Docker

Docker, put simply, is a container platform – which solves the issue of running code that is OS agnostic (to an extent) and allows for the application to be freed from it’s underlying OS/kernel dependencies. Simply put, I can run multiple versions of the same application in a container, without having to worry about dependencies and conflicts! In DevOps environment, that is just pure gold! I can have ready to ship code which can be essentially packaged into VM or OS agnostic bits that just work!

Unlike older versions the newer docker Desktop versions need you to register to the https://hub.docker.com portal and also gives you a desktop tray icon. For a MAC, this looks like this

Docker Mac Desktop

Installation is again pretty straightforward. You register at https://hub.docker.com and download the install package. Then doubleclick the dmg file and once that opens with the Docker package, just click and drag the package to the Applications folder and sign in. As simple as that!

Now, to run and ensure Docker has installed fine, you can use the hello-world that is the hello world image from Docker. But before that, just run docker without any arguments to ensure docker fires up correctly

Ayans-MacBook-Pro:~ ayan$ docker

Usage:	docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:
      --config string      Location of client config files (default
                           "/Users/ayan/.docker")
  -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
                           "/Users/ayan/.docker/ca.pem")
      --tlscert string     Path to TLS certificate file (default
                           "/Users/ayan/.docker/cert.pem")
      --tlskey string      Path to TLS key file (default
                           "/Users/ayan/.docker/key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

Management Commands:
  builder     Manage builds
  config      Manage Docker configs
  container   Manage containers
  image       Manage images
  network     Manage networks
  node        Manage Swarm nodes
  plugin      Manage plugins
  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.

Now that you know docker works, check the hello-world and see what comes up

Ayans-MacBook-Pro:~ ayan$ docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
1b930d010525: Pull complete 
Digest: sha256:2557e3c07ed1e38f26e389462d03ed943586f744621577a99efb77324b0fe535
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://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

So that was fun! There’s an additional example that is provided which can be run to check out further functionality

Ayans-MacBook-Pro:~ ayan$ docker run -it ubuntu bash
Unable to find image 'ubuntu:latest' locally
latest: Pulling from library/ubuntu
84ed7d2f608f: Pull complete 
be2bf1c4a48d: Pull complete 
a5bdc6303093: Pull complete 
e9055237d68d: Pull complete 
Digest: sha256:868fd30a0e47b8d8ac485df174795b5e2fe8a6c8f056cc707b232d65b8a1ab68
Status: Downloaded newer image for ubuntu:latest
root@1459d58895b0:/# 
root@1459d58895b0:/# uname -rn
1459d58895b0 4.9.125-linuxkit

Sweet! So we just created an Ubuntu container (basic) and logged in using the root credentials and the bash shell. Let’s run a top to check out the other processes running

#top

top - 16:03:13 up 27 min,  0 users,  load average: 0.03, 0.05, 0.01
Tasks:   2 total,   1 running,   1 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.0 us,  0.3 sy,  0.0 ni, 99.7 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :  2047036 total,   344688 free,   267540 used,  1434808 buff/cache
KiB Swap:  1048572 total,  1048572 free,        0 used.  1620344 avail Mem 

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                                                                               
   17 root      20   0   36612   3108   2624 R   0.3  0.2   0:00.01 top                                                                                   
    1 root      20   0   18504   3472   3052 S   0.0  0.2   0:00.05 bash    

Nice! Now let’s check out the container properties. Open another terminal and check out the docker processes

Ayans-MacBook-Pro:~ ayan$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
1459d58895b0        ubuntu              "bash"              5 minutes ago       Up 5 minutes                            angry_mccarthy

Not bad at all. Now deleting the container. Let’s first list out the total containers in use

Ayans-MacBook-Pro:~ ayan$ docker container ls -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                      PORTS               NAMES
1459d58895b0        ubuntu              "bash"              6 minutes ago       Up 6 minutes                                    angry_mccarthy
8147c23f59a1        hello-world         "/hello"            7 minutes ago       Exited (0) 7 minutes ago                        stoic_shockley
29bf5f2277e9        hello-world         "/hello"            26 minutes ago      Exited (0) 26 minutes ago                       dreamy_payne

You can delete off the stopped containers using the rm command

Ayans-MacBook-Pro:~ ayan$ docker rm 8147c23f59a1 29bf5f2277e9
8147c23f59a1
29bf5f2277e9

Check the list of containers again

Ayans-MacBook-Pro:~ ayan$ docker container ls -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
1459d58895b0        ubuntu              "bash"              9 minutes ago       Up 9 minutes                            angry_mccarthy

Stop all running containers

Ayans-MacBook-Pro:~ ayan$ docker container stop $(docker container ls -aq)
1459d58895b0

Remove/delete all containers

Ayans-MacBook-Pro:~ ayan$ docker container rm $(docker container ls -aq)
1459d58895b0
Ayans-MacBook-Pro:~ ayan$ docker container ls -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
Ayans-MacBook-Pro:~ ayan$ 

Now, though the containers are gone, the images will still be there, right?

Ayans-MacBook-Pro:~ ayan$ docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
hello-world         latest              fce289e99eb9        5 days ago          1.84kB
ubuntu              latest              1d9c17228a9e        8 days ago          86.7MB

To remove the images, we can run the rm command

Ayans-MacBook-Pro:~ ayan$ docker image rm fce289e99eb9 1d9c17228a9e
Untagged: hello-world:latest
Untagged: hello-world@sha256:2557e3c07ed1e38f26e389462d03ed943586f744621577a99efb77324b0fe535
Deleted: sha256:fce289e99eb9bca977dae136fbe2a82b6b7d4c372474c9235adc1741675f587e
Deleted: sha256:af0b15c8625bb1938f1d7b17081031f649fd14e6b233688eea3c5483994a66a3
Untagged: ubuntu:latest
Untagged: ubuntu@sha256:868fd30a0e47b8d8ac485df174795b5e2fe8a6c8f056cc707b232d65b8a1ab68
Deleted: sha256:1d9c17228a9e80a0a23927f24f3cf17d012cf0bb3eae5e3541a8c6987ab9bd5a
Deleted: sha256:3288cd6e6e7d42bcb4a74121b412c42a11f96da52685e42dbf9de6a747a55c6b
Deleted: sha256:b1636589630239bdb9153f95ac564bcd2afd9202aaf8511cbf5a9a37e03daf35
Deleted: sha256:043f492f40c539cfe7cee4cb8aae00ed1d5b19e864fbe6ea35ec92a2333bacc4
Deleted: sha256:2fb7bfc6145d0ad40334f1802707c2e2390bdcfc16ca636d9ed8a56c1101f5b9
Ayans-MacBook-Pro:~ ayan$ 

Check for volumes

Ayans-MacBook-Pro:~ ayan$ docker volume ls
DRIVER              VOLUME NAME

Check for networks

Ayans-MacBook-Pro:~ ayan$ docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
361746435c82        bridge              bridge              local
38babddf71cc        host                host                local
cbaafcdbb22d        none                null                local

For network, I find the prune option easier

Ayans-MacBook-Pro:~ ayan$ docker network prune
WARNING! This will remove all networks not used by at least one container.
Are you sure you want to continue? [y/N] y

Stay tuned for more!

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