Linux sudo is working slow after changing the hostname

you probably need to edit /etc/hosts to reflect your new hostname

otherwise it tries to find info about it via DNS (and timeouts, most probably)

look for:

127.0.0.1  localhost  oldname

and change to:

127.0.0.1  localhost  newname

Of course change only the line corresponding to oldname. Above I gave an an example of a machine which isn't connected to the net...

Below I give an example of a machine which have an IP:

127.0.0.1  localhost
a.b.c.d    oldname     <-- just edit that line

Problem solved. I describe to help others.

I've had the same problem. All configurations were correct, but login via ssh and sudo were extremely slow.

cat /etc/hostname was correct, but something did not work.

I solved by changing the hostname NOT from the file but by the command

hostname name-of-the-host

In this way the problem has disappeared. Probably using the hostname command are done other operations and the modification is more complete than just modifying the /etc/hostname file manually.