The instructions begin with the user creating a file: “~/whonix_backup” and turn that into the executable backup script. The script then tries to “mkdir ~/whonix_backup” which fails because a file is named that already. You should rename the script.
Please run the Whonix backup script every now and then. Check if the Whonix backup script changed every now and then.
Paste the following content.
sudo apt-get update
sudo apt-get install git git-mediawiki github-backup
mkdir --parents ~/whonix_backup/adrelanos[/code]
Edit: I submitted a change to the wiki.