Ubuntu 用 systemd 了，所以就没有 runlevel 了。

对应的，是一个systemd targets.

   Mapping between runlevels and systemd targets

   ┌─────────┬───────────────────┐

   │Runlevel │ Target            │

   ├─────────┼───────────────────┤

   │0        │ poweroff.target   │

   ├─────────┼───────────────────┤

   │1        │ rescue.target     │

   ├─────────┼───────────────────┤

   │2, 3, 4  │ multi-user.target │

   ├─────────┼───────────────────┤

   │5        │ graphical.target  │

   ├─────────┼───────────────────┤

   │6        │ reboot.target     │

   └─────────┴───────────────────┘

Now, to just change the "runlevels" in 16.04, you can use for eg:

sudo systemctl isolate multi-user.target

To make this the default "runlevel", you can use:

sudo systemctl enable multi-user.target

sudo systemctl set-default multi-user.target

https://askubuntu.com/questions/788323/change-runlevel-on-16-04