[update] Added more detail about different RAR packages and Ubuntu 8.04.
Downloaded a file compressed in the RAR format and found that Archive Manager couldn’t open it? RAR support can’t be included in Ubuntu by default because it’s proprietary, but installing it is simple.
There are two options for opening RAR files in Ubuntu:
unrar-freeis an open source project for opening RAR files. However, this package may not be able to handle all types of RAR archives. You need to have the Ubuntu universe repository enabled to install this package.
Install unrar-free from the package unrar-free (click the link to install), or by running the command below in your terminal:
sudo apt-get install unrar-free
The package unrar is not open source, but should be able to open any RAR files you can find. This is likely the option you want. You need to have the Ubuntu multiverse repository enabled to install this package.
unrarfrom the package unrar (click the link to install), or by running the command below in your terminal:
sudo apt-get install unrar
After either of these package are installed, RAR archives will open seamlessly in Ubuntu’s archive manager.
You may also be interested in installing support for the open source 7z archive format.