Authentication

By default, WUD's web interface is accessible to everyone. To prevent network-wide access to view or trigger actions on your containers, define users and passwords. WUD will then require authentication. First, create a password hash compatible with the Apache web server's htpasswd tool. If you don't have the tool installed, just use OpenSSL:

$ openssl passwd -apr1 my_secret_password

The output resembles $apr1$xKTGamqS$x5d43GZTZfPDP4Sb3KK0p0, consisting of three parts separated by a dollar sign: the hash algorithm (apr1), the salt (a random string), and the hash value of the password and salt combined in Base64.

Next, add the username and the corresponding password hash as environment variables to the WUD container, while ensuring to duplicate each dollar sign:

environment:
      - WUD_AUTH_BASIC_KOAN_USER=koan
      - WUD_AUTH_BASIC_KOAN_HASH=$$apr1$$xKTGamqS$$x5d43GZTZfPDP4Sb3KK0p0

To define multiple users, just add more environment variables following the same process, adjusting the username accordingly.

Note that WUD operates over an unencrypted HTTP connection by default. For increased security, using HTTPS is wise. You can find instructions on enabling HTTPS and configuring a certificate and private key in WUD's documentation. Alternatively, run WUD behind a reverse proxy that handles HTTPS connections.

Alternatives to What's up Docker?

WUD is not the only open source solution for monitoring and updating container images. A popular alternative is watchtower [12], which focuses on automatically updating containers when a new image version is available, although it also offers update monitoring. However, it lacks a web interface. Another alternative, Diun [13], stands for Docker Image Update Notifier. It focuses on update monitoring, but also without a web interface. The choice of tool depends on your priorities, but WUD is the most versatile solution among these three.

Conclusion

WUD offers a flexible way to monitor your containers for updates of their images. This article only covers the basics, but extensive customization options are available. For example, you can override many of the program's general settings for specific containers, and you can assign different triggers to different containers.

The Author

Koen Vervloesem has been writing about Linux and open source, computer security, privacy, programming, artificial intelligence, and the Internet of Things for more than 25 years. He holds Master's degrees in Computer Science Engineering and Philosophy and is teaching Linux, Python, and IoT classes. You can find more on his website at http://koen.vervloesem.eu.