Q: How to add extra repositories?

1. Read General Notes

2. sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup
   sudo gedit /etc/apt/sources.list

3. Find this section

   ...
   ## Uncomment the following two lines to fetch updated software from the network
   # deb https://us.archive.ubuntu.com/ubuntu hoary main restricted
   # deb-src https://us.archive.ubuntu.com/ubuntu hoary main restricted
   
   ## Uncomment the following two lines to fetch major bug fix updates produced
   ## after the final release of the distribution.
   # deb https://us.archive.ubuntu.com/ubuntu hoary-updates main restricted
   # deb-src https://us.archive.ubuntu.com/ubuntu hoary-updates main restricted
   
   ## Uncomment the following two lines to add software from the 'universe'
   ## repository.
   ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
   ## team, and may not be under a free licence. Please satisfy yourself as to
   ## your rights to use the software. Also, please note that software in
   ## universe WILL NOT receive any review or updates from the Ubuntu security
   ## team.
   # deb https://us.archive.ubuntu.com/ubuntu hoary universe
   # deb-src https://us.archive.ubuntu.com/ubuntu hoary universe
   
   # deb https://security.ubuntu.com/ubuntu hoary-security main restricted
   # deb-src https://security.ubuntu.com/ubuntu hoary-security main restricted
   
   # deb https://security.ubuntu.com/ubuntu hoary-security universe
   # deb-src https://security.ubuntu.com/ubuntu hoary-security universe

4. Replace with the following lines

   ## Uncomment the following two lines to fetch updated software from the network
   deb https://us.archive.ubuntu.com/ubuntu hoary main restricted
   deb-src https://us.archive.ubuntu.com/ubuntu hoary main restricted
   
   ## Uncomment the following two lines to fetch major bug fix updates produced
   ## after the final release of the distribution.
   deb https://us.archive.ubuntu.com/ubuntu hoary-updates main restricted
   deb-src https://us.archive.ubuntu.com/ubuntu hoary-updates main restricted
   
   ## Uncomment the following two lines to add software from the 'universe'
   ## repository.
   ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
   ## team, and may not be under a free licence. Please satisfy yourself as to
   ## your rights to use the software. Also, please note that software in
   ## universe WILL NOT receive any review or updates from the Ubuntu security
   ## team.
   deb https://us.archive.ubuntu.com/ubuntu hoary universe
   deb-src https://us.archive.ubuntu.com/ubuntu hoary universe
   
   deb https://security.ubuntu.com/ubuntu hoary-security main restricted
   deb-src https://security.ubuntu.com/ubuntu hoary-security main restricted
   
   deb https://security.ubuntu.com/ubuntu hoary-security universe
   deb-src https://security.ubuntu.com/ubuntu hoary-security universe
   
   deb https://archive.ubuntu.com/ubuntu hoary multiverse
   deb-src https://archive.ubuntu.com/ubuntu hoary multiverse
   
   ## Backports
   deb https://ubuntu-backports.mirrormax.net/ hoary-backports main universe multiverse restricted
   deb https://ubuntu-backports.mirrormax.net/ hoary-extras main universe multiverse restricted

5. Save the edited file (sample)

6. sudo apt-get update