Home / server / Questions / 155797
In Process
Ivan
Asked: 2010-06-29 20:45:13 +0800 CST

hostname -f says "hostname: the specified hostname is invalid". Guess why?

  • 772

hostname -f says "hostname: the specified hostname is invalid". The hostname (FQDN) specified in /etc/hostname is also listed in /etc/hosts and is pingable. No actual DNS server yet of the host knows. Is this a reason of the error reported or something else? (the OS is Ubuntu 10.04 Server).

Update: registering the host at a DNS server (so that the name can be successfully resolved via Internet) did not help.

ubuntu domain-name-system hosts hostname

5 Answers

  1. From this thread on Ubuntu Forums.

    Apparently the underscore is an illegal character for hostnames. I had one in my hostname, and it gave me your failure message. Maybe you're getting something similar.

    • 14

  2. Check the configuration of:

    /etc/host.conf
/etc/nsswitch.conf

    host.conf should have "order hosts, bind" and nsswitch.conf should have "hosts: files dns" at a minimum. Possibly you've got something out of whack that's searching only DNS and not your local files?

    • 3

  3. /etc/hostname should only contain the hostname and not a full FQDN.

    • 1

  4. hostname -f relies on DNS working.

    What does:

    host `cat /etc/hostname`

    print?

    • 1

  5. You can edit your hostname at /etc/hostname or directly from the CLI like this:

    echo "<desired_hostname>" > /etc/hostname hostname -F /etc/hostname

    For systems that support it (such as Ubuntu 18.04+), you can also use hostnamectl like this:

    hostnamectl set-hostname <desired_hostname>

    Then reboot or login/logout and you should see the latest hostname, regardless of illegal characters like underscores.

    • 0