Your hostname is the name of your computer.
Your fully qualified domain name is your hostname plus the domain your company uses often ending in .local.
So if the name of your computer is bob, and your company's domain is contoso.local, your computer's fully qualified domain name (FQDN) is bob.contoso.local.:
- Hostname:
bob
- Domain:
contoso.com
- FQDN:
bob.contoso.com.
In the case of a domain like contoso.local I did not use an "external" internet domain name. This name doesn't have to be the only way that you address the server.
If you make it available by its IP address you can use DNS or that IP address to allow external users to access it.
The dot at the end of the FQDN is used to indicate the empty top-level domain.
Some more information on DNS:
Edit: Thanks for the comment on .local domains RobM
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
Basically, someone has managed to convince the owners of the ccTLD 'to.' (Tonga?) to assign the A record to their own IP address. Quite a coup in the strange old world of URL shorteners.
Normally these top-levels would not have IP addresses assigned via a standard A record, but there is nothing to say that the same could not be done to .uk, .com, .eu, etc.
Strictly speaking there is no reason to have the '.' specified, though it should prevent your browser from trying other combinations like 'to.yourdomain.com' first, and speed up the resolution of the address. It might also confuse browsers, as there is no dot, but Safari at least seems to work ok with it.