Online tools

Dockerfile Linter – Haskell

by

Updated: 18 August 2023

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

Use online at https://hadolint.github.io/hadolint

Run in a Docker container

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

SSL

by

Updated: 11 February 2026

Create self-signed certs

Accept default answers to questions except Common Name, which should be your domain name.

sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout foo.key -out foo.crt

Use the files generated in an Apache virtual host

<VirtualHost *:443>
    ...
    SSLCertificateFile /etc/ssl/certs/foo.crt
    SSLCertificateKeyFile /etc/ssl/private/foo.key
</VirtualHost>

See Digital Ocean, how to create self-signed certs
See Self-signed wildcard cert check project on GitHub

Diagnose problems with certificates

Mozilla SSL configuration generator

https://ssl-config.mozilla.org/