hadolint: Dockerfile Linter JavaScript API

[ development, gpl, library, program ] [ Propose Tags ]

A smarter Dockerfile linter that helps you build best practice Docker images.

[Skip to Readme]
Versions [faq] 1.2.5, 1.2.6, 1.3.0, 1.4.0, 1.5.0, 1.6.0, 1.6.1, 1.6.2, 1.6.3, 1.6.4, 1.6.5, 1.6.6, 1.7.0, 1.7.1, 1.7.2, 1.7.3, 1.7.4, 1.7.5, 1.8.0, 1.9.0, 1.10.1, 1.10.2, 1.10.3, 1.10.4, 1.11.0, 1.11.1, 1.11.2, 1.12.0, 1.13.0, 1.14.0, 1.15.0, 1.16.1, 1.16.2, 1.16.3, 1.17.0, 1.17.1, 1.17.2, 1.17.3, 1.17.6, 1.17.7, 1.18.0, 1.18.1, 1.18.2
Dependencies aeson, async, base (>=4.8 && <5), bytestring, containers, directory (>=1.3.0), filepath, gitrev (>=1.3.1), hadolint, HsYAML, language-docker (>=9.1.2 && <10), megaparsec (>=7.0), mtl, optparse-applicative (>=0.14.0), parallel, ShellCheck (>=0.7.1), split (>=0.2), text, void [details]
License GPL-3.0-only
Copyright Lukas Martinelli
Author Lukas Martinelli
Maintainer me@lukasmartinelli.ch
Category Development
Home page https://github.com/hadolint/hadolint
Source repo head: git clone git@github.com:hadolint/hadolint.git
Uploaded by lorenzo at 2020-10-19T13:47:04Z
Distributions Fedora:1.18.0, NixOS:1.18.0
Executables hadolint
Downloads 17413 total (1097 in the last 30 days)
Rating (no votes yet) [estimated by Bayesian average]
Your Rating
  • λ
  • λ
  • λ
Status Hackage Matrix CI
Docs not available [build log]
All reported builds failed as of 2020-10-19 [all 3 reports]


  • Hadolint
    • Hadolint.Config
    • Formatter
      • Hadolint.Formatter.Checkstyle
      • Hadolint.Formatter.Codacy
      • Hadolint.Formatter.Codeclimate
      • Hadolint.Formatter.Format
      • Hadolint.Formatter.Json
      • Hadolint.Formatter.TTY
    • Hadolint.Lint
    • Hadolint.Rules
    • Hadolint.Shell



Use static linking for the hadolint executable


Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info


Maintainer's Corner

For package maintainers and hackage trustees

Readme for hadolint-1.18.2

[back to package description]

[![Linux/OSX Build Status][travis-img]][travis] [![Windows Build status][appveyor-img]][appveyor] [![GPL-3 licensed][license-img]][license] [![GitHub release][release-img]][release] ![Github downloads][downloads-img] <img align="right" alt="pipecat" width="150" src="https://hadolint.github.io/hadolint/img/cat_container.png" />

Haskell Dockerfile Linter

A smarter Dockerfile linter that helps you build [best practice][] Docker images. The linter is parsing the Dockerfile into an AST and performs rules on top of the AST. It is standing on the shoulders of [ShellCheck][] to lint the Bash code inside RUN instructions.

:globe_with_meridians: Check the online version on hadolint.github.io/hadolint Screenshot

How to use

You can run hadolint locally to lint your Dockerfile.

hadolint <Dockerfile>
hadolint --ignore DL3003 --ignore DL3006 <Dockerfile> # exclude specific rules
hadolint --trusted-registry my-company.com:500 <Dockerfile> # Warn when using untrusted FROM images

Docker comes to the rescue to provide an easy way how to run hadolint on most platforms. Just pipe your Dockerfile to docker run:

docker run --rm -i hadolint/hadolint < Dockerfile


You can download prebuilt binaries for OSX, Windows and Linux from the latest [release page][]. However, if it doesn't work for you, please fall back to Docker, brew or source installation.

If you are on OSX you can use brew to install hadolint.

brew install hadolint

On Windows you can use scoop to install hadolint.

scoop install hadolint

As shown before, hadolint is available as a Docker container:

docker pull hadolint/hadolint

If you need a Docker container with shell access, use the Debian or Alpine variants of the Docker image:

docker pull hadolint/hadolint:latest-debian
docker pull hadolint/hadolint:latest-alpine

You can also build hadolint locally. You need [Haskell][] and the [stack][] build tool to build the binary.

git clone https://github.com/hadolint/hadolint
cd hadolint
stack install


hadolint supports specifying the ignored rules using a configuration file. The configuration file should be in yaml format. This is one valid configuration file as an example:

  - DL3000
  - SC1010

Additionally, hadolint can warn you when images from untrusted repositories are being used in Dockerfiles, you can append the trustedRegistries keys to the configuration file as shown below:

