Docker command cheat sheet for sysadmin and developers…
Docker is a containerization system which packages and runs the application with its dependencies inside a container. There are several docker commands you must know when working with Docker. This article is all about that.
If you don’t know what Docker is, then you may take this Udemy beginner course.
Finding the version
One of the first things you want to know is how to find the installed docker version.
geekflare@geekflare:/home/geekflare$ docker --version
Docker version 18.09.6, build 481bc77Downloading image
Let’s say you need to pull the docker image from dockerhub (docker repository). The following example of pulling the Apache HTTP server image.
geekflare@geekflare:/home/geekflare$ docker pull httpd
Using default tag: latest
latest: Pulling from library/httpd
f5d23c7fed46: Pull complete
b083c5fd185b: Pull complete
bf5100a89e78: Pull complete
98f47fcaa52f: Pull complete
622a9dd8cfed: Pull complete
Digest: sha256:8bd76c050761610773b484e411612a31f299dbf7273763103edbda82acd73642
Status: Downloaded newer image for httpd:latest
geekflare@geekflare:/home/geekflare$Images
List all the docker images pulled on the system with image details such as TAG/IMAGE ID/SIZE etc.
geekflare@geekflare:/home/geekflare$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
httpd latest ee39f68eb241 2 days ago 154MB
hello-world latest fce289e99eb9 6 months ago 1.84kB
sequenceiq/hadoop-docker 2.7.0 789fa0a3b911 4 years ago 1.76GBRun
Run the docker image mentioned in the command. This command will create a docker container in which the Apache HTTP server will run.
geekflare@geekflare:/home/geekflare$ docker run -it -d httpd
09ca6feb6efc0578951a3e2557ed5855b2edda39a795d9703eb54d975930fe6eWhat’s running?
ps lists all the docker containers are running with container details.
geekflare@geekflare:/home/geekflare$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
09ca6feb6efc httpd "httpd-foreground" 36 seconds ago Up 33 seconds 80/tcp suspicious_bellAs you can see, the Apache server is running in this docker container.
ps -a
List all the docker containers running/exited/stopped with container details.
geekflare@geekflare:/home/geekflare$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
09ca6feb6efc httpd "httpd-foreground" 51 seconds ago Up 49 seconds 80/tcp suspicious_bell
2f6fb3381078 sequenceiq/hadoop-docker:2.7.0 "/etc/bootstrap.sh -d" 2 weeks ago Exited (137) 9 days ago quizzical_raman
9f397feb3a46 sequenceiq/hadoop-docker:2.7.0 "/etc/bootstrap.sh -…" 2 weeks ago Exited (255) 2 weeks ago 2122/tcp, 8030-8033/tcp, 8040/tcp, 8042/tcp, 8088/tcp, 19888/tcp, 49707/tcp, 50010/tcp, 50020/tcp, 50070/tcp, 50075/tcp, 50090/tcp determined_ritchie
9b6343d3b5a0 hello-world "/hello" 2 weeks ago Exited (0) 2 weeks ago peaceful_mcleanexec
Access the docker container and run commands inside the container. I am accessing the apache server container in this example.
geekflare@geekflare:/home/geekflare$ docker exec -it 09ca6feb6efc bash
root@09ca6feb6efc:/usr/local/apache2# ls
bin build cgi-bin conf error htdocs icons include logs modules
root@09ca6feb6efc:/usr/local/apache2#Type exit and press enter to come out of the container.
Removing container
Remove the docker container with container id mentioned in the command.
geekflare@geekflare:/home/geekflare$ docker rm 9b6343d3b5a0
9b6343d3b5a0Run the below command to check if the container got removed or not.
geekflare@geekflare:/home/geekflare$ docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 09ca6feb6efc httpd "httpd-foreground" About a minute ago Up About a minute 80/tcp suspicious_bell 2f6fb3381078 sequenceiq/hadoop-docker:2.7.0 "/etc/bootstrap.sh -d" 2 weeks ago Exited (137) 9 days ago quizzical_raman 9f397feb3a46 sequenceiq/hadoop-docker:2.7.0 "/etc/bootstrap.sh -…" 2 weeks ago Exited (255) 2 weeks ago 2122/tcp, 8030-8033/tcp, 8040/tcp, 8042/tcp, 8088/tcp, 19888/tcp, 49707/tcp, 50010/tcp, 50020/tcp, 50070/tcp, 50075/tcp, 50090/tcp determined_ritchie
Removing image
Remove the docker image with the docker image id mentioned in the command
geekflare@geekflare:/home/geekflare$ docker rmi fce289e99eb9
Untagged: hello-world:latest
Untagged: hello-world@sha256:41a65640635299bab090f783209c1e3a3f11934cf7756b09cb2f1e02147c6ed8
Deleted: sha256:fce289e99eb9bca977dae136fbe2a82b6b7d4c372474c9235adc1741675f587e
Deleted: sha256:af0b15c8625bb1938f1d7b17081031f649fd14e6b233688eea3c5483994a66a3
geekflare@geekflare:/home/geekflare$Restart Docker
Restart the docker container with container id mentioned in the command.
