sendmail and hostnames on internal network only?

jbennett · 06-05-2012, 12:01 PM

I realize this is a pretty specific question, but in my learning process it's an issue I've come across. This is part of a learning project for me.

What I have:

CentOS 6 virtual box
OTRS Ticketing system installed and browser accessible via IP
email: otrs@example.org

This ticketing system is on a box that is on our internal network.

I'm trying to set up sendmail to relay the ticket emails to our techs and to receive email notifications from Nagios in order to generate said tickets.

I have the email address created and I am able to send/receive emails from it from within Outlook on my work computer just fine. (otrs@example.org)

My question is really related the host name of the centos virtual box. Currently, my hosts file is as follows:

Code:

127.0.0.1 otrs.example.org
127.0.0.1 localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6

I'm at the point where I need to send in a ticket to our DNS server admin and have him make the necessary additions for this server to be able to use sendmail. However, I'm not certain if I need to change my hostname on this box? I'm not sure if setting the host name of this specific box to otrs.example.org is actually wrong? I'm a bit lost at this point (as if that wasn't obvious) and would appreciate any guidance that anyone might be able to provide.

MensaWater · 06-05-2012, 12:10 PM

You can't have multiple lines for the same IP in /etc/hosts so would ordinarily have all aliases on the same line. Also it is usual to have both a short name (no domain) and a fully qualified domain name (FQDN):

Code:

127.0.0.1 otrs.example.org otrs localhost.localdomain localhost

Although by default RHEL/CentOS puts the hostname you setup in the 127.0.0.1 entry I try to change that so that it has whatever IP I've assigned to the host's primary NIC. Note that the hostname entry must be the first line in /etc/hosts regardless of which IP you use. You should also have the localhost stuff as it is used for a lot of things so if your primary NIC were IP 10.01.01.10 you'd use:

Code:

10.10.10.10 otrs.example.org otrs 
127.0.0.1 localhost.localdomain localhost

Also on CentOS/RHEL the hostname as reported by the hostname comamand and uname -n is stored in /etc/sysconfig/network. The entries in /etc/hosts are just to allow lookups of IP associated with the name for various commands (such as ping).

jbennett · 06-05-2012, 12:15 PM

Quote:

Originally Posted by MensaWater

Also on CentOS/RHEL the hostname as reported by the hostname comamand and uname -n is stored in /etc/sysconfig/network. The entries in /etc/hosts are just to allow lookups of IP associated with the name for various commands (such as ping).

So, I'm taking it that I should have the following in networking?

Code:

HOSTNAME=otrs.example.org

This is immensely helpful. Thanks!!

MensaWater · 06-05-2012, 12:23 PM

Quote:

Originally Posted by jbennett

So, I'm taking it that I should have the following in networking?

Code:

HOSTNAME=otrs.ntta.org

This is immensely helpful. Thanks!!

You could have either that FQDN or just the shortname otrs. You might want to reboot the server if you change that line as it affects what is written to syslog among other things.