CODEWITHSUNDEEP
windowsdockerwindows-subsystem-for-linux
tweetysat
tweetysat

Reputation: 2403

Docker mounted volumes remains sometimes empty

Perhaps I'm missing something stupid but there is something I don't understand.

If I do docker run -d --name test -v ~/test-log:/var/log/nginx -v ~/test-config:/etc/nginx/conf.d nginx:latest

I've got

ls -l ~/test-log
total 0
-rw-r--r-- 1 root root 0 Sep  1 11:17 access.log
-rw-r--r-- 1 root root 0 Sep  1 11:17 error.log

But

ls -l ~/test-config
total 0

However without any mounts /etc/nginx/conf.d is not empty

docker run --rm --name test2  nginx:latest ls -l /etc/nginx/conf.d
total 4
-rw-r--r-- 1 root root 1093 Aug 11 14:50 default.conf

So why files in /var/log/nginx are well present in ~/test-log while ~/test-config remains empty and moreover /etc/nginx/conf.d becomes empty ?

What am I missing ?

Upvotes: 1

Views: 339

Answers (1)

BMitch
BMitch

Reputation: 264236

Volumes mount files/directories from the source over whatever exists inside the image at that location. You no longer see the image contents when a mount replaces access to that directory, same a mounting a filesystem other ways in Linux.

Named volumes in Linux are a semi exception because docker initializes the contents of a named volume with the image directory contents. This does not apply to host volumes like you are using.

Once the volume is mounted, files are created/modified/deleted by the application running inside the container. In this case, that app creates logs, but it does not write it's own configuration files.

Upvotes: 1

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