How to install man pages on an ubuntu docker image?

Question

I use the following Dockerfile to build an image and start a container. But once I am in the container, I still can not find manpages. Does anybody know how to solve this problem?

$ cat Dockerfile 
FROM ubuntu
RUN apt -y update && apt -y upgrade
RUN apt-get -y install build-essential
RUN apt-get -y install vim
RUN apt-get -y install man
RUN apt-get -y install gawk
RUN apt-get -y install mawk

$ man man
No manual entry for man
See 'man 7 undocumented' for help when manual pages are not available.
$ find /usr/share/man /usr/local/share/man  -type f

Answer 1

There is a easier way to enable the MAN command.

In terminal, just execute the command below:

unminimize

It will ask if you like to continue [Y/n] Just press:

Y

It will take a while to finish all the processing.

After that, test this:

man man

Simple as that

Thanks to @kazushi