How to Install and Configure a Linux Email System
Prev	Postfix Pre-Installation Steps	Next

1.4 Postfix Pre-Installation Steps

The first step before installing Postfix is to make sure that Sendmail is not already running on your system. You can check for this using the following command:

 	/sbin/service sendmail status

If sendmail is not running the following output will be displayed:

 	sendmail is stopped

If sendmail is running you will see the following:

	sendmail is running 

If sendmail is running on your system it is necessary to stop it before installing and configuring Postfix. To stop sendmail run the following command as super user:

	/sbin/service sendmail stop

The next step is to ensure that sendmail does not get restarted automatically when the system is rebooted. The first step is find out which run levels will automatically start sendmail. To do this we can use the chkconfig commandline tool as follows:

 	/sbin/chkconfig --list | grep sendmail

The above command will typically result in output similar to: 

	sendmail     0:off   1:off   2:on   3:off   4:on    5:on   6:off

This means that if the system boots into runlevels 2, 4 or 5 then the sendmail service will automatically start. To turn off sendmail we can once again use the sendmail command as follows:

	/sbin/chkconfig sendmail off

The chkconfig defaults to changing the settings for runlevels 2, 3, 4 and 5. If you can configure for specific runlevels using the –levels command line option if necessary.

To verify the settings run chkconfig one more time as follows: 

	/sbin/chkconfig --list | grep sendmail

And check that the output is as follows:

	sendmail        0:off  1:off   2:off   3:off  4:off   5:off   6:off 

Sendmail is now switched off and configured so that it does not auto start when the system is booted. We can now move on to installing Postfix.

How to Install and Configure a Linux Email System
Prev	Postfix Pre-Installation Steps	Next