to notify you that "`hostname`" is shutting down.
LOCKFILE=/var/lock/subsys/SystemEmail
echo "${SHUTDOWNBODY}" | mutt -s "${SHUTDOWNSUBJECT}" ${EMAIL}
It has the appropriate permission. While running it manually it's working perfectly. I have just symlinked it to /etc/rc0.d/ folder. By issuing below command.
ln -s /etc/init.d/sendshtmail /etc/rc0.d/K00sendshtmail
But the script is not sending any email during shutdown. Thanks in Advance.

Answer 1

Place your shell script in /etc/init.d with executable permission and symlink name should start with K##. If you want to execute your script at first place immediately after shut down then name it with K00scriptname. Script started will K will be executed first based on ascending order then script with S.
ln -s /etc/init.d/script /etc/rc0.d/K00scriptname
Shutdown command will send the stop signal to script, your script (K00scriptname) should have stop function like example
stop()
{
echo "executing scriptname"
"Your script logic"
}
case "$1" in
stop)
stop
;;
esac
Most important, K00scriptname will execute only if there would be lock file present in /var/lock/subsys folder, so do "touch /var/lock/subsys/scriptname" then check by doing shutdown.

Answer 2

Try to set executable permissions for your script. Sometimes you need to do that to activate it.
chmod 755 /etc/init.d/sendshtmail
Also try to use absolute paths for your command, while quoting the other variable as well.
echo "${SHUTDOWNBODY}" | /usr/bin/mutt -s "${SHUTDOWNSUBJECT}" "${EMAIL}"
Another attempt is to switch your user to your current user e.g.
echo "${SHUTDOWNBODY}" | su -l -c "/usr/bin/mutt -s \"${SHUTDOWNSUBJECT}\" \"${EMAIL}\"" yourusername

Answer 3

ln -s /etc/init.d/sendshtmail /etc/rc0.d/S01sendshtmail
The symlink name should begin with a S - for Start (K for Kill)
The two-digit specifies the order of execution for your script, the lowest numbered being execute first.