Place this in /etc/profile.d/ folder and you can open a shell in a running Docker container

docker-sh.sh

#!/bin/bash

function docker-sh() {
        local __PID=""
        __PID=$(docker inspect --format "{{.State.Pid}}" $1)
        local __EXIT=$?
        if [ $__EXIT -eq 0 ]; then
                nsenter --target $__PID --mount --uts --ipc --net --pid
        fi
}