geekflare@geekflare:/home/geekflare$ docker restart 09ca6feb6efc
09ca6feb6efcRun the command below and check the STATUS parameter to verify if the container started recently.
geekflare@geekflare:/home/geekflare$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
09ca6feb6efc httpd "httpd-foreground" 6 minutes ago Up 9 seconds 80/tcp suspicious_bellStopping Docker
Stop a container with container id mentioned in the command.
geekflare@geekflare:/home/geekflare$ docker stop 09ca6feb6efc
09ca6feb6efcRun the below command to check if the container is still running or it has stopped.
geekflare@geekflare:/home/geekflare$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMESStarting Docker
This command in docker starts the docker container with container id mentioned in the command.
geekflare@geekflare:/home/geekflare$ docker start 09ca6feb6efc
09ca6feb6efcRun the command below to check if the container started or not.
geekflare@geekflare:/home/geekflare$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
09ca6feb6efc httpd "httpd-foreground" 8 minutes ago Up 3 seconds 80/tcp suspicious_bellKill
Stop the docker container immediately. Docker stop command stops the container gracefully, that’s the difference between a kill and stop commands.
geekflare@geekflare:/home/geekflare$ docker kill 09ca6feb6efc
09ca6feb6efcRun the below command to see if the container got killed or not.
geekflare@geekflare:/home/geekflare$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMESCommit
Save a new docker image with container id mentioned in the command on the local system. In the example below, geekflare is the username, and httpd_image is the image name.
geekflare@geekflare:/home/geekflare$ docker commit 09ca6feb6efc geekflare/httpd_image
sha256:d1933506f4c1686ab1a1ec601b1a03a17b41decbc21d8acd893db090a09bb31cLogin
Login into docker hub. You will be asked your docker hub credentials to log in.
geekflare@geekflare:/home/geekflare$ docker login
Login with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to https://hub.docker.com to create one.
Username: geekflare
Password:
Configure a credential helper to remove this warning. See
https://docs.docker.com/engine/reference/commandline/login/#credentials-store
Login SucceededPush
Upload a docker image with the image name mentioned in the command on the dockerhub.
geekflare@geekflare:/home/geekflare$ docker push geekflare/httpd_image
The push refers to repository [docker.io/geekflare/httpd_image]
734d9104a6a2: Pushed
635721fc6973: Mounted from library/httpd
bea448567d6c: Mounted from library/httpd
bfaa5f9c3b51: Mounted from library/httpd
9d542ac296cc: Mounted from library/httpd
d8a33133e477: Mounted from library/httpd
latest: digest: sha256:3904662761df9d76ef04ddfa5cfab764b85e3eedaf10071cfbe2bf77254679ac size: 1574Docker network
The following command in docker lists the details of all the network in the cluster.
geekflare@geekflare:/home/geekflare$ docker network ls
NETWORK ID NAME DRIVER SCOPE
85083e766f04 bridge bridge local
f51d1f3379e0 host host local
5e5d9a192c00 none null localThere are several other docker network commands.
geekflare@geekflare:/home/geekflare$ docker network
Usage: docker network COMMAND
Manage networks
Commands:
connect Connect a container to a network
create Create a network
disconnect Disconnect a container from a network
inspect Display detailed information on one or more networks
ls List networks
prune Remove all unused networks
rm Remove one or more networks
Run 'docker network COMMAND --help' for more information on a command.Docker info
Get detailed information about docker installed on the system including the kernel version, number of containers and images, etc.
geekflare@geekflare:/home/geekflare$ docker info
Containers: 3
Running: 1
Paused: 0
Stopped: 2
Images: 3
Server Version: 18.09.6
Storage Driver: overlay2
Backing Filesystem: extfs
Supports d_type: true
Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host 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: bb71b10fd8f58240ca47fbb579b9d1028eea7c84
runc version: 2b18fe1d885ee5083ef9f0838fee39b62d653e30
init version: fec3683
Security Options:
apparmor
seccomp
Profile: default
Kernel Version: 4.18.0-25-generic
Operating System: Ubuntu 18.10
OSType: linux
Architecture: x86_64
CPUs: 1
Total Memory: 4.982GiB
Name: geekflare
ID: RBCP:YGAP:QG6H:B6XH:JCT2:DTI5:AYJA:M44Z:ETRP:6TO6:OPAY:KLNJ
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Username: geekflare
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false
Product License: Community EngineCopying file
Copy a file from a docker container to the local system.
