Usage: RUN command (shell form, the command is run in a shell, which by default is /bin/sh -c on Linux or cmd /S /C on Windows) RUN ', ', ' (exec form) Information: The exec form makes it possible to avoid shell string munging, and to RUN commands using a base image that does not contain the specified shell executable.; The default shell for the shell form. The ultimate Docker Commands cheat sheet. Find everything you need to in this handy reference for the most common Docker commands. ENTRYPOINT 'executable', 'param1', 'param2' ENTRYPOINT command param1 param2 Configures a container that will run as an executable. ENTRYPOINT exec top -b This will use shell processing to substitute shell variables, and will ignore any CMD or docker run command line arguments. Metadata LABEL version='1.0'. Docker Commands — The Ultimate Cheat Sheet by@nickparsons Docker Commands — The Ultimate Cheat Sheet Originally published by Nick Parsons on August 21st 2018 40,409 reads.

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Instructions

Usage:

  • FROM <image>
  • FROM <image>:<tag>
  • FROM <image>@<digest>

Information:

  • FROM must be the first non-comment instruction in the Dockerfile.
  • FROM can appear multiple times within a single Dockerfile in order to create multiple images. Simply make a note of the last image ID output by the commit before each new FROM command.
  • The tag or digest values are optional. If you omit either of them, the builder assumes a latest by default. The builder returns an error if it cannot match the tag value.

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Usage:

  • MAINTAINER <name>

The MAINTAINER instruction allows you to set the Author field of the generated images.

Usage:

  • RUN <command> (shell form, the command is run in a shell, which by default is /bin/sh -c on Linux or cmd /S /C on Windows)
  • RUN ['<executable>', '<param1>', '<param2>'] (exec form)

Information:

  • The exec form makes it possible to avoid shell string munging, and to RUN commands using a base image that does not contain the specified shell executable.
  • The default shell for the shell form can be changed using the SHELL command.
  • Normal shell processing does not occur when using the exec form. For example, RUN ['echo', '$HOME'] will not do variable substitution on $HOME.

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Usage:

  • CMD ['<executable>','<param1>','<param2>'] (exec form, this is the preferred form)
  • CMD ['<param1>','<param2>'] (as default parameters to ENTRYPOINT)
  • CMD <command> <param1> <param2> (shell form)

Information:

  • The main purpose of a CMD is to provide defaults for an executing container. These defaults can include an executable, or they can omit the executable, in which case you must specify an ENTRYPOINT instruction as well.
  • There can only be one CMD instruction in a Dockerfile. If you list more than one CMD then only the last CMD will take effect.
  • If CMD is used to provide default arguments for the ENTRYPOINT instruction, both the CMD and ENTRYPOINT instructions should be specified with the JSON array format.
  • If the user specifies arguments to docker run then they will override the default specified in CMD.
  • Normal shell processing does not occur when using the exec form. For example, CMD ['echo', '$HOME'] will not do variable substitution on $HOME.

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Usage:

  • LABEL <key>=<value> [<key>=<value> ..]

Information:

  • The LABEL instruction adds metadata to an image.
  • To include spaces within a LABEL value, use quotes and backslashes as you would in command-line parsing.
  • Labels are additive including LABELs in FROM images.
  • If Docker encounters a label/key that already exists, the new value overrides any previous labels with identical keys.
  • To view an image’s labels, use the docker inspect command. They will be under the 'Labels' JSON attribute.

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Usage:

  • EXPOSE <port> [<port> ..]

Information:

  • Informs Docker that the container listens on the specified network port(s) at runtime.
  • EXPOSE does not make the ports of the container accessible to the host.

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Usage:

  • ENV <key> <value>
  • ENV <key>=<value> [<key>=<value> ..]

Information:

  • The ENV instruction sets the environment variable <key> to the value <value>.
  • The value will be in the environment of all “descendant” Dockerfile commands and can be replaced inline as well.
  • The environment variables set using ENV will persist when a container is run from the resulting image.
  • The first form will set a single variable to a value with the entire string after the first space being treated as the <value> - including characters such as spaces and quotes.

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Usage:

  • ADD <src> [<src> ..] <dest>
  • ADD ['<src>', .. '<dest>'] (this form is required for paths containing whitespace)

Information:

  • Copies new files, directories, or remote file URLs from <src> and adds them to the filesystem of the image at the path <dest>.
  • <src> may contain wildcards and matching will be done using Go’s filepath.Match rules.
  • If <src> is a file or directory, then they must be relative to the source directory that is being built (the context of the build).
  • <dest> is an absolute path, or a path relative to WORKDIR.
  • If <dest> doesn’t exist, it is created along with all missing directories in its path.