  - DL3000
  - SC1010

  - docker.io
  - my-company.com:5000

Configuration files can be used globally or per project. By default, hadolint will look for a configuration file in the current directory with the name .hadolint.yaml

The global configuration file should be placed in the folder specified by XDG_CONFIG_HOME, with the name hadolint.yaml. In summary, the following locations are valid for the configuration file, in order or preference:

  • $PWD/.hadolint.yaml
  • $XDG_CONFIG_HOME/hadolint.yaml
  • ~/.config/hadolint.yaml

In windows, the %LOCALAPPDATA% environment variable is used instead of XDG_CONFIG_HOME

Additionally, you can pass a custom configuration file in the command line with the --config option

hadolint --config /path/to/config.yaml Dockerfile

To pass a custom configuration file (using relative or absolute path) to a container, use the following command:

docker run --rm -i -v ./your/path/to/hadolint.yaml:/root/.config/hadolint.yaml hadolint/hadolint < Dockerfile

Inline ignores

It is also possible to ignore rules by using a special comment directly above the Dockerfile instruction you want to make an exception for. Ignore rule comments look like # hadolint ignore=DL3001,SC1081. For example:

# hadolint ignore=DL3006
FROM ubuntu

# hadolint ignore=DL3003,SC1035
RUN cd /tmp && echo "hello!"

Inline ignores will only work if place directly above the instruction.


To get most of hadolint it is useful to integrate it as a check to your CI or to your editor to lint your Dockerfile as you write it. See our [Integration][] docs.

  • [Code Review Platform Integrations][]
  • [Continuous Integrations][]
  • [Editor Integrations][]


An incomplete list of implemented rules. Click on the error code to get more detailed information.

  • Rules with the prefix DL originate from hadolint. Take a look at Rules.hs to find the implementation of the rules.

  • Rules with the SC prefix originate from ShellCheck (Only the most common rules are listed, there are dozens more)

Please [create an issue][] if you have an idea for a good rule.

| Rule | Description | |:-------------------------------------------------------------|:----------------------------------------------------------------------------------------------------------------------------------------------------| | DL3000 | Use absolute WORKDIR. | | DL3001 | For some bash commands it makes no sense running them in a Docker container like ssh, vim, shutdown, service, ps, free, top, kill, mount, ifconfig. | | DL3002 | Last user should not be root. | | DL3003 | Use WORKDIR to switch to a directory. | | DL3004 | Do not use sudo as it leads to unpredictable behavior. Use a tool like gosu to enforce root. | | DL3005 | Do not use apt-get upgrade or dist-upgrade. | | DL3006 | Always tag the version of an image explicitly. | | DL3007 | Using latest is prone to errors if the image will ever update. Pin the version explicitly to a release tag. | | DL3008 | Pin versions in apt-get install. | | DL3009 | Delete the apt-get lists after installing something. | | DL3010 | Use ADD for extracting archives into an image. | | DL3011 | Valid UNIX ports range from 0 to 65535. | | DL3012 | Provide an email address or URL as maintainer. | | DL3013 | Pin versions in pip. | | DL3014 | Use the -y switch. | | DL3015 | Avoid additional packages by specifying --no-install-recommends. | | DL3016 | Pin versions in npm. | | DL3017 | Do not use apk upgrade. | | DL3018 | Pin versions in apk add. Instead of apk add <package> use apk add <package>=<version>. | | DL3019 | Use the --no-cache switch to avoid the need to use --update and remove /var/cache/apk/* when done installing packages. | | DL3020 | Use COPY instead of ADD for files and folders. | | DL3021 | COPY with more than 2 arguments requires the last argument to end with / | | DL3022 | COPY --from should reference a previously defined FROM alias | | DL3023 | COPY --from cannot reference its own FROM alias | | DL3024 | FROM aliases (stage names) must be unique | | DL3025 | Use arguments JSON notation for CMD and ENTRYPOINT arguments | | DL3026 | Use only an allowed registry in the FROM image | | DL3027 | Do not use apt as it is meant to be a end-user tool, use apt-get or apt-cache instead | | DL3028 | Pin versions in gem install. Instead of gem install <gem> use gem install <gem>:<version> | | DL3029 | Do not use --platform flag with FROM. | | DL3030 | Use the -y switch to avoid manual input yum install -y <package> | | DL3031 | Do not use yum update | | DL3032 | yum clean all missing after yum command. | | DL3033 | Specify version with yum install -y <package>-<version> | | DL4000 | MAINTAINER is deprecated. | | DL4001 | Either use Wget or Curl but not both. | | DL4003 | Multiple CMD instructions found. | | DL4004 | Multiple ENTRYPOINT instructions found. | | DL4005 | Use SHELL to change the default shell. | | DL4006 | Set the SHELL option -o pipefail before RUN with a pipe in it | | SC1000 | $ is not used specially and should therefore be escaped. | | SC1001 | This \c will be a regular 'c' in this context. | | SC1007 | Remove space after = if trying to assign a value (or for empty string, use var='' ...). | | SC1010 | Use semicolon or linefeed before done (or quote to make it literal). | | SC1018 | This is a unicode non-breaking space. Delete it and retype as space. | | SC1035 | You need a space here | | SC1045 | It's not foo &; bar, just foo & bar. | | SC1065 | Trying to declare parameters? Don't. Use () and refer to params as $1, $2 etc. | | SC1066 | Don't use $ on the left side of assignments. | | SC1068 | Don't put spaces around the = in assignments. | | SC1077 | For command expansion, the tick should slant left (` vs ยด). | | SC1078 | Did you forget to close this double-quoted string? | | SC1079 | This is actually an end quote, but due to next char, it looks suspect. | | SC1081 | Scripts are case sensitive. Use if, not If. | | SC1083 | This {/} is literal. Check expression (missing ;/\n?) or quote it. | | SC1086 | Don't use $ on the iterator name in for loops. | | SC1087 | Braces are required when expanding arrays, as in ${array[idx]}. | | SC1095 | You need a space or linefeed between the function name and body. | | SC1097 | Unexpected ==. For assignment, use =. For comparison, use [ .. ] or [[ .. ]]. | | SC1098 | Quote/escape special characters when using eval, e.g. eval "a=(b)". | | SC1099 | You need a space before the #. | | SC2002 | Useless cat. Consider <code>cmd < file | ..</code> or <code>cmd file | ..</code> instead. | | SC2015 | Note that <code>A && B || C</code> is not if-then-else. C may run when A is true. | | SC2026 | This word is outside of quotes. Did you intend to 'nest '"'single quotes'"' instead'? | | SC2028 | echo won't expand escape sequences. Consider printf. | | SC2035 | Use ./*glob* or -- *glob* so names with dashes won't become options. | | SC2039 | In POSIX sh, something is undefined. | | SC2046 | Quote this to prevent word splitting | | SC2086 | Double quote to prevent globbing and word splitting. | | SC2140 | Word is in the form "A"B"C" (B indicated). Did you mean "ABC" or "A\"B\"C"? | | SC2154 | var is referenced but not assigned. | | SC2155 | Declare and assign separately to avoid masking return values. | | SC2164 | Use <code>cd ... || exit</code> in case cd fails. |


