Tidy up apt packages

[psychemedia]

Apt installs can be tidied up and layer size reduced by adding an && apt-get clean && rm -rf /var/lib/apt/lists/* tidy up step.

Unwanted packages can be limited by a --no-install-recommmends switch in an apt-get command.

To impact on layer size, the apt-get clean needs running as part of every apt-get layer, which means that multiple layers need their own apt-get update.

However, just running it once does make for a slightly cleaner filesystem in the final container.

[psychemedia]

The clean may also clobber sources?

[mmh352]

Clobber sources in what way?

[psychemedia]

Delete the path to them. I just checked, you don't, they go to /etc/apt/sources.list.d/ and the clean up cleans /var/lib/apt/lists/*.

The addition of the lists adds time to each apt-get update though. If you have the iterated Dockerfile builder that builds up from several files, and each apt-get step has its own apt-get update and clean step, and each adds its own sources, the source list could get very long and the apt-get update could take forever on the final step.

Most of the time this won't be an issue. Just noting what could happen, though.

[mmh352]

Ok. Well, it is the classic memory vs processing time tradeoff.

[psychemedia]

Three options:

• leave it as is;
• tidy up as a final step (the lists etc will still be baked into lower container layers);
• for each apt-get step, wrap it it apt-get upgrade..apt-clean etc.

The no-recommends is a separate decision which could be set by the user via an optional install-recommends boolean (just need to decide the default) in the config file.

[mmh352]

The base layer already comes with the necessary settings so that apt doesn't cache anything. Removing the /var/lib/apt/lists/* reduces the size by ~10MB on the big demo, so is really not worth it.