sudo: unable to resolve host dhcppc1

Question

I get following error whenever i do something like:

sudo apt-get install sddm
sudo: unable to resolve host dhcppc1

It happened when i upgrade from 14.04 to 16.04.

---

/etc/hosts

127.0.0.1       localhost.localdomain localhost
127.0.1.1       mlibre-ThinkPad-E555
# 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

Update

I have another problem. whenever i reboot system, this problem happen again.

/etc/hostname

localhost

Answer 1

Your computer's name (hostname) is set to dhcppc1, but dhcppc1 is not in /etc/hosts and it cannot be resolved by DNS. The way your /etc/hosts looks your computer's name should be mlibre-ThinkPad-E555. You must resolve this mismatch.

Answer 2

First of all try rebooting your system. If the problem persists then try these-

Sol-1 Go to system-settings-> system-details. And there in the overview panel, rename your device to the same device name as mentioned in the /etc/hosts.

This method will change the device name in the etc/hostname without asking you for the admin password.

Sol-2 Type the following in the terminal

sudo gedit ~/etc/hosts

(Although the error will appear here but the terminal will accept your password). There modify the device name to the same name as in etc/hostname file.

This should resolve the mismatch in the hosts and hostname file.