When I have restarting the postfix server I am facing the below error ::
postfix-out/master: fatal: open lock file pid/master.pid: cannot create file exclusively: Permission denied
I having a centos server.
This file is created every time postfix starts.
In debian the file is created in /var/lib/postfix/master.lock, you have to looking for the directoyr of your postfix an check the permissions and the owners of it.
You can use this command to fix permissions on postfix files and directories.
The file that controls these permissions is located here:
There may have been a stale master.pid file or or existing postfix process running, to clear these you could have done: