on system

su buster

Seems every couple months I have to look this up again, so I'm just going to drop it here. If you're having trouble running privileged commands after su in buster, well... they changed it. For the better, I'm sure, but changed all the same.

The su command in buster is provided by the util-linux source package, instead of the shadow source package, and no longer alters the PATH variable by default. This means that after doing su, your PATH may not contain directories like /sbin, and many system administration commands will fail.

There are several workarounds:

  • Use su - instead; this launches a login shell, which forces PATH to be changed, but also changes everything else including the working directory.
  • Use sudo instead. sudo still runs commands with an altered PATH variable.
  • To get a regular root shell with the correct PATH, you may use sudo -s.
  • To get a login shell as root (equivalent to su -), you may use sudo -i.
  • Put ALWAYS_SET_PATH yes in /etc/default/su (create it) to get an approximation of the old behavior. This is documented in su(1).
echo "ALWAYS_SET_PATH yes" >> /etc/default/su

See: Changes