docker notes

Docker

docker community installation
  $ curl -fsSL https://get.docker.com -o get-docker.sh
  $ sudo sh get-docker.sh
  
Basic docker commands
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  Run - Start a container
    e.g
      docker run nginx
    Above command will download nginx latest image and run the container. 
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  ps - list containers
    e.g to list all running container. 
      docker ps
    
    output:
    CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS               NAMES
    a0da16a748fc        nginx               "/docker-entrypoint.…"   32 seconds ago      Up 31 seconds       80/tcp              thirsty_benz
    
    ps command show basic information of container like containerId and containerName
    adding -a flag, it will list all conatiner present( running or stoped ) on our host.
    
      docker ps -a
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  STOP - stop a container
    To stop a container we need to pass container ID or container name to the stop command
    e.g 
      docker stop thirsty_benz
    it will stop the container, and you can check it using "docker ps -a" command
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  Rm - Remove a container
    if you want to remove container permanentely, you can use rm command 
    e.g 
      docker rm thirsty_benz
    it will print back the container name if the container removed successfully. 
    you can verify that the container no more listed under "docker ps -a" command
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  images - list existing images on your system 
    e.g
      docker images
      it list all images on your sytem with their sizes
      optput:
      REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
      nginx               latest              08393e824c32        2 days ago          132MB
      hello-world         latest              bf756fb1ae65        7 months ago        13.3kB
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  rmi - remove images
    images eats your disk space[very less than virtual machine ;)]. 
    If the image is no more useful you can remove them using rmi command
    e.g 
      docker rmi nginx
    Note: remember to stop and delete containers which are dependent to successfully delete the image. 
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  Pull - only download images
    It will just pull the image, It will not run the image. 
    e.g 
      docker pull nginx
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  Exec - Execute a command on running container
  e.g
    docker exec <container_name> <your command>
    docker exec mynginx nano /var/www/html/index.html
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  Exec - Execute a command on running container
  e.g
    docker exec <container_name> <your command>
    docker exec mynginx nano /var/www/html/index.html
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  Run - attach and detach
  if you want to run any container in background you can run it in detach mode.
  e.g
    docker run -d nginx
  if you want to attach your console to the perticular container running in detach mode, use attach command 
  e.g
    docker attach <container_id/container_name>
    docker attach mynginx
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  Run - Deep dive
    tag:
      you can tag your docker image to spcifiy the version. 
      if you don't specify tag, it consider it as "latest" tag
      e.g
        docker run nignx:1.0
    stdin:
      "-i" parameter is used to run docker interctive mode. 
      "-t" parameter map your local terminal to container's terminal
      e.g
        docker run -it ubuntu
    port:
      "-p" flag used to map your local free port to docker container post
      e.g
        docker run -p <docker host port>:<docker  nginx
        docker run -p 8080:80 nginx
      so on above example all traffic on 8080 port of docker host routed to container's 80 port.
    volume:
      container destroy it's container as soon as it get terminated. but in many case we need to persist the data. 
      e.g
      when we running mysql, we need to persist the data. so we can map a directory of docker host to a directory inside
      the docker container. 
      
      docker run -v /opt/datadir:/var/lib/mysql mysql
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  Inspect container
    docker inspect command used when we want to get detaies related to container
    e.g
      docker inspect <container_name/container_id>
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  Environment varialbe
    many docker container require docker environment varialbe
    e.g
      docker run -e MYSQL_ROOT_PASSWORD=password mysql:5.7