Error shortly after an update.

[Silvernail]

I've been getting this error for a couple of days. What is causing it and what do I need to do to eliminate it?

dave@Dafydd:~$ sudo youtube-dl -U
sudo: unable to resolve host Dafydd
[sudo] password for dave:

And then all seems to work.

[fdrake]

what is the output of

cat /etc/hostname

[Silvernail]

dave@Dafydd:~$ cat /etc/hostname
Dafydd
dave@Dafydd:~$
-rw-r--r-- 1 root root 7 Feb 15 01:56 hostname
Should it be somewhere else?

dave@Dafydd:/etc$ sudo grep -Ri 'Dafydd' *
sudo: unable to resolve host Dafydd
[sudo] password for dave:
Binary file aliases.db matches
cups/printers.conf.O:Location Dafydd
cups/printers.conf:Location Dafydd
hostnameafydd
postfix/main.cf:myhostname = Dafydd
postfix/main.cf:mydestination = embarqmail.com, Dafydd, localhost.localdomain, localhost
printcap:ML-2010|Samsung ML-2010:rm=Dafydd:rp=ML-2010:
dave@Dafydd:/etc$

[fdrake]

any chance that your hostname is missplelled in /etc/hosts ? post your "cat /etc/hosts "
did you play with the domanin name somewhere in your net settings?