In this example, I am copying httpd.pid file inside a docker container with id 09ca6feb6efc to /home/geekflare/
geekflare@geekflare:/home/geekflare$ sudo docker cp 09ca6feb6efc:/usr/local/apache2/logs/httpd.pid /home/geekflare/
[sudo] password for geekflare:Run the command below to check if the file got copied or not.
geekflare@geekflare:/home/geekflare$ ls
Desktop Documents example examples.desktop httpd.pid nginx_new.yml nginx.ymlChecking history
Shows the history of a docker image with the image name mentioned in the command.
geekflare@geekflare:/home/geekflare$ docker history httpd
IMAGE CREATED CREATED BY SIZE COMMENT
ee39f68eb241 2 days ago /bin/sh -c #(nop) CMD ["httpd-foreground"] 0B
<missing> 2 days ago /bin/sh -c #(nop) EXPOSE 80 0B
<missing> 2 days ago /bin/sh -c #(nop) COPY file:c432ff61c4993ecd… 138B
<missing> 4 days ago /bin/sh -c set -eux; savedAptMark="$(apt-m… 49.1MB
<missing> 4 days ago /bin/sh -c #(nop) ENV HTTPD_PATCHES= 0B
<missing> 4 days ago /bin/sh -c #(nop) ENV HTTPD_SHA256=b4ca9d05… 0B
<missing> 4 days ago /bin/sh -c #(nop) ENV HTTPD_VERSION=2.4.39 0B
<missing> 4 days ago /bin/sh -c set -eux; apt-get update; apt-g… 35.4MB
<missing> 4 days ago /bin/sh -c #(nop) WORKDIR /usr/local/apache2 0B
<missing> 4 days ago /bin/sh -c mkdir -p "$HTTPD_PREFIX" && chow… 0B
<missing> 4 days ago /bin/sh -c #(nop) ENV PATH=/usr/local/apach… 0B
<missing> 4 days ago /bin/sh -c #(nop) ENV HTTPD_PREFIX=/usr/loc… 0B
<missing> 5 days ago /bin/sh -c #(nop) CMD ["bash"] 0B
<missing> 5 days ago /bin/sh -c #(nop) ADD file:71ac26257198ecf6a… 69.2MBChecking logs
Show the logs of the docker container with contained id mentioned in the command.
geekflare@geekflare:/home/geekflare$ docker logs 09ca6feb6efc
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
[Mon Jul 15 14:01:55.400472 2019] [mpm_event:notice] [pid 1:tid 140299791516800] AH00489: Apache/2.4.39 (Unix) configured -- resuming normal operations
[Mon Jul 15 14:01:55.400615 2019] [core:notice] [pid 1:tid 140299791516800] AH00094: Command line: 'httpd -D FOREGROUND'
[Mon Jul 15 14:08:36.798229 2019] [mpm_event:notice] [pid 1:tid 140299791516800] AH00491: caught SIGTERM, shutting down
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
[Mon Jul 15 14:08:38.259870 2019] [mpm_event:notice] [pid 1:tid 139974087980160] AH00489: Apache/2.4.39 (Unix) configured -- resuming normal operations
[Mon Jul 15 14:08:38.260007 2019] [core:notice] [pid 1:tid 139974087980160] AH00094: Command line: 'httpd -D FOREGROUND'
[Mon Jul 15 14:09:01.540647 2019] [mpm_event:notice] [pid 1:tid 139974087980160] AH00491: caught SIGTERM, shutting down
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
[Mon Jul 15 14:10:43.782606 2019] [mpm_event:notice] [pid 1:tid 140281554879616] AH00489: Apache/2.4.39 (Unix) configured -- resuming normal operations
[Mon Jul 15 14:10:43.782737 2019] [core:notice] [pid 1:tid 140281554879616] AH00094: Command line: 'httpd -D FOREGROUND'
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
[Mon Jul 15 14:14:08.270906 2019] [mpm_event:notice] [pid 1:tid 140595254346880] AH00489: Apache/2.4.39 (Unix) configured -- resuming normal operations
[Mon Jul 15 14:14:08.272628 2019] [core:notice] [pid 1:tid 140595254346880] AH00094: Command line: 'httpd -D FOREGROUND'Searching image
Search for a docker image on dockerhub with the name mentioned in the command.
