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Docker Command

Docker Run/Pull/Stop/Delete

  • docker run --name "name_of_container" -d "container_image_name"
    • -d in daemon mode (run behind the process)
  • docker run --name "name_of_container" -d -t "container_image_name" (to create the container and keep it up/running behind)
  • docker ps (list of running docker containers/to identify a running container in docker)
  • docker ps -a (list of all docker containers, that are not discarded yet)
  • docker inspect (runtime information of container; listing metadata about a running or stopped container in json format)
  • docker inspect - '{{.NetworkSettings.IPAddress}}' CONTIANER_NAME/CONTAINER_ID (retrieve only ip address of a running container)
  • docker inspect - '{{.NetworkSettings.Port}}' CONTIANER_NAME/CONTAINER_ID (retrieve only port of a running container)
  • docker stop CONTIANER_NAME/CONTAINER_ID (stopping a running container)
  • docker kill CONTIANER_NAME/CONTAINER_ID (stopping a running container forcefully)
  • docker kill -s SIGKILL CONTIANER_NAME/CONTAINER_ID
  • docker start CONTAINER_NAME/CONTAINER_ID (to restart a stopped container)
  • docker start -ai CONTAINER_NAME/CONTAINER_ID (to restart a stopped container and output of the command)
  • docker restart CONTIANER_NAME/CONTAINER_ID (my-httpd-container)
  • docker rmi IMAGE_NAME/IMAGE_ID (delete a container image from machine/cached)`
  • docker rm CONTIANER_NAME/CONTAINER_ID (delete a container not the image)
  • docker rm $(docker ps -aq) (deleting all container, -q returns only Id of containers)
  • docker stop $(docker ps -q)
  • docker exec -it CONTAINER_NAME/CONTAINER_ID bash (exec: to enter the running docker container; it: interactive terminal; to enter the running docker container/access the running container bash shell)
    • Example: docker exec -it mysql bash
  • docker logs CONTIANER_NAME/CONTAINER_ID (to see the console log of the container)
    • Example: docker logs mysql

Manipulating Container Images

  • To share image accross server, team , platform
    • Docker image registry(ies)
    • docker.io
    • registry.access.redhat.com

Saving and Loading Images

  • docker save
    • docker save [-o FILENAME] IMAGE_NAME[:TAG] (-o is optional; generated image in standard output as binary data)
    • Example: docker save -o mysql.tar.registry.redhat.com/rhsch/mysql-56-rhel17
  • docker load
    • docker load [-i FILENAME]
    • Example: docker load -i mysql.tar
    • (docker gzip [-i FILENAME])
    • (docker gunzip) (before importing it to te daemon's caches history)

Publishing Image to a Registry

  • docker tag
    • docker tag IMAGE[:TAG][REGITRY_HOST/][USER_NAME/]NAME[:TAG]
    • Example: docker tag nginx nginx
    • docker tag mysql-custom devops/mysql (to tag an image) (The mysql-custom option is the image name that is stored in the docker daemon's cache)
    • docker tag mysql-custom devops/mysql:snapshots (to use a different tag name)
    • To associate multiple tags with a single image, use docker tag command
    • Tags can be removed from the daemon using rmi
      • docker rmi devops/mysql:snapshot
    • Because multiple tags can point to the same image, to remove an image referred to by multiple tags, each tag should be individually removed first

Push an Image to the Registry

  • docker push
    • docker push NAME[:TAG]
    • Example: docker push nginx
  • Image name syntax
    • [registry_uri/][user_name/]image_name[:tag] (tag normally version number)

To delete from docker cache of any Image that is downloaded to docker cached

  • docker rmi [OPTIONS] IMAGE [IMAGE..] (Options: --force or -f to delete forcefully)
  • docker rmi $(docker images -q) (deleting all images)

Modifying Images

  • docker diff
    • docker diff CONTAINER
    • Example: docker diff mysql-basic
  • docker commit
    • docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]
    • Example: docker mysql-basic.mysql-custom
    • Options available for docker commit
      • --author=" "
      • --message=" "
    • docker commit mysql-basic mysql-cutom (to commit the changes to another image, run this command) !?

