When I run
sudo the terminal is stuck for a few seconds and then outputs an error message. My terminal looks like this:
ubuntu@(none):~$ sudo true sudo: unable to resolve host (none)
What can I do to solve it?
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Two things to check (assuming your machine is called
my-machine, you can change this as appropriate):
/etc/hostname file contains just the name of the machine.
/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.
/etc/hosts and append your new hostname to the 127.0.0.1 line (or create a new line if you prefer that).
Mine looks like:
127.0.0.1 localhost localhost.localdomain 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
penguin in the above example by your new hostname as stated in the
Note, this is an answer to this question which has been merged with this one.
Your hostname (
dave00-G31M-ES2L) is not represented in
/etc/hosts. Add an
L to this line:
So it becomes:
In order to accomplish this, open a console (press Ctrl+Alt+T) and type:
sudo gedit /etc/hosts
Add the letter
L as mentioned, save and exit.
The symptom given in the question may correlate strongly with this more specific problem:
$ hostname --fqdn hostname: Temporary failure in name resolution
There are different ways that this could be resolved, one of which is to add your hostname as localhost in
/etc/hosts (as shown in several other answers). This may be the right thing to do in general, but it isn't the only possible resolution.
A "fully qualified domain name" may be supplied by an external DNS server or similar (if such is available on your network). In this case,
sudo will not complain, despite the missing entry in
sudo attempts to dereference the hostname, even though it isn't necessarily required, due to optional capabilities in the sudoers file. See sudo command trying to search for hostname.
As long as the delay isn't too long, this error message is typically harmless.
I encountered this same error message. I think this discussion thread at AWS Developer Forums is a better solution:
"Go the the VPC management console, select the VPC, click on Actions, select Edit DNS Hostnames and select Yes."
Some terminal emulators will not update prompt with the correct hostname until you close and restart the emulator (lxterminal, I'm talking to you).
I spent 30min fighting with this error after editing my hostname and hosts files and running
sudo service hostname restart until I ran
sudo hostname and saw that the hostname was the new value, even though the prompt was showning the old value.
In my case it was the problem, I changed the
man because I wanted to know if there are some parameters you can use on
hostname. Instead it changed my
man and I always got the same message like you
sudo: unable to resolve host (none)
after changing the hostname back to `localhost everything worked fine again
Everybody advises to modify
/etc/hosts. But in some cases this may not be possible (for example inside a docker container). So, I had to find a better way and I came up with this:
echo "alias sudo='sudo -h 127.0.0.1'" >> ~/.bash_aliases source ~/.bashrc
Aliases don't work in bash scripts, but we can use variables:
sudo='sudo -h 127.0.0.1'
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-##-###
linux-web-nportion, rebooted and everything was fine.
I had this same problem! I changed my VPS's name through the online admin control panel which did not change the machine name in the hosts file All I did was run:
sudo nano /etc/hosts
Then I edited it from this:
127.0.1.1 Megabyte Megabyte 127.0.0.1 localhost
127.0.1.1 Debian Debian 127.0.0.1 localhost
and that fixed my error! Hope this helped!
In case your problem is that
/etc/hostname file and
/etc/hosts, both files have your desired hostname and still your machine is showing the error
sudo: unable to resolve host
Try, forcing the hostname
sudo hostname -F /etc/hostname
You will probably still get the same error, but try logging out and logging back in. It worked for me.