Postfix Failed to start : unable to set exclusive lock: Resource temporarily unavailable

Question

Postfix was running well untill I decided for some reason to restart since I updated message_size_limit

By doing this

postconf -e message_size_limit=24840000

Stopped it and Now ... Postfix wont start , It keeps on saying

fatal: open lock file /var/lib/postfix/master.lock: unable to set exclusive lock: Resource temporarily unavailable

I tried reverting the change but no luck,

Sep 23 20:47:45 example.com systemd[1]: Starting Postfix Mail Transport Agent...
Sep 23 20:47:45 example.com postfix/postfix-script[13392]: starting the Postfix mail system
Sep 23 20:47:45 example.com postfix/master[13394]: fatal: open lock file /var/lib/postfix/master.lock: unable to set exclusive lock: Resource temporarily unavailable
Sep 23 20:47:46 example.com postfix/master[13393]: fatal: daemon initialization failure
Sep 23 20:47:47 example.com postfix/postfix-script[13395]: fatal: mail system startup failed
Sep 23 20:47:47 example.com systemd[1]: postfix.service: control process exited, code=exited status=1
Sep 23 20:47:47 example.com systemd[1]: Failed to start Postfix Mail Transport Agent.
Sep 23 20:47:47 example.com systemd[1]: Unit postfix.service entered failed state.
Sep 23 20:47:47 example.com systemd[1]: postfix.service failed.

If it would help , I also installed SSL from LetsEncrypt like 2 weeks ago , perhaps that might be the cause of the problem?

Solution

Thanks to to the URL shared with @ryan-babchishin , it helped to arrive to the solution

##The Problem So I was using systemctl to start,reload,stop postfix and it was adding other hidden users , I recently updated virtualmin , and it keeps on using

#systemctl status postfix.service
#systemctl stop postfix.service
#systemctl start postfix.service

Instead of

#postfix <start/stop>

##The Solution So it resulted the master.lock being used by other users hence we can not modify , resulting to

fatal: mail system startup failed

We only need to kill the process and start postfix

Now ... Check to see if the file is there

#ls -l /var/lib/postfix/master.lock

Look for the process utilizing it

#htop 

or simply do

#fuser /var/lib/postfix/master.lock
7881

Now

#ps -ef | grep 7881
root      7881     1  0 Sep16 ?        00:00:09 /usr/libexec/postfix/master -w
postfix   9127  7881  0 10:04 ?        00:00:00 pickup -l -t unix -u
postfix   9469  7881  0 10:13 ?        00:00:00 smtpd -n smtp -t inet -u -o stress= -o smtpd_sasl_auth_enable=yes
postfix   9470  7881  0 10:13 ?        00:00:00 proxymap -t unix -u
postfix   9471  7881  0 10:13 ?        00:00:00 smtpd -n smtp -t inet -u -o stress= -o smtpd_sasl_auth_enable=yes
postfix   9472  7881  0 10:13 ?        00:00:00 anvil -l -t unix -u
postfix   9476  7881  0 10:13 ?        00:00:00 trivial-rewrite -n rewrite -t unix -u
root      9486  8671  0 10:13 pts/0    00:00:00 grep --color=auto 7881
postfix  28581  7881  0 Sep17 ?        00:00:01 qmgr -l -t unix -u

Find the Process that uses the lock file

Kill the Process

#kill 7881

Now lets get back to postfix

# postfix status
postfix/postfix-script: the Postfix mail system is not running

Now start it

# postfix start
postfix/postfix-script: starting the Postfix mail system

Postfix is running again!

Let me play Sticky Bubble on Android to relax a bit :)

Comments

[Ryan Babchishin]

Google says: math.ias.edu/~tarzadon/pages/posts/… Did you see that?

[Fahad]

Thanks for the URL , Not exactly the same problem but it helped to arrive there , Deserved the down vote