To Create a new image, there are two approaches

  • Using a running container
    • docker run -p host_port:container_port --name container_name image_name
  • Using a Dockerfile
    • docker build -t DOCKER_IMAGE_NAME /path/DOCKER_FILE
  • To mount volume within host and container
    • docker run -p host_port:container_port --name container_name -v /path/folder:/path/in_container image_name
    • Example: docker run -p 81:80 --name localdocker -v /home/user/Docker/src:/var/www/html testdocker

Docker Inspect

  • docker inspect -f=='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' container_name|ID
  • docker inspect -f=='{{range .NetworkSettings.Networks}}{{.MacAddress}}{{end}}' container_name|ID
  • docker inspect -f=='{{.LogPath}}' container_name|ID
  • docker inspect --format='{{.Config.Image}}' container_name|ID

Docker Log

  • docker logs --details container_name|ID
  • docker logs --tail all container_name|ID
  • docker logs -f container_name|ID

Run Docker in Remote

  • docker -H=remote-docker-engine:PORT_NO
  • example - docker -H=10.123.2.1:2375 run --name -d lb_nginx nginix:v1

Run with resource limit

  • docker run --cpus=.5 --name ubuntu_container -d ubuntu [not more than 50% cpus]
  • docker run --memory=100m --name ubuntu_container -d ubuntu [use 100 mb]

Docker Volume

  • Image Layers - Read Only; Container Layer - Read Write
  • COPY-ON-WRITE - Write/Update of a file can only apply on Container Layer or Read Write Layer.
  • docker volume create data_volume . It will create data_volume directory under /var/lib/docker/volumes folder. Then we can run to mount with container;
    • docker run -v data_volument:/var/lib/mysql --name -d mysql_db mysql
  • Two Types of Volume
    • Volume Mount - mounts a volumn creating by docker & mounts the directory in the /var/lib/docker/volume directory.
    • Bind Mount - mounts the directory in any location in the host machine.
  • Using -v is old way. The new way is to use --mount option which is more verbose.
  • Example: docker run --mount type=bind, source=/data/mysql, target=/var/lib/mysql -d --name mysql_db mysql
  • Storage Drivers
    • Docker common storage drivers - AUFS, ZFS, BTRFS, Device Mapper, Overlay, Overlay2
  • Volume Drivers (Volumes are handled by Volume Driver Plugins)
    • The default Vuloumn Driver Plugin is Local. The Local Volume Driver Plugin helps creating a volumn in Docker Host Machine and store the data under /var/lib/docker/volumes directory.
    • Volume Driver Provider: Local, Azure File Storage, Convoy, DigitalOcean Block Storage, Flocker, GCE-Docker, GlusterFS, NetApp, PortWox, RexRay etc.
      • Example: docker run -it --name mysql-con --volume-driver rexray/ebs --mount src=ebs-vol, target=/var/lib/mysql mysql

Container Storage Interface (CSI)

  • Container Runtime - rkt, cri-o.
  • Container Runtime Interface(CRI) - rkt, cri-o
  • Container Network Interface(CNI) - weaveworks, flannel, cilium
  • Container Storage Interface(CSI) - portwox, Amazon EBS, GlusterFS
  • CSI is not built on K8S specific standard rather built on general storage standard that can support any storage vendor.
  • Kubernetes, CloudFoundry & Mesos are on board with CSI.
  • Set of RPC
    • CreateVolume
    • DeleteVolume
    • ControllerPublishVolume

Docker Network

  • Bridge, None, Host
  • docker run ubuntu --network=none or docker run ubuntu --network=host. Default is bridge
  • Bridge network range start from 172.17.0.0
  • By default docker create one internal network. We can create as well internal network as - docker network create --driver=bridge --subnet=182.18.0.0/16 custom-isolated-network
  • docker network ls
  • docker inspect container_id
  • docker container DNS always run at 127.0.0.11 port number.
  • docker network create wp-mysql-network --driver=bridge --subnet=182.18.0.1/24 --gateway=182.18.0.1
  • docker network ls
  • docker inspect alpine-1 | grep -i network
  • docker network inspect bridge
  • docker run -d --name alpine-2 --network none alpine
  • docker network create wp-mysql-network --driver=bridge --subnet=182.18.0.1/24 --gateway=182.18.0.1
  • docker run -d --name mysql-db -e MYSQL_ROOT_PASSWORD=db_pass123 --network wp-mysql-network mysql
  • docker network inspect wp-mysql-network
  • docker run -d --name webapp -e DB_Host=mysql-db --network wp-mysql-network kodekloud/simple-webapp-mysql
  • docker network inspect wp-mysql-network

