All of your diagnostics that you’ve posted are from the PoV of your host, not your container. You need to diagnose the status within the built container, not your host.
cd ~/lucee
docker build -t testimage .
docker run -d --name testimage testimage
Now lucee is running with your built image.
docker exec -it testimage bash
ls -ld /
ls -ld /var
ls -ld /var/www
ls -l /var/www
Verify all that works
Determine the processes running.
apt-get update
apt-get install procps
ps awwux
Following these steps it looks to me like most things are good based on what you’ve provided, you SHOULD be able to write to that file… so here’s the next question… Did you try to append or write to /var/www/textfile.json?
I don’t mean expandpath, I mean the ACTUAL ABSOLUTE path.
Or did you try to cfoutput the expandpath results and verify you’re actually getting the file path you think…
When I copy your example code into application.cfc and run it, it works. And by it works, I mean:
docker exec -it testimage cat /var/www/textfile.json
Returns the proper result.
If you’re expecting ~userme/lucee/www to change on the host, you don’t want to create a build, you want a volume mount.
Cleanups
docker stop testimage
docker rm testimage
Interactive dev environment
docker run -d --rm -p 8888:8888 --name testimage -v /home/userme/lucee/www:/var/www lucee/lucee4
docker logs testimage
Or run without the name, swap -d for -it, and just ctrl-c when done. No build necessary.
So based on what you’re reporting, my guess is it IS writing to the file, in /var/www, in the container, which is a COPY of your files. But that’s not where you’re looking. 