By default, Ubuntu linux doesn’t have a chm viewer and a rar utility installed so you have to install them by yourself if you want to be able to view chm files which is the most common format for ebooks. Rar utility on the other hand is used to decompress archived files compressed using the rar archiving program such as winrar in windows or rar in linux.

and here’s how to install these programs.

For CHM viewer, we will install chmsee, but you can install any CHM viewer of your preference.

sudo apt-get install chmsee

To be able to open rar compressed files through File Roller, the unrar utility must be installed first.

sudo apt-get install unrar