Articles, notes and random thoughts on Software Development and Technology
I’ve been spending some time working with Docker recently – it’s incredible technology and understandable why it’s getting so much attention for automating reproducible runtimes.
Here’s a quick 5 min overview covering an overview in 5 mins by Vincent Batts, who works at Red Hat on Docker and OpenShift:
Trying to run a shell into a running container (docker exec -it containerid bash) using DockerToolbox/docker-machine on Windows 7 gives this error:
"cannot enable tty mode on non tty input"
(this runs fine on Mac OS X)
This is logged as an issue here. As a workaround, prefix the docker command with winpty, so:
winpty docker exec -it containerid bash
By trial and error I worked this out while building a container running Weblogic Portal 10.3.6 (see my Dockerfiles in the 10.3.6updates branch of my fork of oracle/docker: https://github.com/kevinhooke/weblogic-docker/tree/10.3.6updates).
Even if you do a ‘USER oracle’ followed by a COPY or ADD, the files transferred into the image are still owned by root. This was causing me issues as the WLST script could not read the files owned by root (as you’d expect).
This issue and the justification is described in issue 6119. It doesn’t seem that this will be fixed, it seems like it’s ‘working as designed’.
I’ve been playing on and off with Docker but not frequently enough to remember what I did last time, so here’s a few random unstructured notes (running on Mac OS X):
docker ps : list running containers (this shows a container id which is used in most other commands)
docker ps -a : show all containers including those that are stopped
If you see this:
Get http:///var/run/docker.sock/v1.20/containers/json: dial unix /var/run/docker.sock: no such file or directory. * Are you trying to connect to a TLS-enabled daemon without TLS? * Is your docker daemon up and running?
Then your docker-machine is not running.
Start it up with:
docker-machine start default
After starting, run this to set env vars:
eval "$(docker-machine env default)"
Also see this post, and recommendation to use ‘Docker Quickstart Terminal’ on Mac.
docker images : list created images
docker rm containerid : delete a container
docker rmi imageid : delete an image
Create a new container from an image, in interactive mode, grab the tty, and execute bash in the container (get a command line into the container):
docker run -it imageid bash
Run as background daemon: -d
To start a shell into a running container:
docker exec -it containerid sh (or bash)
Stop a running container:
docker stop containerid
To get the IP address of a container:
docker inspect containername | grep IPAddress
Each running container has it’s own IP address. When a container restarts, it gets a new IP. To access a container running in a docker-machine, find the IP of the docker-machine vm:
docker-machine ls
.. this will list the IP for the VM.
When creating a new container, forward the port in the container to the host with -p, for example for a Weblogic server:
docker run -d –expose:7001 -p 7001:7001 –name=containername imagename