dotnet core File.Move issue

Question

My Dockerfile is this

FROM mcr.microsoft.com/dotnet/core/runtime:3.0

COPY publish/ app/
RUN mkdir -p /in
RUN mkdir -p /tmp

ENTRYPOINT ["dotnet", "app/Watcher.dll"]

and I build image with this command

docker build -t watcher/sl_user_test:1.1 .

so, my docker-compose is this

watcher.sl_user_test:
  image: watcher/sl_user_test:1.1
  container_name: watcher_sl_user_test
  build: .
  restart: always
  volumes:
    - /var/storage/in:/in:z
    - /var/storage/tmp:/tmp:z

In my dotnet core app I get a file in the /in folder and I move it to /tmp/aaa code is this

string destination = $"/tmp/{Guid.NewGuid()}/git.zip";
new FileInfo(destination).Directory.Create();
File.Move("/in/git.zip", destination, true);

the problem is that this command copy file and doesn't move it, why? If I go inside the container I can do mv from bash and it works

Can you use File.Delete on the original file? What does File.GetAttributes return? Can the same program read the source of the moved file? — Euphoric, Nov 21 '19 at 15:47

Matt Johnson-Pint · Answer 1 · 2019-11-21T19:04:39.087

1

Since you are creating a new GUID in the path, the directory is guaranteed to not exist already. Thus File.Move will throw a DirectoryNotFoundException.

Create it before you move the file.

var tmpDir = $"/tmp/{Guid.NewGuid()}";
Directory.CreateDirectory(tmpDir);
File.Move("/in/git.zip", $"{tmpDir}/git.zip", true);

Assuming you are doing that, if the File.Move method just does a copy instead of a move, then it is likely that the original file is in use. From the docs (in the Remarks section):

If you try to move a file across disk volumes and that file is in use, the file is copied to the destination, but it is not deleted from the source.

edited Nov 21 '19 at 19:04

answered Nov 21 '19 at 18:59

Matt Johnson-Pint

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This is a good tips, but I use this function to verify if file is in use, and always isn't lock https://stackoverflow.com/questions/876473/is-there-a-way-to-check-if-a-file-is-in-use – Mauro Sala Nov 22 '19 at 14:38
If I run the application directly (without docker) File.Move works – Mauro Sala Nov 22 '19 at 15:16

score 0 · Accepted Answer · answered Nov 25 '19 at 09:29

The problem is that I'm trying to move file from a volume to another. If you try this code in GoLang you receive this error

"rename /dir1/test.txt /dir2/test.txt: invalid cross-device link"

So, the solution are

write your own FileMove function (with copy and delete source)
use only one volume

So, in my case, from this

volumes:
  - /var/storage/in:/in:z
  - /var/storage/tmp:/tmp:z

I'll do this

volumes:
  - /var/storage/data/:/data:z

and in /data there are "in" and "tmp" folders

dotnet core File.Move issue

2 Answers2