David Wesst

Docker Build Hangs When Adding Key with apt-key in WSL2

2023-01-11T12:00:00-06:00
  • blog
  • docker
  • wsl2
  • apt-key
  • debian
  • linux
  • devcontainer
    •      A light blue cartoon style whale, meant to resemble the Docker logo, with a yellow-orange beak, like the Linux penguin, holding a key in it's mouth. Drawn with very small squares.

    Problem

    When trying to add a key using apt-key on a Debian 11 docker image, the step seems to run infinitely.

    The screenshot below highlights this problem when adding a key that is necessary to validate the mono-complete package.

    A terminal window showing the steps of a docker build command along with their run times. The command that is currently being run is an apt-key command that is still running after 8078.8 seconds

    Details

    I setup a DevContainer to build Inky, a interactive fiction editor I like for game projects, without having to install all the build dependencies on my local machine. The Docker container build worked on my Linux machine, but would hang on my Windows 11 box, using Docker Desktop with WSL2. More specifically, it would run forever on the apt-key command, as specified by the mono install instructions.

    If you need an example, take a look at my Inky repository fork at that specific point.

    Solution

    The issue was that the command specifically references port 80 in the URL to the keyserver. In the end, I changed:

    sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF

    to

    sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF

    You can see the specifics in the next commit in my example repository in the following commit here.

    Reference

    I was put on the right track with a Stack Overflow post trying to solve a similar issue with apt-key. Scrolling through the answers, I found this one: LINK

    apt-key Deprecation Notice

    If you look at the Debian documentation for apt-key or try running the command yourself, you might notice the deprecation warning. Underneath the hood, it runs the appropriate command in Debian 11, but will be gone after Debian 11 and Ubuntu 22.04.

    Just something to note for those looking over this solution in the future.

    Conclusion / TL;DR;

    I needed to remove the port number from the keyserver URL used in my apt-key command.

    Thanks for playing.

    ~ DW