Using parallel on Ubuntu

Your first try is closest to being correct, but why the :::? If you change ::: to --, it will do what you want.

parallel has a specific, unusual structure to its command line. In the first half, you give it the command you want to run multiple times, and the part of the command line that will be the same every time. In the second half, you give it the parts that will be different each time the command is run. These halves are separated by --. Some experimentation shows that if parallel doesn't find the second half, it doesn't actually run any commands.

It's probably worth re-reading the man page carefully. Man pages have a terse, information-dense style that can take some getting used to. Also try reading some pages for commands you're already familiar with.

By default in ubuntu the parallel behaves as Tollef's implementation (why?). You can check /etc/parallel/config. On the command line you can override this setting and switch it into GNU mode with --gnu. With this switch all examples from the man page should work fine.