Allow caching of additional gems #27
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Somehow the caching as described in the README.md file didn't work for
me. It might be, because I need additional gems for my Jekyll builds,
but I don't exactly know. The changes in this commit seem to fix the
problem.
- The changes in the Dockerfile create a new directory for gems that
someone might want to install additionally (optionally) to the ones
that are already installed in the container image.
- The changes in the entrypoint file do two things:
- The export `GEM_PATH`. This is done to keep `/usr/gem` in the list
of directories that ruby looks for gems. So far ruby only looks in
`/usr/gem` for gems, because `GEM_HOME` points to that directory.
But because I want to overwrite `GEM_HOME` with `/opt/gem` the
`/usr/gem` directory has to be explicitly saved in `GEM_PATH`.
- Overwrite the `GEM_HOME` environment variable. This way ruby looks
for gems in `/opt/gem`.
- The changes in README.md instruct the user of the image to mount a
lokal directory on the host into the `/opt/gem` directory in the
container. This way, additionally installed gems are stored
persistently on the host and can be used in subsequent containers that
are started from the container image.
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Background and Suggested Fix
Somehow the caching as described in the README.md file didn't work for me. It might be, because I need additional gems for my Jekyll builds, but I don't exactly know. The changes in this commit seem to fix the problem.
GEM_PATH. This is done to keep/usr/gemin the list of directories that ruby looks for gems. So far ruby only looks in/usr/gemfor gems, becauseGEM_HOMEpoints to that directory. But because I want to overwriteGEM_HOMEwith/opt/gemthe/usr/gemdirectory has to be explicitly saved inGEM_PATH.GEM_HOMEenvironment variable. This way ruby looks for gems in/opt/gem./opt/gemdirectory in the container. This way, additionally installed gems are stored persistently on the host and can be used in subsequent containers that are started from the container image.Missing Tests Build
Unfortunately, I couldn't build the new image locally on my machine. It must have to do with the opts.yml files. But I have had this problem a long time (already with the images built by envygeeks). To fix this, I used the suggested changes in the pull request to build my one image on top of the images from envygeeks. And that worked.