docker-notes

attaching to a stopped (?) container:

docker start <unique id>

docker attach <unique id>

After that second command:tab, your terminal prompt should've changed.

Running a new container:

docker run -it ubuntu /bin/bash

This will run the container in interactive mode and start a bash prompt.

Pulling an image so you can use it later/again from the main repo

docker pull -a fedora

the -a flag will pull all versions

Look at the currently installed containers

docker ps -a

-a will show us all the installed ones. Without it, it will just show the running ones.

Exit from a tty: ctrl+p then ctrl+c but leave it running

docker images shows all downloaded images.

Making and exporting an image

docker commit <id> <image name> will create your own image.

docker save -o <dest.tar> <image name> will save the image (large).

docker load -e <src.tar> will load an image into your docker

docker run -it <loaded image name> /bin/bash will open an interactive bash like we've seen before

Container workflows

When running interactively, you can detach from the container by ctrl+p ctrl+c. This will leave it running in the background.

docker stop <container id> sends SIGTERM to PID1

docker start <container id> starts up the last running process for that container

docker attach <container id> puts you back in interactive mode

docker restart <container id> SIGTERMs PID1 and starts it back up, I think.

Deleting Containers

docker info shows number of images and containers

docker rm <container id> removes container

Container information

docker top <container id> shows all running processes

docker inspect <container id> shows json information about a running container.

Connecting to container

docker inspect <container id> | grep Pid gives us the host's pid for a container

nsenter -m -u -n -p -i -t <pid> /bin/bash changes namespaces

Namespaces: mount, uts, network, process, ipc of -target pid.

docker-enter <container id>

docker exec -it <container id> /bin/bash: recommended