Starting and stoping containers, and the exec-pre-backup and exec-post-backup commands also do not work anymore.

Oh shoot, I thought I tested that... did you manage to sort it out for yourself @jan-brinkmann?

Hello @jan-brinkmann , sorry by my late reply.

It could be related to #53 because I move docker binary from /usr/bin to /usr/local/bin. This new place is not a feature, only following donator's schema. Therefore, if PATH is different between images or archs, this change unraveled it.

Could you please print the PATH (echo $PATH) and exec which docker (1) inside container and (2) inside POST_BACKUP_COMMAND?

On the other hand, I'm not able to reproduce the issue. which docker:

• amd64 OK
• arm/v7 KO+OK

arm failed to build due to docker:latest only supports amd64 and arm64/v8 right now. I switched to docker:stable to make it work. Sadly, inner and outer versions of docker will not be the same anymore with this change.
See: docker-library/docker#357

Finally reproduced....
Testing it through docker-compose exec backup ./backup.sh (as recommended at Readme) will give following PATH: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

But cron execution chunks the PATH to /usr/bin:/bin by default. Here is the problem.

Therefore there are 2 options to fixup:
a) Move back docker to 'minimal PATH'

-COPY --from=docker:latest /usr/local/bin/docker /usr/local/bin/
+COPY --from=docker:latest /usr/local/bin/docker /usr/bin/

b) make PATH consistent inside and outside cron

-echo "$BACKUP_CRON_EXPRESSION root /root/backup.sh > /proc/1/fd/1 2>&1" > /etc/cron.d/docker-volume-backup
+cat<<EOF>/etc/cron.d/docker-volume-backup
+PATH=$PATH
+$BACKUP_CRON_EXPRESSION root /root/backup.sh > /proc/1/fd/1 2>&1
+EOF

I prefer (b), so a PR is incoming

Works well for my use case.

Thank you, @varhub!

I do get the error again in the current version. It seems like the changes considering the PATH to the entrypoint.sh in the Pull request back then are no longer in the file. Is this by design?