Centos – Configuring the hostname on Red Hat Enterprise Linux

centosnetworkingredhat

On RHEL and similar distributions such as CentOS and OEL you can set the hostname by adding a hostname entry in /etc/sysconfig/network.

HOSTNAME=hydrogen.lan

If you don't have such an entry, the system will fall back to the default behaviour – referencing the hostname configured on the first matching entry in /etc/hosts.

192.168.92.101 hydrogen.lan hydrogen

Now, my question is. Are there any good reasons to use the direct hostname configuration in /etc/sysconfig/network or is it simply redundant in most scenarios?

Best Answer

The box in your example will have hydrogen.lan as its hostname, not hydrogen.

The only way I know of to have hostname return the short hostname and to have hostname -f return the FQDN, is to use both the mentioned options.

So add HOSTNAME=mybox to /etc/sysconfig/network and add

10.10.10.10 mybox.example.com mybox

to /etc/hosts. I like having hostname and hostname -f return different things. By default, Anaconda sets it up like you have it set up now.

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Centos – The real differences between Red Hat Enterprise Linux (RHEL) and CentOS

Short of doing installations of both and running a fancy diff between the two and manually picking through the output, there's no real way to prove to most people that they're the same. Yes, they use the same compiler, and the same linker, and the same libraries, all with the same options, but many people don't see induction as proof.

Setting the Hostname: FQDN or Short Name?

I would choose a consistent approach across the entire environment. Both solutions work fine and will remain compatible with most applications. There is a difference in manageability, though.

I go with the short name as the HOSTNAME setting, and set the FQDN as the first column in /etc/hosts for the server's IP, followed by the short name.

I have not encountered many software packages that enforce or display a preference between the two. I find the short name to be cleaner for some applications, specifically logging. Maybe I've been unlucky in seeing internal domains like server.northside.chicago.rizzomanufacturing.com. Who wants to see that in the logs or a shell prompt?

Sometimes, I'm involved in company acquisitions or restructuring where internal domains and/or subdomains change. I like using the short hostname in these cases because logging, kickstarts, printing, systems monitoring, etc. do not need full reconfiguration to account for the new domain names.

A typical RHEL/CentOS server setup for a server named "rizzo" with internal domain "ifp.com", would look like:

/etc/sysconfig/network:
HOSTNAME=rizzo
...

/etc/hosts:
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

172.16.100.13   rizzo.ifp.com rizzo

[root@rizzo ~]# hostname 
rizzo

/var/log/messages snippet:
Dec 15 10:10:13 rizzo proftpd[19675]: 172.16.100.13 (::ffff:206.15.236.182[::ffff:206.15.236.182]) - Preparing to               
 chroot to directory '/app/upload/GREEK'
Dec 15 10:10:51 rizzo proftpd[20660]: 172.16.100.13 (::ffff:12.28.170.2[::ffff:12.28.170.2]) - FTP session opened.
Dec 15 10:10:51 rizzo proftpd[20660]: 172.16.100.13 (::ffff:12.28.170.2[::ffff:12.28.170.2]) - Preparing to chroot                
to directory '/app/upload/ftp/SRRID'

Best Answer

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Setting the Hostname: FQDN or Short Name?

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