Top 17 Important Docker Commands

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In this post, we will see the top 17 important docker commands that we generally use in Docker environment.

These are the basic Docker commands you need to get started with Docker containers and images.

Install Docker

Before going ahead, take a look at how to install Docker on famous Linux distributions.

READ: How To Install Docker on CentOS 7 / RHEL 7

READ: How To Install Docker on Ubuntu 18.04

READ: How To Install Docker on Ubuntu 16.04

READ: How To Install Docker on Debian 10

READ: How To Install Docker on Debian 9

READ: How To Install Docker on Fedora

Top 10 Docker Commands

Find Docker Version

Let’s check the Docker version installed on the machine.

docker -v

Output:

Docker version 19.03.1, build 74b1e89

You can also use version command to know about Docker components and versions.

docker version

Output:

Client: Docker Engine - Community
 Version:           19.03.1
 API version:       1.40
 Go version:        go1.12.5
 Git commit:        74b1e89
 Built:             Thu Jul 25 21:21:07 2019
 OS/Arch:           linux/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          19.03.1
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.12.5
  Git commit:       74b1e89
  Built:            Thu Jul 25 21:19:36 2019
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.2.6
  GitCommit:        894b81a4b802e4eb2a91d1ce216b8817763c29fb
 runc:
  Version:          1.0.0-rc8
  GitCommit:        425e105d5a03fabd737a126ad93d62a9eeede87f
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683

The info command prints how many containers and images are there along with the information about the operating system, kernel version, CPU, Memory, and hostname.

docker info

Output:

Client:
 Debug Mode: false

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 0
 Server Version: 19.03.1
 Storage Driver: overlay2
  Backing Filesystem: xfs
  Supports d_type: true
  Native Overlay Diff: true
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 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: runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 894b81a4b802e4eb2a91d1ce216b8817763c29fb
 runc version: 425e105d5a03fabd737a126ad93d62a9eeede87f
 init version: fec3683
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 3.10.0-957.21.3.el7.x86_64
 Operating System: CentOS Linux 7 (Core)
 OSType: linux
 Architecture: x86_64
 CPUs: 1
 Total Memory: 1.655GiB
 Name: centos
 ID: RZCG:TOSQ:RL7B:A7FF:ASDB:47GR:KN24:BRKF:KYHZ:5WVV:UTOZ:CDSX
 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

Docker Containers

Create a Docker Container

Though there is a separate command only to create containers, the following command is widely used to create and run containers. It uses the fedora latest docker image to create and start a container.

docker run -dit --name docker-fedora --hostname="fedora" fedora /bin/bash

-d: Run a container in background and print container ID

-i: Run a docker container in interactive mode

-t: Allocates tty terminal which is required to attach to the container

–name: Name of the docker container

–hostname: Set a host to the container

When you issue the command, Docker looks for Fedora image locally, and if it is not found, it will start downloading the Fedora image from Docker registry. Once the image has been downloaded, it will start the container.

Unable to find image 'fedora:latest' locally
latest: Pulling from library/fedora
fd2e8b5b2254: Pull complete 
Digest: sha256:d39a02a0f13c1df3bbcb0ccea4021c53b8e0bfd87f701a5115e18ec089814e70
Status: Downloaded newer image for fedora:latest
8bba0f0ffe3a4553212da5c1bbdca0fac35a210c780f92d0df15fba0feec0a60
You can also create a container with a specific release of an image. For example, to create a Fedora 29 container, you can use fedora:29 as an image name.

List Docker Containers

Check the running containers using the below command.

docker ps

OR

docker container list

Output:

CONTAINER ID        IMAGE               COMMAND             CREATED              STATUS              PORTS               NAMES
8bba0f0ffe3a        fedora              "/bin/bash"         About a minute ago   Up About a minute                       docker-fedora
The -a option will show all containers including stopped ones.

Access Docker Container

The attach command lets you access the running container (docker-fedora). You can see that the container hostname is set to Fedora. Also, run some test commands like “df -hT” to see the mount points details.

docker attach docker-fedora

OR

docker container attach docker-fedora

Output:

[[email protected] ~]# docker attach docker-fedora

[[email protected] /]# df -hT
Filesystem     Type     Size  Used Avail Use% Mounted on
overlay        overlay   10G  2.6G  7.5G  26% /
tmpfs          tmpfs     64M     0   64M   0% /dev
tmpfs          tmpfs    848M     0  848M   0% /sys/fs/cgroup
shm            tmpfs     64M     0   64M   0% /dev/shm
/dev/sda1      xfs       10G  2.6G  7.5G  26% /etc/hosts
tmpfs          tmpfs    848M     0  848M   0% /proc/acpi
tmpfs          tmpfs    848M     0  848M   0% /proc/scsi
tmpfs          tmpfs    848M     0  848M   0% /sys/firmware
To exit from Docker container shell to detach from the container without stopping it, press CTRL+p and followed by CTRL+q.

