The first of the two errors has nothing to do with the package itself - packages need root permisions to be managed, which is what exactly the error is telling

The first of the two errors has nothing to do with the package itself - packages need root permisions to be managed, which is what exactly the error is telling you: E: Unable to lock the administration directory (/var/lib/dpkg/), are you root? ^^^^^^^^^^^^^ In your case, you didn't prepend `sudo`. Regarding the second, which is instead the core of the problem, see the man page (http://manpages.ubuntu.com/manpages/xenial/man1/purge-old-kernels.1.html http://manpages.ubuntu.com/manpages/xenial/man1/purge-old-ke...): Provided by: byobu_5.106-0ubuntu1_all bug Therefore the correct (and full) command is: sudo apt-get install byobu As pointed out in another comment, such package is arguably a poor placement for this type of utility.