Alpine

apk command
$ apk update
$ apk upgrade

$ apk add openssh --no-cache
$ apk add openrc --no-cache

Add user|group
$ addgroup -S mygroup 
$ adduser -S myuser -G mygroup 
docker all future commands should run as the myuser user
$ USER myuser 

$ rc-status --list

$ touch /run/openrc/softlevel