arj software package provides archiver for .arj files, you can install in your Ubuntu 12.04 LTS (Precise Pangolin) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install arj
arj is installed in your system.
Make ensure the arj package were installed using the commands given below,
$ sudo dpkg-query -l | grep arj *
You will get with arj package name, version, architecture and description in a table
| Distro | Ubuntu 12 04 lts precise pangolin |
| Section | Utilities |
| Package | arj |
| Version | 3.10.22-10+deb7u1build0.12.04. |
| Description | archiver for .arj files |
| Sub Section | Utils |