Docker: Difference between revisions
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* Execute a command in a running container: docker exec -it <container-name> /bin/bash | * Execute a command in a running container: docker exec -it <container-name> /bin/bash | ||
* Obtaining information about CPU and RAM usage: docker stats | * Obtaining information about CPU and RAM usage: docker stats | ||
* Getting stdout logs from a container: docker logs <container-id> | |||
== Container events == | |||
* To get an history of container restarts (starts / stops), use the docker system events --since command. The --since is very important, else it will just stream the new events coming. | |||
* When sending docker stop command, a SIGTERM signal is first issued, then after 15 seconds a SIGKILL signal is sent. This means that a manually issued stop command to a container can produce the same error as a OOM killed container, since in both cases the container process with pid 1 will receive a SIGKILL signal. | |||
== Detaching and attaching == | == Detaching and attaching == | ||
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* This can be used to setup the timezone: | * This can be used to setup the timezone: | ||
ENV TZ=Europe/Moscow | ENV TZ=Europe/Moscow | ||
* ARG directive allows you to provide an argument when building the image. You can provide a default value, and any environment variable that matches exactly the name of the ARG will be passed automatically to the build process. | |||
* You can later refer to an ARG by using $ + the argument name. For instance, $USER. | |||
= Containers = | = Containers = | ||
* A started container is always associated with a command (either one present on the Docker image by default, or another one given on the command-line with docker run). This is the command that will be restarted with docker restart, or ran again after a docker stop / docker start. | * A started container is always associated with a command (either one present on the Docker image by default, or another one given on the command-line with docker run). This is the command that will be restarted with docker restart, or ran again after a docker stop / docker start. | ||
* A container exiting with error code 137 means that the container used too much memory (and was killed by the kernel OOM killer). | |||
* You can limit the memory used by a given container by using the '''--memory=500m''' parameter when starting the container. In that case, if memory runs out, the container is killed/stopped. | |||
* You can also update such parameters on a running container with the docker update command. | |||
* Docker can restart automatically containers; usually this is useful when an error occurs (container out of memory for instance). Use '''--restart on-failure'''. Also note that after a reboot, containers will be automatically restarted when the Docker daemon starts. | |||
= Volumes = | = Volumes = |
Latest revision as of 17:19, 8 March 2024
This is a short tutorial to use Docker.
Basic commands
- List of all containers: docker ps -a
- Remove a container: docker rm <container-id>
- Remove all stopped containers: docker container prune
- List of all images: docker image ls
- Remove an image: docker rmi <image-id>
- Remove all dangling images: docker image prune
- Create a new container (from an image): docker create jatzoo/jrivermc24
- Create and run a new container (from an image): docker run -d --name=jrivermc24--stable --net=host -e VNCPASS=foobar -v /volume1/Public/music:/mnt/media jatzoo/jrivermc24:latest
- Execute a command in a running container: docker exec -it <container-name> /bin/bash
- Obtaining information about CPU and RAM usage: docker stats
- Getting stdout logs from a container: docker logs <container-id>
Container events
- To get an history of container restarts (starts / stops), use the docker system events --since command. The --since is very important, else it will just stream the new events coming.
- When sending docker stop command, a SIGTERM signal is first issued, then after 15 seconds a SIGKILL signal is sent. This means that a manually issued stop command to a container can produce the same error as a OOM killed container, since in both cases the container process with pid 1 will receive a SIGKILL signal.
Detaching and attaching
- Control-P + Control-Q can be used to detach from a running container.
- docker attach command can be used to attach / reattach.
Building an image
- docker build -t app-name .
Dockerfile
- This can be used to setup the timezone:
ENV TZ=Europe/Moscow
- ARG directive allows you to provide an argument when building the image. You can provide a default value, and any environment variable that matches exactly the name of the ARG will be passed automatically to the build process.
- You can later refer to an ARG by using $ + the argument name. For instance, $USER.
Containers
- A started container is always associated with a command (either one present on the Docker image by default, or another one given on the command-line with docker run). This is the command that will be restarted with docker restart, or ran again after a docker stop / docker start.
- A container exiting with error code 137 means that the container used too much memory (and was killed by the kernel OOM killer).
- You can limit the memory used by a given container by using the --memory=500m parameter when starting the container. In that case, if memory runs out, the container is killed/stopped.
- You can also update such parameters on a running container with the docker update command.
- Docker can restart automatically containers; usually this is useful when an error occurs (container out of memory for instance). Use --restart on-failure. Also note that after a reboot, containers will be automatically restarted when the Docker daemon starts.
Volumes
- Volumes with the default local driver can be accessed from the host.
- A volume can be associated only when the container is created, not with a running container.