sudo: unable to resolve host (none)

Question

I have this issue on AWS on some servers. Whenever I run sudo the terminal is stuck doing seemingly nothing, until it finally spits out this error message. My terminal looks like this:

ubuntu@(none):~$ sudo true
sudo: unable to resolve host (none)

What can I do to solve it?

---

Update: Solved! It was all in /etc/hostname. On two of our sick servers it looked like this:

ubuntu@(none):~$ cat /etc/hostname
linux-web-n ip-10-128-##-##

While on a server without this issue we had:

ubuntu@ip-10-128-##-###:~$ cat /etc/hostname
ip-10-128-##-###

Removed the linux-web-n portion, rebooted and everything was fine. Thanks. :)

Answer 1

Two things to check (assuming your machine is called my-machine, you can change this as appropriate):

1. That the /etc/hostname file contains just the name of the machine.

2. That /etc/hosts has an entry for localhost. It should have something like:

    127.0.0.1    localhost.localdomain localhost
    127.0.1.1    my-machine
   

If either of these files aren't correct (since you can't sudo), you may have to reboot the machine into recovery mode and make the modifications, then reboot to your usual environment.

Answer 2

Edit /etc/hosts and add your new host name to the 127.0.0.1 line.

Mine looks like:

127.0.0.1       localhost
192.168.2.2     penguin

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Replace "penguin" in the above example by your new hostname as stated in the /etc/hostname file.

Answer 3

Sorry I can't help you much but, since it says "can't resolve host" try running:

hostname

And see if the output is the hostname of the machine. If not, the problem is the host configuration, not sudo.