ubuntu - E: Could not perform immediate configuration on 'util-linux'. Please see man 5 apt.conf under APT::Immediate-Configure for details. (2)

If you are facing this error on your ubuntu or debian system. Run following commands.

# sudo apt-get upgrade -y

# sudo apt-get install upstart-job

# sudo apt-get dist-upgrade -y

Ubuntu - E: Package has No installation candidate

If you are facing this error on ubuntu, Run following command.

# sudo apt-get update

Postfix - master dead but pid file exists

Stop and start postfix. Do not restart, use individual commands for stop & start.

If you are still facing the problem
Remove /var/spool/postfix/pid/master.pid and /var/lock/subsys/postfix
Stop and start postfix

If you are still facing the problem, Check what is running on port 25

# netstat -lnp | grep :25

Kill the process and start postfix again.