Setting FQDN hostname and dot

Question

I was wondering if I am editing a file such as /etc/hosts or /etc/sysconfig/network should I put a . at the end of the name. such as test.example.com.

Is there a difference? Would anything break either way.

Answer 1

According to man hosts:

Host names may contain only alphanumeric characters, minus signs ("-"), and periods ("."). They must begin with an alphabetic character and end with an alphanumeric character.

Answer 2

Entries in /etc/hosts are never expanded with a domain, it's a simple table lookup, and hence, trailing dots are meaningless and likely to cause issues. Also as mentioned in another answer, the specification for /etc/hosts rules them out (for this reason).

Answer 3

I have never seen anyone use a trailing dot there, so you probably shouldn't. Even though nothing might break right now, it's just tempting fate, as something might not expect it.

Answer 4

Trailing dot is not meaningless. If you try to access a host with FQDN(which includes trailing dot), your application will lookup the name from DNS not /etc/hosts if the hostname in /etc/hosts does not have trailing dot.