bvwells / hadolint-example

Hadolint Dockerfile Linting Example

Hadolint Example

This repo shows an example of linting a Docker file with Hadolint.

The repo contains two Dockerfiles, the original Dockerfile which Hadolint identifies issues with. Run the command:

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

This command produces the output:

-:6 DL3018 warning: Pin versions in apk add. Instead of `apk add <package>` use `apk add <package>=<version>`
-:6 DL3019 info: Use the `--no-cache` switch to avoid the need to use `--update` and remove `/var/cache/apk/*` when done installing packages
-:11 DL3047 info: Avoid use of wget without progress bar. Use `wget --progress=dot:giga <url>`.Or consider using `-q` or `-nv` (shorthands for `--quiet` or `--no-verbose`).

See rules for more information on how to fix these issues.

Note: when pinning alpine package versions it is useful to refer to the official alpine package management site here. Also, it is possible to idenitfy the versions of packages by building the Docker image without pinning the versions and then run apk info *package* within the running container to see the version which was installed without pinning.

To build the Dockerfiles run

cd original && docker build -t bvwells/hadolint-example/original .

cd updated && docker build -t bvwells/hadolint-example/updated .