Sometimes I find that some Ubuntu installations don’t have the dig command available:

[chris@work ~]$ dig +short
-bash: dig: command not found
[chris@work ~]$ 

The solution is to install the dnsutils package. For example:

[chris@work ~]$ sudo apt-get install dnsutils
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/147 kB of archives.
After this operation, 378 kB of additional disk space will be used.
Selecting previously unselected package dnsutils.
(Reading database ... 182371 files and directories currently installed.)
Unpacking dnsutils (from .../dnsutils_1%3a9.9.3.dfsg.P2-4ubuntu1.1_amd64.deb) ...
Processing triggers for man-db ...
Setting up dnsutils (1:9.9.3.dfsg.P2-4ubuntu1.1) ...
[chris@work ~]$ dig +short
[chris@work ~]$ 

Did I help you?