When running any command on the 'open' terminal (actually chroot'd inside of its own container) you have to put { sudo apt clean }because the privileges you have are given to you from... well, google I presume. It took me awhile to catch up on that, I have the same on my chromebook. Also, as Mark Stewart said try run su first and then try it. If you run into a snag there, be it for whatever reason you can use "sudo sudo /bin/bash" which will run you in another instance of bash, effectively making you root. Then run "passwd" to set a new one and exit to return to the normal user mode. Then when you run su the password you just set should work.