Mounted docker volumes corrupting files

Question

I think this is machine related, but I'm not sure. I'm using the most current docker toolbox with docker 1.10.3 on OSX I have a project using a Dockerfile, which copies code into the container like this:

[...]
COPY . /code
VOLUME /code
WORKDIR /code
[...]

For faster local development (test execution), we mount the current directory in the compose file

[...]
volumes:
      - .:/code
[...]

and execute

docker-compose -f docker-compose.yml -f docker-compose.testing.yml run web py.test

Now, it looks like I have two different folders/files: when running the container and looking inside a file with vi, everything looks like on the host. Changing files and executing our tests (pytest, specifically) lets the python interpreter read garbage so it can't execute the tests.

Example

the end of a file looks like this (which got copied in the Dockerfile into the container):

post_save.connect(backup_something, sender=SomeSender, dispatch_uid='backup_something') foobar
this obviously raises an error when executing, so I change it to

post_save.connect(backup_something, sender=SomeSender, dispatch_uid='backup_something')

the file looks fine now, both from the host and inside the container. Executing pytest, it still reads the content of the copied code, breaking the tests locally for me.

If I change even more, it's neither the copied nor the mounted file, so stuff breaks at random positions:

File "/code/some_code.py", line 69
    dispatch_uid='backup_
                        ^

SyntaxError: EOL while scanning string literal (tail shows correct syntax etc, there is definitely nothing broken with the code)

Is there something wrong with our setup or is it just my machine being broken somehow? I tried restarting and recreating the docker machine but this doesn't help.

Answer 1

I would try to mount in read only mode and then double check the filesystem type if there's something strange. Years ago there was a bug with ntfs-3g corrupting files, maybe it's something similar (obviously not ntfs because we are on OS X)

Answer 2

I have no experience with DT on IOS, but I think you may have done a union mount .

If that is the case, the solution would be to move files or mount point so that files won't be shadowed.

This article may be relevant: