DevOps/Docker
Docker is a software available since 2013 that among other features performs operating-system-level virtualization also known as containerization
Features
editDocker offer the following features:
- Package an application and its dependencies in a virtual container that can run on any Linux server (docker images)
- Pull or push docker images to a container repository/container registry (
docker pull
[1],docker push
). By default docker hub but you can specify any other registry.
Installing Docker
editYou can read official Docker documentation about installing Docker on your system: https://docs.docker.com/install/.
On macOS you can follow official documentation https://docs.docker.com/docker-for-mac/install/ which requires to create and account to download installer. You can also try:
brew cask install docker
or try to follow https://pilsniak.com/how-to-install-docker-on-mac-os-using-brew/ instructions:
brew install docker docker-compose docker-machine
(to install docker and docker-compose)brew cask install virtualbox
docker-machine create --driver virtualbox default
docker-machine ls
docker-machine env default
eval $(docker-machine env default)
docker run hello-world
(will pull hello-world image and run it on docker)
On Ubuntu: snap install docker
Binaries
editFollowing binaries will be installed: docker-init
, docker-proxy
, docker
and dockerd
Verifying Docker installation
editOnce installed the Docker daemon, called "dockerd"
should be running.
You can also run docker run hello-world
to verify docker correct installation.
Configuration files
edit- Ubuntu:
/etc/docker/daemon.json
Docker Releases (Docker Engine release notes)
editUse: docker version
[2] to check your version.
You can download Docker CE source code from GitHub[3].
Docker Command Line
editYou can read official docker command line documentation in https://docs.docker.com/engine/reference/commandline/docker/. Before being able to run docker commands you will have to install Docker on your machine.
Some typical task using containers:
Docker verification commands
edit- Verify correct installation:
docker run hello-world
You will see some message similar to this one:
Unable to find image 'hello-world:latest' locally latest: Pulling from library/hello-world ca4f61b1923c: Pull complete Digest: sha256:97ce6fa4b6cdc0790cda65fe7290b74cfebd9fa0c9b8c38e979330d547d22ce1 Status: Downloaded newer image for hello-world:latest Hello from Docker! This message shows that your installation appears to be working correctly. To generate this message, Docker took the following steps: 1. The Docker client contacted the Docker daemon. 2. The Docker daemon pulled the "hello-world" image from the Docker Hub. (amd64) 3. The Docker daemon created a new container from that image which runs the executable that produces the output you are currently reading. 4. The Docker daemon streamed that output to the Docker client, which sent it to your terminal. To try something more ambitious, you can run an Ubuntu container with: $ docker run -it ubuntu bash Share images, automate workflows, and more with a free Docker ID: https://cloud.docker.com/ For more examples and ideas, visit: https://docs.docker.com/engine/userguide/
Docker image and container creation
edit- Create a new docker image base on alpine linux distribution and login into the new container:
docker run -it alpine sh
- Create a new docker image:
docker build
- Create a new docker image by creating a new text file with instructions, usually called
Dockerfile
[4]:docker build -f /path/to/a/Dockerfile .
- Create a new docker image by creating a new text file with instructions, usually called
- Create a container:
docker create
- Generate a mediawiki:1.27 image:
docker build --tag mediawiki:1.27 .
(you can use -t or --tag) - Execute or run a container based on mediawiki:1.27 image:
docker run --name wikiFGA -p 0.0.0.0:9090:80 -d mediawiki:1.27
Docker Container Operation
edit- Start an existing container:
docker start CONTAINER_ID OR CONTAINER_NAME
. See also docker run and differences[5]. - Stop an running container:
docker stop container_id
- Show only running containers:
- Show containers (running or not):
docker ps -a
: https://docs.docker.com/engine/reference/commandline/ps/docker container ls -a
. See alsodocker-compose ps
- Login/Connect into a running container:
docker exec[10] -it <my_container_name> bash
docker exec -it <my_container_name> sh
- Start stopped containers:
docker start $(docker ps -a -q -f status=exited)
- Restart all containers:
docker restart $(docker ps -aq)
previouslydocker restart $(docker ps -q)
-a all -q quiet
[11]
See also: docker compose and docker stack
Docker images management
edit- List created images:
docker images
[13],docker image ls
(both commands seems to perform the same action, note it is image instead of images)
- Images are stored in
docker info | grep "Docker Root Dir"
[14]
docker image rm
[15]. See also:docker rm CONTAINER
Docker Network command line commands
editdocker network ls
docker network inspect
- Deprecated:
docker --link
[16]
Docker resource limitation
edit- Limit container CPU usage to 0.5 cpus:
docker run -it --cpus=".5" docker_image /bin/bash
- Limit memory requires your kernel to have functionality activated, you can check it executing
docker info
. See https://docs.docker.com/install/linux/linux-postinstall/ and docker-compose resource limitation example: DevOps/Docker/docker compose/Version 3 resouces
Docker: Working with remote repositories/registries
editYou will be using mainly the following commands docker login
, docker logout
, docker pull
and docker push
. Docker registry allow to configure notifications. [17]. Docker has a public repository called Docker Hub and cloud providers offer repositories services such as AWS Elastic Container Registry (ECR).
