fqdn does not accept terminal dot

[Evan Carroll]

A fully qualified domain is not

    foo.bar.com

But instead,

    foo.bar.com.

Otherwise the fqdn hit up the resolver and searches on the network for a matching host. So if the resolver is on network

    foobar.com.

And you query for `foo.bar.com` it'll look up a host by that name

    foo.bar.com.foobar.com.

To stop this you fully-qualify with a terminal dot. This creates a problem because hostname does not accept a terminal dot,

sudo hostname host-10-2-65-89.openstack.build.
hostname: the specified hostname is invalid

And cloud-init blindly submits the input to hostname. Which is weird, because you have to supply an fqdn which actually can _not_ currently be a fqdn. The desired fix for this would be to trim off the dot from the value supplied in fqdn, before providing it to hostname.

[Evan Carroll (evancarroll)]

This is inspired on my question and self-research here,

https://devops.stackexchange.com/q/15678/18965

[James Falcon (falcojr)]

Thanks for this bug report. Since hostname setting is implementation dependent, we should include a note in the docs that some tools don't accept the trailing dot.

[James Falcon (falcojr)]

Doc was updated in https://github.com/canonical/cloud-init/pull/1365

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/3962