Originally Posted by Fred Caro
on a runing pc I can change to runlevel 1 on Debian but not on Ubuntu or Mint, why is this?
Because Debian uses System V Init and Ubuntu and Mint use Upstart, which don't have the runlevel facility. Debian will be switching to systemd in Jessie (Which means Debian Sid and Testing are likely to be switched over to it very soon.). Systemd also has no "runlevels" per se but something called "targets" which are more fine-grained and easier to define. But neither upstart or systemd have an "init <runlevel>" command.
As a result of the impending Debian change, Ubuntu and likely Mint are going to jump to systemd as well, as Ubuntu's package ecosystem is pretty much just a stabilized Debian Sid snapshot with some Canonical-driven junk mixed in.
Just run the "reboot" (Same as init 6.) or "poweroff" (Same as init 0) commands via root or sudo. They're commands independent of init implementation and will work with SysVInit, Upstart, and systemd no problem. Refer to Upstart or systemd documentation to figure how to get into "single" mode as that's a heavily implementation-reliant runlevel.