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hadolint

hadolint documentation

hadolint - GitHub

Configuration in Mega-Linter

Variable Description Default value
DOCKERFILE_HADOLINT_ARGUMENTS User custom arguments to add in linter CLI call
Ex: -s --foo "bar"
DOCKERFILE_HADOLINT_FILTER_REGEX_INCLUDE Custom regex including filter
Ex: (src\|lib)		 Include every file
DOCKERFILE_HADOLINT_FILTER_REGEX_EXCLUDE Custom regex excluding filter
Ex: (test\|examples)		 Exclude no file
DOCKERFILE_HADOLINT_CLI_LINT_MODE Override default CLI lint mode
- file: Calls the linter for each file
- list_of_files: Call the linter with the list of files as argument
- project: Call the linter from the root of the project		 {linter.cli_lint_mode}
DOCKERFILE_HADOLINT_FILE_EXTENSIONS Allowed file extensions. "*" matches any extension, "" matches empty extension. Empty list excludes all files
Ex: [".py", ""]		 Exclude every file
DOCKERFILE_HADOLINT_FILE_NAMES_REGEX File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files
Ex: ["Dockerfile(-.+)?", "Jenkinsfile"]		 ["Dockerfile"]
DOCKERFILE_HADOLINT_PRE_COMMANDS List of bash commands to run before the linter None
DOCKERFILE_HADOLINT_POST_COMMANDS List of bash commands to run after the linter None
DOCKERFILE_HADOLINT_CONFIG_FILE hadolint configuration file name
Use LINTER_DEFAULT to let the linter find it		 .hadolint.yml
DOCKERFILE_HADOLINT_RULES_PATH Path where to find linter configuration file Workspace folder, then Mega-Linter default rules
DOCKERFILE_HADOLINT_DISABLE_ERRORS Run linter but consider errors as warnings false
DOCKERFILE_HADOLINT_DISABLE_ERRORS_IF_LESS_THAN Maximum number of errors allowed 0

IDE Integration

Use hadolint in your favorite IDE to catch errors before Mega-Linter !

IDE Extension Name Install
Atom linter-hadolint Visit Web Site
Visual Studio Code hadolint Install in VsCode

Mega-Linter Flavours

This linter is available in the following flavours

Flavor Description Embedded linters Info
all Default Mega-Linter Flavor 93 Docker Image Size (tag) Docker Pulls
ci_light Optimized for CI items (Dockerfile, Jenkinsfile, JSON/YAML schemas,XML 13 Docker Image Size (tag) Docker Pulls
dart Optimized for DART based projects 40 Docker Image Size (tag) Docker Pulls
documentation Mega-Linter for documentation projects 39 Docker Image Size (tag) Docker Pulls
dotnet Optimized for C, C++, C# or VB based projects 46 Docker Image Size (tag) Docker Pulls
go Optimized for GO based projects 41 Docker Image Size (tag) Docker Pulls
java Optimized for JAVA based projects 41 Docker Image Size (tag) Docker Pulls
javascript Optimized for JAVASCRIPT or TYPESCRIPT based projects 48 Docker Image Size (tag) Docker Pulls
php Optimized for PHP based projects 43 Docker Image Size (tag) Docker Pulls
python Optimized for PYTHON based projects 48 Docker Image Size (tag) Docker Pulls
ruby Optimized for RUBY based projects 40 Docker Image Size (tag) Docker Pulls
rust Optimized for RUST based projects 40 Docker Image Size (tag) Docker Pulls
salesforce Optimized for Salesforce based projects 42 Docker Image Size (tag) Docker Pulls
scala Optimized for SCALA based projects 40 Docker Image Size (tag) Docker Pulls
swift Optimized for SWIFT based projects 40 Docker Image Size (tag) Docker Pulls
terraform Optimized for TERRAFORM based projects 44 Docker Image Size (tag) Docker Pulls

