SOLVED Please update Docker on the Cloudron buildserver
cloudron buildthen instructions from more recent Docker version like multi-stage builds or simply copying data from another existing Docker image fail, e.g.:
Step 9/12 : COPY --from=mprasil/bitwarden:1.7.0 /web-vault /app/code/web-vault Unknown flag: from Build failed Build failed ERROR App could not be built due to errors above [ /usr/lib/node_modules/cloudron/src/helper.js:68:29 ]
Multistage builds or the possibility to copy artifacts from existing images (instead of compiling everything from scratch on top of the cloudron base image) reduce the size for additional layers and could greatly ease app development.
I believe this is a known issue. They might be working on it already.
@murgero yes, I brought this up already in the bitwarden topic, but since this could be helpful in other scenarios I wanted to post it on its own.
With the above dockerfile cloudron build now succeeds.
I have a longer train ride on friday, maybe I can make something happen with bitwarden during it.