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DOCKER for Beginners

 Docker is a platform for building, running and shipping applications.


Docker is a tool designed to make it easier to create, deploy, and run applications by using containers. 

Containers:

  • An Isolated Environment for running an application
  • Containers allow a developer to package up an application with all of the parts it needs, such as libraries and other dependencies, and deploy it as one package. 
  • By doing so, thanks to the container, the developer can rest assured that the application will run on any other machine regardless of any customized settings that machine might have that could differ from the machine used for writing and testing the code.
  • The main objective of Containers is Consistent working of an application in all system.
  • In a way, Docker is a bit like a virtual machine. But unlike a virtual machine, rather than creating a whole virtual operating system, Docker allows applications to use the same Linux kernel as the system that they're running on and only requires applications be shipped with things not already running on the host computer. This gives a significant performance boost and reduces the size of the application.


Checking the version

We can check the version of the docker using the following command.

docker version
Client:
 Cloud integration: 1.0.14
 Version:           20.10.6
 API version:       1.41
 Go version:        go1.16.3
 Git commit:        370c289
 Built:             Fri Apr  9 22:49:36 2021
 OS/Arch:           windows/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.6
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.13.15
  Git commit:       8728dd2
  Built:            Fri Apr  9 22:44:56 2021
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.4.4
  GitCommit:        05f951a3781f4f2c1911b05e61c160e9c30eaa8e
 runc:
  Version:          1.0.0-rc93
  GitCommit:        12644e614e25b05da6fd08a38ffa0cfe1903fdec
 docker-init:
  Version:          0.19.0

  GitCommit:        de40ad0
This command give us the elaborate version of all the components of the docker. 

In order to just get the version of the docker alone, we can use the following command.

docker -v

Which gives us a output similar to this,

Docker version 20.10.0, build 7287ab3

docker info

The docker info command displays system wide information.

docker info
Client:
 Context:    default
 Debug Mode: false
 Plugins:
  app: Docker App (Docker Inc., v0.9.1-beta3)
  buildx: Build with BuildKit (Docker Inc., v0.5.1-docker)
  compose: Docker Compose (Docker Inc., 2.0.0-beta.1)
  scan: Docker Scan (Docker Inc., v0.8.0)

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 0
 Server Version: 20.10.6
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 1
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 05f951a3781f4f2c1911b05e61c160e9c30eaa8e
 runc version: 12644e614e25b05da6fd08a38ffa0cfe1903fdec
 init version: de40ad0
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 5.4.72-microsoft-standard-WSL2
 Operating System: Docker Desktop
 OSType: linux
 Architecture: x86_64
 CPUs: 12
 Total Memory: 6.08GiB
 Name: docker-desktop
 ID: XZ2G:J7PC:OMF5:M5WA:PMLW:6MDU:HUE5:T3KJ:5WN3:THN5:XOVI:IFYB
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8

 Live Restore Enabled: false
T

docker help

docker help will give all the commands that can be used in docker.

docker help
Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:
      --config string      Location of client config files (default
                           "C:\\Users\\JARVIS\\.docker")
  -c, --context string     Name of the context to use to connect to the
                           daemon (overrides DOCKER_HOST env var and
                           default context set with "docker context use")
  -D, --debug              Enable debug mode
  -H, --host list          Daemon socket(s) to connect to
  -l, --log-level string   Set the logging level
                           ("debug"|"info"|"warn"|"error"|"fatal")
                           (default "info")
      --tls                Use TLS; implied by --tlsverify
      --tlscacert string   Trust certs signed only by this CA (default
                           "C:\\Users\\JARVIS\\.docker\\ca.pem")
      --tlscert string     Path to TLS certificate file (default
                           "C:\\Users\\JARVIS\\.docker\\cert.pem")
      --tlskey string      Path to TLS key file (default
                           "C:\\Users\\JARVIS\\.docker\\key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