Check Running Process in Container

The top command shows the running process and its details.

docker top docker-fedora

OR

docker container top docker-fedora

Output:

UID                 PID                 PPID                C                   STIME               TTY                 TIME                CMD
root                3724                3708                0                   07:51               pts/0               00:00:00            /bin/bash

Check Docker Container Statistics

The stats command does live stream of container’s resource usage statistics. The output stats will be similar to Linux’s top command.

docker stats docker-fedora

OR

docker container stats docker-fedora

Output:

CONTAINER ID        NAME                CPU %               MEM USAGE / LIMIT   MEM %               NET I/O             BLOCK I/O           PIDS
8bba0f0ffe3a        docker-fedora       0.00%               620KiB / 1.655GiB   0.04%               656B / 0B           0B / 0B             1

Copy file/folder from Docker Container

The cp command will allow you to copy files/folders from containers to a host system. The following command will copy /root/tobecopied file to /root of a host machine.

docker cp docker-fedora:/root/tobecopied /root/

OR

docker container cp docker-fedora:/root/tobecopied /root/

Stop Docker Container

The kill command sends the SIGTERM signal to kill a running container.

docker kill docker-fedora

OR

docker container kill docker-fedora

You can use docker ps -a command to see the container status.

CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                       PORTS               NAMES
8bba0f0ffe3a        fedora              "/bin/bash"         11 minutes ago      Exited (137) 5 seconds ago                       docker-fedora

Start Docker Container

The start command allows you to start a stopped container.

docker start docker-fedora

OR

docker container start docker-fedora

Restart Docker Container

The restart command allows you to restart a container.

docker restart docker-fedora

OR

docker container restart docker-fedora

Stop Docker Container

The stop command helps you stop a container gracefully

docker stop docker-fedora

OR

docker container stop docker-fedora

Rename Docker Container

The rename command provides an ability to change the name of the container, following command rename the docker-fedora to MyFedora.

docker rename docker-fedora MyFedora

OR

docker container rename docker-fedora MyFedora

Remove Docker Container

The rm command helps you to remove a container. If the container is running, use -f to force remove it.

docker rm MyFedora

OR

docker container rm MyFedora

Docker Images

Search Docker Images

The search command helps you to search for Docker images in the Docker registry, lets search images related to WordPress.

docker search wordpress

Output:

NAME                                     DESCRIPTION                                     STARS               OFFICIAL            AUTOMATED
wordpress                                The WordPress rich content management system…   3066                [OK]                
bitnami/wordpress                        Bitnami Docker Image for WordPress              115                                     [OK]
tutum/wordpress                          Out-of-the-box WordPress docker image           35                                      
appcontainers/wordpress                  Centos/Debian Based Customizable WordPress C…   34                                      [OK]
aveltens/wordpress-backup                Easily backup and restore your WordPress blo…   16                                      [OK]
centurylink/wordpress                    WordPress image with MySQL removed.             14                                      [OK]
arm32v7/wordpress                        The WordPress rich content management system…   10                                      
appsvcorg/wordpress-alpine-php            This is a WordPress Docker image which can …   7                                       
dalareo/wordpress-ldap                   WordPress images with LDAP support automatic…   6                                       [OK]
bitnami/wordpress-nginx                  Bitnami Docker Image for WordPress with NGINX   6                                       [OK]
wodby/wordpress-php                      PHP for WordPress                               4                                       [OK]

Pull Docker Images

The pull command allows you to download Docker images from the registry. By default, it downloads from Docker public registry. But, you can also set Docker to download images from your private registry.

docker pull wordpress

OR

docker image pull bitnami/wordpress

Push Docker Containers

Here is the tutorial on how to push your Docker images to Docker Hub.

List Docker Images

List the available Docker images on the system.

docker images

OR

docker image list

Output:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
bitnami/wordpress   latest              da1f627a8dfd        2 days ago          417MB
wordpress           latest              02126202b6ea        6 days ago          502MB
fedora              latest              ef49352c9c21        10 days ago         246MB
centos              latest              9f38484d220f        5 months ago        202MB
fedora              29                  d09302f77cfc        5 months ago        275MB

Remove Docker Images

You can remove downloaded images using rmi or rm command

docker rmi wordpress

OR

docker image rm wordpress

Output:

Untagged: wordpress:latest
Untagged: [email protected]:fdecb6fc92b04d88419544722ac1679158c12eb8f519b83b0480a6375e823dec
Deleted: sha256:02126202b6ea3d070a0d2e9ded8ea7cc94073525fba5839204fed4f6de62a527
Deleted: sha256:006265425edfa4451bb0b69607ca56bf05576c5ee7dbfd5abe4382ab67175537
Deleted: sha256:fba7a866c3b6a68aacb937015533cc65fa563988e9b58258ff82c48554cfc609
Deleted: sha256:a8222cc6dc755223abf4af699ae1090020858fcaffd431b32a116c9c1cc0609d
Deleted: sha256:a310023bf66eb8e4118deafdf12c800a98d9a77932906d141839bad1963dd96b
Deleted: sha256:87b8b6fb7a45af0d8c4aec69d808a8d43c0e177e89284289f6a02da4aaa617a7
Deleted: sha256:119f74a6f3f65b1a989e6015579e6ada9916ac20128699bc63c20cf71b5fd8db
Deleted: sha256:8976d948286158c42b155e2ba9a9039a23005db8b67ca5471abaac20d54b7dd4

You can also remove all images in a single go which would save you lots of time.

Conclusion

That’s All. I hope you are now able to work with Docker containers and images.

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