Can I have dots in a hostname?

Question

I'm using names like a.alpha for the hostname of my linux box, but it seams that these name are not completely usable. The response of a hostname shell command is correct (a.alpha). But the name printed after my user account is "user@a" instead of "user@a.alpha". When I use avahi, I can reach (by hostname) a.alpha, but not b.alpha. Is that normal?

Answer 1

Chopper is right. Due to how DNS works, the "alpha" component of "a.alpha" is considered a discrete 'label' in DNS. Using a hostname with a dot in it will cause inconsistent results from any system that consumes DNS.

Avahi does interact with DNS names, and specifically the <host-name> directive needs to have the DNS FQDN of the service in it, so it's also subject to DNS inconsistency with dotted names.

Don't use dotted name.

Answer 2

You're asking for trouble with that naming scheme due to DNS, consider a-alpha instead.