Behind the scenes

How are identified applicable files

  • File names (regex): Dockerfile

How the linting is performed

  • hadolint is called one time by identified file

Example calls

hadolint Dockerfile

hadolint --config .hadolint.yml Dockerfile

Help content

hadolint - Dockerfile Linter written in Haskell

Usage: hadolint [-v|--version] [--no-fail] [--no-color] [-c|--config FILENAME]
                [-V|--verbose] [-f|--format ARG] [DOCKERFILE...]
                [--error RULECODE] [--warning RULECODE] [--info RULECODE]
                [--style RULECODE] [--ignore RULECODE]
                [--trusted-registry REGISTRY (e.g. docker.io)]
                [--require-label LABELSCHEMA (e.g. maintainer:text)]
                [--strict-labels] [-t|--failure-threshold THRESHOLD]
                [--file-path-in-report FILEPATHINREPORT]
  Lint Dockerfile for errors and best practices

Available options:
  -h,--help                Show this help text
  -v,--version             Show version
  --no-fail                Don't exit with a failure status code when any rule
                           is violated
  --no-color               Don't colorize output
  -c,--config FILENAME     Path to the configuration file
  -V,--verbose             Enables verbose logging of hadolint's output to
                           stderr
  -f,--format ARG          The output format for the results [tty | json |
                           checkstyle | codeclimate | gitlab_codeclimate |
                           codacy | sonarqube] (default: tty)
  --error RULECODE         Make the rule `RULECODE` have the level `error`
  --warning RULECODE       Make the rule `RULECODE` have the level `warning`
  --info RULECODE          Make the rule `RULECODE` have the level `info`
  --style RULECODE         Make the rule `RULECODE` have the level `style`
  --ignore RULECODE        A rule to ignore. If present, the ignore list in the
                           config file is ignored
  --trusted-registry REGISTRY (e.g. docker.io)
                           A docker registry to allow to appear in FROM
                           instructions
  --require-label LABELSCHEMA (e.g. maintainer:text)
                           The option --require-label=label:format makes
                           Hadolint check that the label `label` conforms to
                           format requirement `format`
  --strict-labels          Do not permit labels other than specified in
                           `label-schema`
  -t,--failure-threshold THRESHOLD
                           Exit with failure code only when rules with a
                           severity equal to or above THRESHOLD are violated.
                           Accepted values: [error | warning | info | style |
                           ignore | none] (default: info)
  --file-path-in-report FILEPATHINREPORT
                           The file path referenced in the generated report.
                           This only applies for the 'checkstyle' format and is
                           useful when running Hadolint with Docker to set the
                           correct file path.

Installation on mega-linter Docker image

  • Dockerfile commands :
FROM hadolint/hadolint:latest-alpine as hadolint
COPY --from=hadolint /bin/hadolint /usr/bin/hadolint

Example success log

Results of hadolint linter (version 1.19.0)
See documentation on https://nvuillam.github.io/mega-linter/descriptors/dockerfile_hadolint/
-----------------------------------------------

[SUCCESS] .automation/test/docker/good/Dockerfile


[SUCCESS] .automation/test/docker/good/Dockerfile.dev

Example error log

Results of hadolint linter (version 1.19.0)
See documentation on https://nvuillam.github.io/mega-linter/descriptors/dockerfile_hadolint/
-----------------------------------------------

[ERROR] .automation/test/docker/bad/Dockerfile
    .automation/test/docker/bad/Dockerfile:1 DL3007 Using latest is prone to errors if the image will ever update. Pin the version explicitly to a release tag
    .automation/test/docker/bad/Dockerfile:8 DL3021 COPY with more than 2 arguments requires the last argument to end with /
    .automation/test/docker/bad/Dockerfile:9 DL3004 Do not use sudo as it leads to unpredictable behavior. Use a tool like gosu to enforce root
    .automation/test/docker/bad/Dockerfile:11 DL3020 Use COPY instead of ADD for files and folders
    .automation/test/docker/bad/Dockerfile:14 DL3025 Use arguments JSON notation for CMD and ENTRYPOINT arguments