geekflare@geekflare:/home/geekflare$ docker search hadoop
NAME DESCRIPTION STARS OFFICIAL AUTOMATED
sequenceiq/hadoop-docker An easy way to try Hadoop 611 [OK]
uhopper/hadoop Base Hadoop image with dynamic configuration… 98 [OK]
harisekhon/hadoop Apache Hadoop (HDFS + Yarn, tags 2.2 - 2.8) 54 [OK]
bde2020/hadoop-namenode Hadoop namenode of a hadoop cluster 22 [OK]
kiwenlau/hadoop Run Hadoop Cluster in Docker Containers 19
izone/hadoop Hadoop 2.8.5 Ecosystem fully distributed, Ju… 14 [OK]
uhopper/hadoop-namenode Hadoop namenode 9 [OK]
bde2020/hadoop-datanode Hadoop datanode of a hadoop cluster 9 [OK]
singularities/hadoop Apache Hadoop 8 [OK]
uhopper/hadoop-datanode Hadoop datanode 7 [OK]
harisekhon/hadoop-dev Apache Hadoop (HDFS + Yarn) + Dev Tools + Gi… 6 [OK]Updating configuration
Update container configurations. This shows all the update options.
geekflare@geekflare:/home/geekflare$ docker update --help
Usage: docker update [OPTIONS] CONTAINER [CONTAINER...]
Update configuration of one or more containers
Options:
--blkio-weight uint16 Block IO (relative weight), between 10 and 1000, or 0 to disable
(default 0)
--cpu-period int Limit CPU CFS (Completely Fair Scheduler) period
--cpu-quota int Limit CPU CFS (Completely Fair Scheduler) quota
--cpu-rt-period int Limit the CPU real-time period in microseconds
--cpu-rt-runtime int Limit the CPU real-time runtime in microseconds
-c, --cpu-shares int CPU shares (relative weight)
--cpus decimal Number of CPUs
--cpuset-cpus string CPUs in which to allow execution (0-3, 0,1)
--cpuset-mems string MEMs in which to allow execution (0-3, 0,1)
--kernel-memory bytes Kernel memory limit
-m, --memory bytes Memory limit
--memory-reservation bytes Memory soft limit
--memory-swap bytes Swap limit equal to memory plus swap: '-1' to enable unlimited swap
--restart string Restart policy to apply when a container exitsRun the below command to update the CPU configuration of docker container with container id mentioned in the command.
geekflare@geekflare:/home/geekflare$ docker update -c 1 2f6fb3381078
2f6fb3381078Creating volume
Create a volume which docker container will use to store data.
geekflare@geekflare:/home/geekflare$ docker volume create
7e7bc886f69bb24dbdbf19402e31102a25db91bb29c56cca3ea8b0c611fd9ad0Run the below command if the volume got created or not.
geekflare@geekflare:/home/geekflare$ docker volume ls
DRIVER VOLUME NAME
local 7e7bc886f69bb24dbdbf19402e31102a25db91bb29c56cca3ea8b0c611fd9ad0Installing plugin
Install a docker plugin vieux/sshfs with debug environment set to 1.
geekflare@geekflare:/home/geekflare$ docker plugin install vieux/sshfs DEBUG=1
Plugin "vieux/sshfs" is requesting the following privileges:
- network: [host]
- mount: [/var/lib/docker/plugins/]
- mount: []
- device: [/dev/fuse]
- capabilities: [CAP_SYS_ADMIN]
Do you grant the above permissions? [y/N] y
latest: Pulling from vieux/sshfs
52d435ada6a4: Download complete
Digest: sha256:1d3c3e42c12138da5ef7873b97f7f32cf99fb6edde75fa4f0bcf9ed277855811
Status: Downloaded newer image for vieux/sshfs:latest
Installed plugin vieux/sshfs
Run the below command to list the docker plugins.
geekflare@geekflare:/home/geekflare$ docker plugin ls
ID NAME DESCRIPTION ENABLED
2a32d1fb95af vieux/sshfs:latest sshFS plugin for Docker trueLogout
Logging out from dockerhub.
geekflare@geekflare:/home/geekflare$ docker logout
Removing login credentials for https://index.docker.io/v1/Conclusion
I hope you have got a fair understanding of docker commands by now. Try out those commands in your dev or lab environment to practice and learn.
If you are interested in learning Docker and Kubernetes, then check out this online course.