Docker & Gentoo Linux & su could not open session

kamil@kamil-elitebook:~$ docker run -ti oraclelinux:6 /bin/bash
[root@bac7e6cd1aad /]# su - oracle
could not open session

2 hours of googling later:

kamil@kamil-elitebook:~$ docker run --privileged -ti oraclelinux:6 /bin/bash
[root@2f676eeb3b7a /]# su - oracle
[oracle@2f676eeb3b7a ~]$