Ubuntu ERROR: sudo: unable to resolve host ubuntu: Name or service not known

ubuntu系统报错：sudo: unable to resolve host ubuntu: Name or service not known

检查一下，

ubuntu@ubuntu:~/mc$ cat /etc/hostname
ubuntu
ubuntu@ubuntu:~/mc$ cat /etc/hosts
127.0.0.1 localhost

# 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
ff02::3 ip6-allhosts

修改一下，

sudo vim /etc/hosts

添加了一行"127.0.1.1 ubuntu"（也可以是127.0.0.1 ubuntu），如下，

127.0.0.1 localhost
127.0.1.1 ubuntu

# 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
ff02::3 ip6-allhosts

再检查 

username@ubuntu ~ $ cat /etc/hostname
ubuntu

username@ubuntu ~ $ cat /etc/hosts
127.0.0.1       localhost
127.0.1.1       ubuntu

# 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
ff02::3 ip6-allhosts

问题解决。