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Usage:

  • COPY <src> [<src> ..] <dest>
  • COPY ['<src>', .. '<dest>'] (this form is required for paths containing whitespace)

Information:

  • Copies new files or directories from <src> and adds them to the filesystem of the image at the path <dest>.
  • <src> may contain wildcards and matching will be done using Go’s filepath.Match rules.
  • <src> must be relative to the source directory that is being built (the context of the build).
  • <dest> is an absolute path, or a path relative to WORKDIR.
  • If <dest> doesn’t exist, it is created along with all missing directories in its path.

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Usage:

  • ENTRYPOINT ['<executable>', '<param1>', '<param2>'] (exec form, preferred)
  • ENTRYPOINT <command> <param1> <param2> (shell form)

Information:

  • Allows you to configure a container that will run as an executable.
  • Command line arguments to docker run <image> will be appended after all elements in an exec form ENTRYPOINT and will override all elements specified using CMD.
  • The shell form prevents any CMD or run command line arguments from being used, but the ENTRYPOINT will start via the shell. This means the executable will not be PID 1 nor will it receive UNIX signals. Prepend exec to get around this drawback.
  • Only the last ENTRYPOINT instruction in the Dockerfile will have an effect.

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Usage:

  • VOLUME ['<path>', ..]
  • VOLUME <path> [<path> ..]

Creates a mount point with the specified name and marks it as holding externally mounted volumes from native host or other containers.

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Usage:

  • USER <username UID>

The USER instruction sets the user name or UID to use when running the image and for any RUN, CMD and ENTRYPOINT instructions that follow it in the Dockerfile.

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Usage:

  • WORKDIR </path/to/workdir>

Information:

  • Sets the working directory for any RUN, CMD, ENTRYPOINT, COPY, and ADD instructions that follow it.
  • It can be used multiple times in the one Dockerfile. If a relative path is provided, it will be relative to the path of the previous WORKDIR instruction.

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Usage:

  • ARG <name>[=<default value>]

Information:

  • Defines a variable that users can pass at build-time to the builder with the docker build command using the --build-arg <varname>=<value> flag.
  • Multiple variables may be defined by specifying ARG multiple times.
  • It is not recommended to use build-time variables for passing secrets like github keys, user credentials, etc. Build-time variable values are visible to any user of the image with the docker history command.
  • Environment variables defined using the ENV instruction always override an ARG instruction of the same name.
  • Docker has a set of predefined ARG variables that you can use without a corresponding ARG instruction in the Dockerfile.
    • HTTP_PROXY and http_proxy
    • HTTPS_PROXY and https_proxy
    • FTP_PROXY and ftp_proxy
    • NO_PROXY and no_proxy

Usage:

  • ONBUILD <Dockerfile INSTRUCTION>

Information:

  • Adds to the image a trigger instruction to be executed at a later time, when the image is used as the base for another build. The trigger will be executed in the context of the downstream build, as if it had been inserted immediately after the FROM instruction in the downstream Dockerfile.
  • Any build instruction can be registered as a trigger.
  • Triggers are inherited by the 'child' build only. In other words, they are not inherited by 'grand-children' builds.
  • The ONBUILD instruction may not trigger FROM, MAINTAINER, or ONBUILD instructions.

Reference-Best Practices

Usage:

  • STOPSIGNAL <signal>

The STOPSIGNAL instruction sets the system call signal that will be sent to the container to exit. This signal can be a valid unsigned number that matches a position in the kernel’s syscall table, for instance 9, or a signal name in the format SIGNAME, for instance SIGKILL.

Usage:

  • HEALTHCHECK [<options>] CMD <command> (check container health by running a command inside the container)
  • HEALTHCHECK NONE (disable any healthcheck inherited from the base image)

Information:

  • Tells Docker how to test a container to check that it is still working
  • Whenever a health check passes, it becomes healthy. After a certain number of consecutive failures, it becomes unhealthy.
  • The <options> that can appear are..
    • --interval=<duration> (default: 30s)
    • --timeout=<duration> (default: 30s)
    • --retries=<number> (default: 3)
  • The health check will first run interval seconds after the container is started, and then again interval seconds after each previous check completes. If a single run of the check takes longer than timeout seconds then the check is considered to have failed. It takes retries consecutive failures of the health check for the container to be considered unhealthy.
  • There can only be one HEALTHCHECK instruction in a Dockerfile. If you list more than one then only the last HEALTHCHECK will take effect.
  • <command> can be either a shell command or an exec JSON array.
  • The command's exit status indicates the health status of the container.
    • 0: success - the container is healthy and ready for use
    • 1: unhealthy - the container is not working correctly
    • 2: reserved - do not use this exit code
  • The first 4096 bytes of stdout and stderr from the <command> are stored and can be queried with docker inspect.
  • When the health status of a container changes, a health_status event is generated with the new status.

