Running daemon programs with the interactive xxgdb debugger

If you have X Windows installed on the Postfix machine, then an interactive debugger such as xxgdb can be convenient.

Edit the debugger_command definition in /etc/postfix/main.cf so that it invokes xxgdb:

/etc/postfix/main.cf:
    
debugger_command =
         PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin
         xxgdb $
daemon_directory/$
process_name $
process_id & sleep 5

Be sure that gdb is in the command search path, and export XAUTHORITY so that X access control works, for example:

% setenv XAUTHORITY ~/.Xauthority (csh syntax)
$ export XAUTHORITY=$HOME/.Xauthority (sh syntax)

Append a -D option to the suspect daemon definition in /etc/postfix/master.cf, for example:

/etc/postfix/master.cf:
    smtp      inet  n       -       n       -       -       smtpd -D

Stop and start the Postfix system. This is necessary so that Postfix runs with the proper XAUTHORITY and DISPLAY settings.

Whenever the suspect daemon process is started, a debugger window pops up and you can watch in detail what happens.