Fix Ubuntu resolving dns name

1.
Check your conf file.
Сorrect sample of /etc/resolv.conf:

domain mydomain.com
search mydomain.com
nameserver 192.168.1.3
nameserver 192.168.1.5

2.
Сorrect sample of /etc/nsswitch.conf:
passwd: compat
group: compat
shadow: compat
hosts: files dns
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
netgroup: nis

3. Make ping via pc's DNS name.