Usage:

  • SHELL ['<executable>', '<param1>', '<param2>']

Information:

  • Allows the default shell used for the shell form of commands to be overridden.
  • Each SHELL instruction overrides all previous SHELL instructions, and affects all subsequent instructions.
  • Allows an alternate shell be used such as zsh, csh, tcsh, powershell, and others.

Notes

  • Based on the information from Dockerfile reference and Docker file best practices.
  • Converted by halprin.

Docker swarm cheat sheet. List of all commands to create, run, manage container cluster environment, Docker Swarm!

Docker swarm is a cluster environment for Docker containers. Swarm is created with a number of machines running docker daemons. Collectively they are managed by one master node to run clustered environment for containers!

In this article, we are listing out all the currently available docker swarm commands in a very short overview. This is a cheat sheet you can glance through to brush or your swarm knowledge or quick reference for any swarm management command. We are covering most used or useful switches with the below commands. There are more switches available for each command and you can get them with --help

Read all docker or containerization related articles here from KernelTalk’s archives.

Docker swarm commands for swarm management

This set of command is used mainly to start, manage the swarm cluster as a whole. For node management, within the cluster, we have a different set of commands following this section.

Docker Commands The Ultimate Cheat Sheet
  • docker swarm init : Initiate swam cluster
    • –advertise-addr: Advertised address on which swarm lives
    • –autolock: Locks manager and display key which will be needed to unlock stopped manager
    • –force-new-cluster: Create a new cluster from backup and dont attempt to connect to old known nodes
  • docker swarm join-token: Lists join security token to join another node in swarm as worker or manager
    • –quite: Only display token. By default, it displays complete command to be used along with the token.
    • –rotate: Rotate (change) token for security reasons.
  • docker swarm join: Join already running swarm as a worker or manager
    • –token: Security token to join the swarm
    • –availability: Mark node’s status as active/drain/pause after joining
  • docker swarm leave: Leave swarm. To be run from the node itself
    • -f: Leave forcefully ignoring all warnings.
  • docker swarm unlock: Unlocks swarm by providing key after manager restarts
  • docker swarm unlock-key: Display swarm unlock key
    • -q: Only display token.
    • –rotate: Rotate (change) token for security reasons.
  • docker swarm update: Updates swarm configurations
    • –autolock: true/false. Turns on or off locking if not done while initiating.

Docker swarm node commands for swarm node management

Node is a server participating in Docker swarm. A node can either be a worker or manager in the swarm. The manager node has the ability to manage swarm nodes and services along with serving workloads. Worker nodes can only serve workloads.

Opencart

Docker Compose Cheat Sheet

  • docker node ls : Lists nodes in the swarm
    • -q : Only display node Ids
    • –format : Format output using GO format
    • –filter : Apply filters to output
  • docker node ps : Display tasks running on nodes
    • Above all switches applies here too.
  • docker node promote : Promote node to a manager role
  • docker node demote : Demote node from manager to worker role
  • docker node rm : Remove node from the swarm. Run from the manager node.
    • -f : Force remove
  • docker node inspect : Detailed information about the node
    • –format : Format output using GO format
    • –pretty : Print in a human-readable friendly format
  • docker node update : Update node configs
    • –role : worker/manager. Update node role
    • –availability : active/pause/drain. Set node state.
Docker Commands The Ultimate Cheat Sheet

Docker swarm service commands for swarm service management

Docker service is used to create and spawn workloads to swarm nodes.

Docker Commands The Ultimate Cheat Sheet Download

  • docker service create : Start new service in Docker swarm
    • Switches of docker container run command like -i (interactive), -t (pseud terminal), -d (detached), -p (publish port) etc supported here.
  • docker service ls : List services
    • –filter, –format and -q (quiet) switches which we saw above are supported with this command.
  • docker service ps : Lists tasks of services
    • –filter, –format and -q (quiet) switches which we saw above are supported with this command.
  • docker service logs : Display logs of service or tasks
  • docker service rm : Remove service
    • -f : Force remove
  • docker service update : Update service config
    • Most of the parameters defined in service create command can be updated here.
  • docker service rollback : Revert back changes done in service config.
  • docker service scale : Scale one or more replicated services.
    • servicename=number format
  • docker service inspect : Detailed information about service.