python + docker：docker卷挂载错误，数据静默丢失

Question

I'm running into an issue without volume mounting, combined with the creation of directories in python.

Essentially inside my container, I'm writing to some path /opt/… , and I may have to make the path (which I'm using os.makedirs for)

If I mount a host file path like -v /opt:/opt , with bad "permissions" where the docker container does not seem to be able to write to, the creation of the path inside the container DOES NOT FAIL. The makedirs(P) works, because inside the container, it can make the dir just fine, because it has sudo permissions. However, nothing gets written, silently, on the host at /opt/… . The data just isn't there, but no exception is ever raised.

If I mount a path with proper/open permissions, like -v /tmp:/opt , then the data shows up on the host machine at /tmp/… as expected.

So, how do I not silently fail if there are no write permissions on the host on the left side of the -v argument?\\

EDIT: my question is "how do I detect this bad deployment scenario, crash, and fail fast inside the container, if the person who deploys the container, does it wrong"? Just silently not writing data isn't acceptable.

Answer 1

The bad mount is root on the host right, and the good mount is the user in the Docker group on the host? Can you check the user/group of the mounted /opt ? It should be different than that of /tmp .

Answer 2

You could expect a special file to exist in /opt and fail if it's not present

if not os.path.exists(PATH):
    raise Exception("could not find PATH: file missing or failed to mount /opt")