Management Commands:
  app*        Docker App (Docker Inc., v0.9.1-beta3)
  builder     Manage builds
  buildx*     Build with BuildKit (Docker Inc., v0.5.1-docker)
  compose*    Docker Compose (Docker Inc., 2.0.0-beta.1)
  config      Manage Docker configs
  container   Manage containers
  context     Manage contexts
  image       Manage images
  manifest    Manage Docker image manifests and manifest lists
  network     Manage networks
  node        Manage Swarm nodes
  plugin      Manage plugins
  scan*       Docker Scan (Docker Inc., v0.8.0)
  secret      Manage Docker secrets
  service     Manage services
  stack       Manage Docker stacks
  swarm       Manage Swarm
  system      Manage Docker
  trust       Manage trust on Docker images
  volume      Manage volumes

Commands:
  attach      Attach local standard input, output, and error streams to a running container
  build       Build an image from a Dockerfile
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  diff        Inspect changes to files or directories on a container's filesystem
  events      Get real time events from the server
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  history     Show the history of an image
  images      List images
  import      Import the contents from a tarball to create a filesystem image
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  kill        Kill one or more running containers
  load        Load an image from a tar archive or STDIN
  login       Log in to a Docker registry
  logout      Log out from a Docker registry
  logs        Fetch the logs of a container
  pause       Pause all processes within one or more containers
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rename      Rename a container
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Remove one or more images
  run         Run a command in a new container
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  search      Search the Docker Hub for images
  start       Start one or more stopped containers
  stats       Display a live stream of container(s) resource usage statistics
  stop        Stop one or more running containers
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  top         Display the running processes of a container
  unpause     Unpause all processes within one or more containers
  update      Update configuration of one or more containers
  version     Show the Docker version information
  wait        Block until one or more containers stop, then print their exit codes

Run 'docker COMMAND --help' for more information on a command.

To get more help with docker, check out our guides at https://docs.docker.com/go/guides/

The docker help command can also be used to provide the provide usage and options available for any commands.

docker <command> --help
// For example

docker attach --help

The output will be:

Usage:  docker attach [OPTIONS] CONTAINER

Attach local standard input, output, and error streams to a running container

Options:
      --detach-keys string   Override the key sequence for detaching a
                             container
      --no-stdin             Do not attach STDIN
      --sig-proxy            Proxy all received signals to the process
                             (default true)

docker images

This command list all the docker images.

docker images
REPOSITORY   TAG       IMAGE ID       CREATED       SIZE
mysql        latest    c0cdc95609f1   7 hours ago   556MB
ubuntu       latest    7e0aa2d69a15   2 weeks ago   72.7MB
ubuntu       18.04     4eb8f7c43909   2 weeks ago   63.1MB

The command to list all the docker images with only their id.

docker images -q
It will display all the image ids

c0cdc95609f1
7e0aa2d69a15
4eb8f7c43909


docker pull



The docker pull is used to pull an image or repository.

docker pull <image or repository name>
Here is the Output
Using default tag: latest
latest: Pulling from library/ubuntu
345e3491a907: Pull complete
57671312ef6f: Pull complete
5e9250ddb7d0: Pull complete
Digest: sha256:cf31af331f38d1d7158470e095b132acd126a7180a54f263d386da88eb681d93
Status: Downloaded newer image for ubuntu:latest
docker.io/library/ubuntu:latest



docker rmi

The docker rmi is used to remove the image.

docker rmi <imagename>

To remove all the images:

docker rmi $(docker images -aq)



docker inspect

This return low level information about the docker objects.

docker inspect <name>

docker history

It shows the history of the image.

docker history <imagename>





docker run

This runs processes in an isolated container. 
For example,

docker run --name ubuntu1 -it ubuntu /bin/bash



The --name option allows us to provide a name to the image and in the -i and -t allows us to run in interactive and allocate a tty for our process.

docker start

This command is used to start the container.

docker start <container name/id>

docker ps

This command lists all the containers.

docker ps



This command shows only the containers which are running. To list all the containers whether its running or not, the following command can be used.

docker ps -a

docker pause/unpause

This command is used to pause the container.

docker pause <container name/id>



Similarly, to un pause the following command can be used.

docker unpause <container name/id>

docker stop

Stops the specified containers.

docker stop <container name/id>





docker kill

Kills the specified containers.

docker kill <container name/id>


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