Docker Information
editdocker version
https://docs.docker.com/engine/reference/commandline/version/docker info
https://docs.docker.com/engine/reference/commandline/info/docker stats
docker system info
https://docs.docker.com/v17.12/edge/engine/reference/commandline/system_info/docker system events
https://docs.docker.com/v17.12/edge/engine/reference/commandline/system_events/docker system df
docker top [CONTAINER_NAME or CONTAINER_ID]
https://docs.docker.com/engine/reference/commandline/top/docker inspect CONTAINER_ID|IMAGE_ID
[18] https://docs.docker.com/engine/reference/commandline/inspect/ also available for: container, image, volume, network, node, service, or taskdocker images
,docker images -q
docker image inspect
[19]docker image ls
ordocker image ls --no-trunc
Docker Operation
editdocker run[20] IMAGE|IMAGE_ID
: https://docs.docker.com/engine/reference/run/docker start CONTAINER_ID|CONTAINER_NAME
: https://docs.docker.com/engine/reference/commandline/start/docker stop CONTAINER_ID|CONTAINER_NAME
: https://docs.docker.com/engine/reference/commandline/stop/docker restart CONTAINER_ID|CONTAINER_NAME
: https://docs.docker.com/engine/reference/commandline/restart/
Docker Swarm
editdocker swarm
[21]docker nodes
Maintenance
editdocker system prune -a
remove unused and dangling images. Therefore any images being used in a container, whether they have been exited or currently running, will NOT be affected.[22]
Volumes
editdocker volume
: https://docs.docker.com/engine/reference/commandline/volume/docker volume ls
: https://docs.docker.com/engine/reference/commandline/volume_ls/docker inspect -f 'Template:.Mounts' CONTAINER_NAME
[23]docker volumes prune
Docker logging
editDocker support logging to format or different platforms, such as, json-file, syslog, journald, gelf, fluentd, awslogs, splunk, etwlogs, gcplogs and logentries.[24]
- Configuration is done at docker container start time with command
docker run -it --log-drive LOG_METHOD CONTAINER_ID
- Check method configured in a running container:
docker inspect -f 'Template:.HostConfig.LogConfig.Type' CONTAINER_ID
docker inspect -f 'Template:.HostConfig.LogConfig' CONTAINER_ID
- View logs
docker logs CONTAINER_NAME_OR_ID
(Docker Community Engine only support: local, json-file and journald)docker logs CONTAINER_NAME_OR_ID
2>&1 | grep "STRING_TO_SEARCH" (You will need to redirect outputs to be able to grep output)[25]- See https://docs.docker.com/config/containers/logging/ for more information
Misc
editActivities
edit- Read docker blog: https://blog.docker.com/
- Read Docker Engine release notes (2017) and Docker CE or Docker EE releases.
- Understand the difference between an image and a container, Docker Images vs. Containers: https://stackoverflow.com/a/26960888
- Understand the difference between
docker start
anddocker run
: https://stackoverflow.com/questions/34782678/difference-between-running-and-starting-a-docker-container. See also runC - Read Stackoverflow questions related to docker: https://stackoverflow.com/questions/tagged/docker?tab=Votes
See also
edit- Docker
- Docker Hub official Docker container image registry
- docker compose
- Jenkins X
- Cloud computing/Amazon Web Services/Elastic Container Service (ECS)
- AWS Elastic Container Registry (ECR)
- EKS, Kubernetes and Pods
- DevOps/Container: runC
- Binary repository manager: DevOps/JFrog Artifactory
- containerd
- KVM, multipass
References
edit- ↑ https://docs.docker.com/engine/reference/commandline/pull/
- ↑ https://docs.docker.com/engine/reference/commandline/version/
- ↑ https://github.com/docker/docker-ce/releases
- ↑ https://docs.docker.com/engine/reference/builder/
- ↑ https://stackoverflow.com/questions/34782678/difference-between-running-and-starting-a-docker-container
- ↑ https://docs.docker.com/engine/reference/commandline/container_ls/
- ↑ https://docs.docker.com/engine/reference/commandline/ps/
- ↑ https://www.docker.com/blog/whats-new-in-docker-1-13/
- ↑ https://stackoverflow.com/a/45254760
- ↑ https://docs.docker.com/engine/reference/commandline/exec/
- ↑ https://stackoverflow.com/questions/38221463/command-for-restarting-all-running-docker-containers
- ↑ https://docs.docker.com/config/containers/start-containers-automatically/#use-a-restart-policy
- ↑ https://docs.docker.com/engine/reference/commandline/images/
- ↑ https://stackoverflow.com/questions/19234831/where-are-docker-images-stored-on-the-host-machine
- ↑ https://docs.docker.com/engine/reference/commandline/image_rm/
- ↑ https://docs.docker.com/network/links/
- ↑ https://docs.docker.com/registry/notifications/
- ↑ http://manpages.ubuntu.com/manpages/disco/man1/docker-inspect.1.html
- ↑ https://docs.docker.com/engine/reference/commandline/image_inspect/
- ↑ https://docs.docker.com/engine/reference/run/
- ↑ <https://docs.docker.com/engine/reference/commandline/swarm/
- ↑ https://stackoverflow.com/a/45143234
- ↑ https://stackoverflow.com/questions/30133664/how-do-you-list-volumes-in-docker-containers
- ↑ https://docs.docker.com/config/containers/logging/configure/
- ↑ https://stackoverflow.com/questions/34724980/finding-a-string-in-docker-logs-of-container
- ↑ https://docs.docker.com/engine/reference/commandline/tag/