If you are an experienced Haskeller we would be really thankful if you would tear our code apart in a review.


  1. Clone repository

    git clone --recursive git@github.com:hadolint/hadolint.git
  2. Install the dependencies

    stack install


The easiest way to try out the parser is using the REPL.

# start the repl
stack repl
# overload strings to be able to use Text
:set -XOverloadedStrings
# import parser library
import Language.Docker
# parse instruction and look at AST representation
parseText "FROM debian:jessie"


Run unit tests.

stack test

Run integration tests.



Dockerfile syntax is fully described in the [Dockerfile reference][]. Just take a look at [Syntax.hs][] in the language-docker project to see the AST definition.


<!-- References --> [travis-img]: https://travis-ci.org/hadolint/hadolint.svg?branch=master [travis]: https://travis-ci.org/hadolint/hadolint [appveyor-img]: https://ci.appveyor.com/api/projects/status//github/hadolint/hadolint?svg=true&branch=master [appveyor]: https://ci.appveyor.com/project/hadolint/hadolint/branch/master [license-img]: https://img.shields.io/badge/license-GPL--3-blue.svg [license]: https://tldrlegal.com/l/gpl-3.0 [release-img]: https://img.shields.io/github/release/hadolint/hadolint.svg [release]: https://github.com/hadolint/hadolint/releases/latest [downloads-img]: https://img.shields.io/github/downloads/hadolint/hadolint/total.svg [best practice]: https://docs.docker.com/engine/userguide/eng-image/dockerfile_best-practices [shellcheck]: https://github.com/koalaman/shellcheck [release page]: https://github.com/hadolint/hadolint/releases/latest [haskell]: https://www.haskell.org/platform/ [stack]: http://docs.haskellstack.org/en/stable/install_and_upgrade.html [integration]: docs/INTEGRATION.md [code review platform integrations]: docs/INTEGRATION.md#code-review [continuous integrations]: docs/INTEGRATION.md#continuous-integration [editor integrations]: docs/INTEGRATION.md#editors [create an issue]: https://github.com/hadolint/hadolint/issues/new [dockerfile reference]: http://docs.docker.com/engine/reference/builder/ [syntax.hs]: https://www.stackage.org/haddock/nightly-2018-01-07/language-docker-2.0.1/Language-Docker-Syntax.html