Start SSH access for container (helpful to mount container's root volume remotely over sshfs)

install dropbear and sftp in container

bash
if [ -z "$(which dialog)" ]; then sudo apt-get update && sudo apt-get install -y dialog; fi \
&& dialog --menu 'Pick container to instrument' 20 79 20 $(docker ps --format '{{.ID}} {{.Names}}') 2>/tmp/dialog.pick \
&& C="$(cat /tmp/dialog.pick)" \
&& if [ -z "$C" ]; then exit 0; fi \
&& if [ -z "$(docker exec -t ${C} find /etc -name alpine-release)" ]; then
CU='apt-get'; CI='apt-get install -y'; else CU='apk'; CI='apk add'; fi \
&& if [ -z "$(docker exec -t ${C} which dropbear)" ]; then docker exec -t ${C} sh -c "${CU} update && ${CI} dropbear openssh-sftp-server && mkdir /etc/dropbear && dropbearkey -t rsa -f /etc/dropbear/dropbear_rsa_host_key"; fi \
&& docker exec -it ${C} passwd

mount remotely

sshfs -p PORT root@HOST ./MOUNT

start ssh forwarding for container

bash
dialog --menu 'Pick container to access' 20 79 20 $(docker ps --format '{{.ID}} {{.Names}}') 2>/tmp/dialog.pick \
&& C="$(cat /tmp/dialog.pick)" \
&& if [ -z "$C" ]; then exit 0; fi \
&& P1=$(netstat -plnt 2>/dev/null | grep -Po '(222[0-9]{2})' | sort | tail -1) && P2=${P1:-22199} && PORT=$((P2 + 1)) \
&& IP=$((docker exec -t ${C} ip addr) | grep -Po '((172|10)\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})' | grep -v '255\.255') \
&& docker run -l io.rancher.container.network=true -d ${RM} --name ssher-${PORT} -p ${PORT}:${PORT} svendowideit/ambassador ${IP} ${PORT} \
&& docker exec -t ${C} dropbear -p ${PORT}

stop ssh forwarding for container

bash
dialog --menu 'Pick container to lock' 20 79 20 $(docker ps --format '{{.ID}} {{.Names}}') 2>/tmp/dialog.pick \
&& C="$(cat /tmp/dialog.pick)" \
&& if [ -z "$C" ]; then exit 0; fi \
&& PORTCMD=$(docker exec -t ${C} ps ax | grep dropbear | tr -d "\r") \
&& PORT="${PORTCMD##* }" \
&& dialog --inputbox 'Select gateway' 10 10 ssher-${PORT} 2>/tmp/dialog.pick \
&& GWP="$(cat /tmp/dialog.pick)" \
&& if [ -z "$PORT" ]; then exit 0; fi \
&& docker stop ${GWP} && docker rm ${GWP} && docker exec -t ${C} killall dropbear

Works with Docker, local Swarm, local Rancher