sudo-bmitch

Assumptions: remote host is running an older docker version, on Linux, and the user shell is bash.

This script is used to setup a remote docker host running an engine prior to 18.09 to allow remote docker ssh based access. It will upgrade the docker client used by the specific user to 18.09, placing the client binary in $HOME/bin/docker and updating .bashrc to prioritize $HOME/bin over the rest of the path. Once run on the remote host, you can connect to it from another docker 18.09 or newer client over ssh using:

sudo-bmitch

Docker filesystem layers can be tricky to wrap your head around, and even more so how indoes work. Lets take an example and see what happens when you tail a file that exists in the image as part of your container entrypoint:

host$ docker run -d --rm --name test-inode debian tail -f /etc/issue                              
54bbfa8fa1f6751593dcf23103a1cdaec7fde8ffbcb3e31bab466b4f7a3581e7

Now make some changes to the file:

sudo-bmitch

Start with a normal docker ps output:

$ docker ps
CONTAINER ID        IMAGE                            COMMAND                  CREATED             STATUS   PORTS               NAMES
4edf61bfedce        prom/node-exporter:latest        "/bin/node_exporter …"   18 hours ago        Up 18 hours   9100/tcp            prometheus_node-exporter.q44zx0s2lvu1fdduk800e5ini.e68ujezn8rsvsll8epgay2oxi
8ad16badf470        grafana/grafana:latest           "/run.sh"                18 hours ago        Up 18 hours   3000/tcp            prometheus_grafana.1.5qhwvzvlng8ny8utzdajhxsyo
822f8207aee0        prom/prometheus:latest           "/bin/prometheus --c…"   18 hours ago        Up 18 hours   9090/tcp            prometheus_prometheus.1.umq9zg7qpu8cyluwbo4awzhtx
8c3f044d503b        prom/alertmanager:latest         "/bin/alertmanager -…"   18 hours ago        Up 18 hours   9093/tcp            prometheus_alertmanager.1.vtqoaudacac1xlgh0xvvb7j2x
7d32bb10f579        google/cadvisor:latest           "/usr/bin/cadvisor -…"   18

sudo-bmitch

$ cat df.build-arg
FROM busybox

ARG ARGNAME=default
RUN env
RUN echo "ARGNAME=${ARGNAME}"
RUN echo "ARG Prefix=${ARGNAME%_*}" \
 && echo "ARG Suffix=${ARGNAME#*_}"
CMD env

sudo-bmitch

# docker info is great for users to read, but takes work to parse in a script
$ docker info
Containers: 9 
 Running: 4   
 Paused: 0    
 Stopped: 5   
 ...
Swarm: active 
 NodeID: xxx
 Is Manager: true   

sudo-bmitch

$ cat docker-compose.env.yml
version: '2'

services:
  test:
    image: busybox
    command: env
    env_file: ./env.data
    environment:
      - VAL="from compose"