Docker cannot write files to host with correct permissions. Why UID is 0 when running builds?

[dgullo]

Correction: the UID is not the problem. For some reason the mounting of the docker volumes is still not working correctly and suffering some permission errors on bitbucket.

In order to cache the composer folder i was mounting ./.composer to /home/composer/.composer .

- ./.composer:/home/composer/.composer


This was causing permission errors, so changed it so that the current folder is also mounted at /home/composer  but this is also not working.

- ./:/home/composer/

I have also added step

- "ls -la .composer/cache/repo"

in the pipeline file to debug what is happening and this is failing. 
+ ls -la .composer/cache/repoCreating build_composer_1 ... donels: .composer/cache/repo: No such file or directory

And also it is clear from composer install that the container is not able to write to the cache:

Cannot create cache directory /home/composer/.composer/cache/repo/https---repo.packagist.org/, or directory is not writable. Proceeding without cacheCannot create cache directory /home/composer/.composer/cache/files/, or directory is not writable. Proceeding without cacheLoading composer repositories with package informationInstalling dependencies (including require-dev) from lock file

How am i supposed to leverage the composer caching as shown on this document if my container cannot write the files to the host?

Original post below

--------------------------------

Problem, when running a build on bitbucket the runner has not UID and thus volumes cannot be mounted correctly, See step output :

 + export UID && echo " UID: $UID "
UID: 0

Mounting a container volume with the right UID is necessary so that new files can be mounted and written back to the volume.

In my case this is stopping composer (php) when creating files back to the volume and so the vendor folder needs to be recreated from connecting back to packagist every time. I could also try to cache manually the vendor folder but Bitbucket is a very different and not standard environment so I cannot really play too much with it also because of the 50 minutes build time limit on a monthly basis.

In a similar article but back from time it looks like docker was able to write files back as the container user which is usually root but without a UID mapping this cannot be achieved with the correct permissions.

https://community.atlassian.com/t5/Bamboo-questions/Bamboo-docker-Could-not-remove-working-directory-for-plan/qaq-p/66819

Can someone suggest how to achieve a correct UID mapping on bitbucket?

here is also an extract of the bitbucket pipelines yml file

options:
  docker: true

pipelines:
  default:
    - step:
        caches:
          - docker
          - composer
        script:
          - "export UID && echo \" UID: $UID \""
          - "export UID && make tests_ci"

definitions:
  caches:
    composer: ./.composer 

[Radek Antoniuk]

Take a look at the questions below that will help you debug this:

• https://community.atlassian.com/t5/Bitbucket-questions/Bitbucket-pipelines-does-Docker-volume-mounting-work-yet/qaq-p/703455
• https://confluence.atlassian.com/bitbucket/debug-your-pipelines-locally-with-docker-838273569.html

Having UID=0 is quite common when using docker, you can read about it here.

[dgullo]

It is quite common indeed, all the issues i see about permissions on bitbucket pipelines are quite uncommon though as you can see maybe bitbucket clone dir subdirectories might not be mountable as shown here. I will try to refactor and see if it works 
https://community.atlassian.com/t5/Bitbucket-questions/Bitbucket-pipelines-how-can-I-map-a-volume-to-docker-to-expose/qaq-p/686951#M22253

[dgullo]

BTW i have updated my post with some extra information.