Linux – Temporarily increasing sudo’s timeout for the duration of an install script

linuxpasswordscriptingsudo

I'm trying to write a script that will install a bunch of software and I'd like to not have to run everything as root, so I'd like to be able to prompt for a password and then go about the install, using sudo or su to get privileges when I need them.

I was doing a sudo -v to prompt for a password at the beginning of the script, and then just using sudo normally later on. This works great until I get to a single install that takes over the timeout.

I'd rather not have to permanently increase the timeout. Is there a way I can increase sudo's timeout for the current session only?

Best Answer

You can setup a loop that runs in the background to periodically execute "sudo -v", the trick of course is getting the loop to cleanly terminate when your script terminates. So there has to be some type of communication between the two processes; tmp files are fine for this, and they can easily be cleaned up after the script runs, too. (An install script usually does this, anyway.)

For example (remove the 'echo' statements to use this; these just show it "working"):

#!/bin/bash
log=running_setup.txt
sudo_stat=sudo_status.txt

echo "========= running script $$ ========"
echo $$ >> $sudo_stat
trap 'rm -f $sudo_stat >/dev/null 2>&1' 0
trap "exit 2" 1 2 3 15

sudo_me() {
 while [ -f $sudo_stat ]; do
  echo "checking $$ ...$(date)"
  sudo -v
  sleep 5
 done &
}


echo "=setting up sudo heartbeat="
sudo -v
sudo_me

echo "=running setup=" | tee $log
while [ -f $log ]
do
 echo "running setup $$ ...$(date) ===" | tee -a $log
 sleep 2
done

# finish sudo loop
rm $sudo_stat

Then you'll see... (note: the pid is put into the tmp file, just so you can easily kill it. It's not necessary, though):

$ ./do_it.sh
========= running script 6776 ========
=setting up sudo heartbeat=
[sudo] password for user: 
=running setup=
checking 6776 ...Wed May  4 16:31:47 PDT 2011
running setup 6776 ...Wed May  4 16:31:48 PDT 2011 ===
running setup 6776 ...Wed May  4 16:31:50 PDT 2011 ===
running setup 6776 ...Wed May  4 16:31:52 PDT 2011 ===
checking 6776 ...Wed May  4 16:31:53 PDT 2011
running setup 6776 ...Wed May  4 16:31:54 PDT 2011 ===
<ctrl-c>  (cleans up files, then exits)
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