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
How to use
You can run
hadolint locally to lint your Dockerfile.
hadolint <Dockerfile> hadolint --ignore DL3003 --ignore DL3006 <Dockerfile> # exclude specific rules
Docker comes to the rescue to provide an easy way how to run
hadolint on most platforms.
Just pipe your
docker run --rm -i lukasmartinelli/hadolint < Dockerfile
You can download prebuilt binaries for OSX, Windows and Linux from the latest release page. However they may not run on your system configuration since I am not able to provide completely statically linked binaries. Fall back to
brew, source installation or Docker if it doesn't work for you.
If you are on OSX you can use brew to install hadolint.
brew install hadolint
git clone https://github.com/lukasmartinelli/hadolint cd hadolint stack build
Incomplete list of implemented rules. Click on the error code to get more detailed information.
- Rules with the prefix
DLoriginate from hadolint. Take a look into
Rules.hsto find the implementation of the rules.
- Rules with the
SCprefix 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.
|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||Do not switch to root USER.|
|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.|
|DL3007||Using latest is prone to errors if the image will ever update. Pin the version explicitly to a release tag.|
|DL3006||Always tag the version of an image explicitly.|
|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.|
|DL3015||Avoid additional packages by specifying --no-install-recommends.|
|DL4000||Specify a maintainer of the Dockerfile.|
|DL4001||Either use Wget or Curl but not both.|
|SC1007||Remove space after
|SC1010||Use semicolon or linefeed before
|SC1018||This is a unicode non-breaking space. Delete it and retype as space.|
|SC1035||You need a space here|
|SC1065||Trying to declare parameters? Don't. Use
|SC1066||Don't use $ on the left side of assignments.|
|SC1068||Don't put spaces around the
|SC1077||For command expansion, the tick should slant left (` vs ´).|
|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
|SC1087||Braces are required when expanding arrays, as in
|SC1095||You need a space or linefeed between the function name and body.|
|SC1098||Quote/escape special characters when using
|SC1099||You need a space before the
|SC2002||Useless cat. Consider `cmd < file|
|SC2015||Note that `A && B|
|SC2026||This word is outside of quotes. Did you intend to 'nest '"'single quotes'"' instead'?|
|SC2046||Quote this to prevent word splitting|
|SC2086||Double quote to prevent globbing and word splitting.|
|SC2140||Word is on the form
|SC2154||var is referenced but not assigned.|
|SC2164||Use `cd ...|
This is my first Haskell program. If you are an experienced Haskeller I would be really thankful if you would tear my code apart in a review.
- Clone repository
git clone --recursive firstname.lastname@example.org:lukasmartinelli/hadolint.git
- Install the dependencies
The easiest way to try out the parser is using the REPL.
# start the repl stack repl # parse instruction and look at AST representation parseString "FROM debian:jessie"
Run unit tests.
Run integration tests.
The Dockerfile is parsed using Parsec and is using the lexer
Lexer.hs and parser
Dockerfile syntax is fully described in the Dockerfile reference. Just take a look at
Syntax.hs to see the AST definition.