How to Fix : sudo: unable to resolve host my_user: No such file or directory

If you have changed the hostname of your Linux PC, by using command from there are chances you may get an warnings like below everytime you type some commands with sudo permission in terminal and taking considerable time to return the command output,

$ time sudo cat /proc/version
sudo: unable to resolve host laptop: No such file or directory

real	0m30.039s
user	0m0.012s
sys	0m0.004s

So, it shows it took almost 30 sec for simple cat command to return and also returned an error/warning like “sudo: unable to resolve host laptop: No such file or directory” where “laptop” is my hostname.

To resolve this, we need to make sure following files has contents like below,

 $ cat /etc/hostname 

This should show your existing hostname you set using hostnamectl command.

 $ sudo vim /etc/hosts 

has follwing line, your_hostname

Replace, “your_hostname” with proper hostname you have, in my case it should “laptop” as hostname.

Now try again same comamnd as above,

 $ time sudo cat /proc/version

real	0m0.012s
user	0m0.000s
sys	0m0.008s 

and you see now warning, and very less time it took to execute that command.

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