Docker Registry

  • Docker public DNS is Docker Hub -> docker.io
  • image: Registry/User_Account/Image_Or_Repository -> docker.io/ngnix/nginx
  • Run from private registry: docker run private-registry.io/apps/internal-app
  • Docker registry is itself an application and availabe as an image and can be deployed as container in local.
  • Deploy docker registry in locally - docker run -d --name local-registry -p 5000:5000 registry:2
  • docker image tag my-image localhost:5000/my-image
  • Push image in local registry - docker push localhost:5000/my-image
  • Pull image from local registry - docker pull localhost:5000/my-image
  • Pull image from another host registry - docker pull 192.168.56.100:5000/my-image

Limiting Memory & CPU Usage

Follow the command docker info To Change this - WARNING: No swap limit support to Configure/Enable from vi /etc/default/grub

  • GRUB_CMDLINE_LINUX="cgroup_enable=memory swapaccount=0" from GRUB_CMDLINE_LINUX="cgroup_enable=memory swapaccount=1"

  • sudo update-grub

  • docker stats or docker stats container_name or docker stats container_id

  • Limiting Memory Usage

    • Hard Limit
      • docker run --name lb_nginx -d -p 8081:80 --memory="256m" nginx
    • Soft Limit
      • docker run --name lb_nginx -d -p 8081:80 --memory-reservation="256m" nginx
      • docker run --name lb_nginx -d -p 8081:80 --memory="256m"--memory-reservation="512m" nginx
    • Using Memory Swap (To limit a container's use of memory swap to disk use)
      • docker run --name lb_nginx -d -p 8081:80 --memory="256m" --memory-swap="512m" nginx

  • Limiting CPU Usage

    • docker run --name lb_nginx -d -p 8081:80 --cpus=".5" nginx
    • To limit a container’s CPU shares use --cpus-shares
      • docker run --name lb_nginx -d -p 8081:80 --cpus-shares="512" nginx

Security

  • /usr/include/linux/capabilites.h
  • docker run --cap-add NET_BIND ubuntu
  • docker run --cap-drop KILL ubuntu
  • docker run --privileged ubuntu

Create a docker-compose.yml file under the path /root/wordpress. Once done, run a docker-compose up.

version: '3.0'
services:
  db:
    environment:
      POSTGRES_PASSWORD: mysecretpassword
    image: postgres
  wordpress:
    image: wordpress
    links:
    - db
    ports:
    - 8085:80
  • docker-compose -f docker-compose.yaml config
  • docker-compose up
  • Create a container with volume
  • docker run --name mysql-db -e MYSQL_ROOT_PASSWORD=db_pass123 -v /opt/data:/var/lib/mysql -d mysql
  • To view the data in mysql-db container
  • docker exec mysql-db mysql -pdb_pass123 -e 'use foo; select * from myTable'
  • docker network ls
  • What is the subnet configured on bridge network?
  • docker inspect bridge
  • Run a container named alpine-2 using the alpine image and attach it to the none network.
  • docker run --name alpine-2 --network=none -d alpine
  • Create a new network named wp-mysql-network using the bridge driver. Allocate subnet 182.18.0.1/24. Configure Gateway 182.18.0.1
  • docker network create wp-mysql-network --subnet=182.18.0.1/24 --gateway=182.18.0.1
  • Deploy a mysql database using the mysql:5.6 image and name it mysql-db. Attach it to the newly created network wp-mysql-network. Set the database password to use db_pass123. The environment variable to set is MYSQL_ROOT_PASSWORD
  • docker run --name mysql-db -e MYSQL_ROOT_PASSWORD=db_pass123 --network=wp-mysql-network -d mysql:5.6
  • Deploy a web application named webapp, using image kodekloud/simple-webapp-mysql. Expose port to 38080 on the host. The application takes an environment variable DB_Host that has the hostname of the mysql database. Make sure to attach it to the newly created network wp-mysql-network
  • docker run --network=wp-mysql-network -e DB_Host=mysql-db -e DB_Password=db_pass123 -p 38080:8080 --name webapp --link mysql-db:mysql-db -d kodekloud/simple-webapp-mysql