Drush install error on Debian

Getting the newest drush (Drupal shell) version via PEAR can give the following error:

Discovering channel pear.drush.org over http:// failed with message: channel-add: Cannot open "http://pear.drush.org/channel.xml" (Cannot download non-http URL "/channel.xml")

Using the following command sequence can solve the problem:

pear upgrade –force Console_Getopt
pear upgrade –force pear
pear upgrade-all
pear channel-discover pear.drush.org
pear channel-discover pear.drush.org
pear install drush/drush

You have to run the channel discovery twice to add the channel. The first try
fails, but the second try succeeds.

The last command then should install drush without any problem.