How to set up a writable file system on a DwarFS image in Windows?

[FirTech]

I want to run programs in a DwarFS image, and many programs require a writable file system. I read in the help document that overlayfs is only applicable to Linux environments. Is there any way to achieve this in Windows environments? Can you add an option to write written files to memory or a folder? I know that DwarFS is a read-only file system, and I just want the program to run.

[silentnoodlemaster]

could you use unified write filter?

[mhx]

I quite honestly have no idea as I'm not using Windows. Please take a look at @silentnoodlemaster's suggestion, this seems reasonable.

If you figure out how to do it, please feel free to post some instructions here or create a PR to update the documentation. :)

[xsmolasses]

Sandboxie-Plus should provide this - met with compatible mount options and settings across the board.

Unified Write Filter (UWF) feature, only Windows Enterprise & Education though, so says Requirements.

Or mess with Rclone, if you can live with a broken rename and quirky delete of static (DwarFS) items.
Barebones .cmd takes [DwarFS] paths, combines all into .\rclone (changes commit ideally to .\writes).

@ECHO OFF

SET "RCLONE_CONFIG=NUL"
SET "RCLONE_CONFIG_dwarfs_TYPE=union"
::SET "RCLONE_CONFIG_dwarfs_SEARCH_POLICY="
::SET "RCLONE_CONFIG_dwarfs_CREATE_POLICY="
::SET "RCLONE_CONFIG_dwarfs_ACTION_POLICY="

SET "RCLONE_CONFIG_dwarfs_UPSTREAMS=".\writes""
FOR %%A IN (%*) DO CALL SET "RCLONE_CONFIG_dwarfs_UPSTREAMS=%%RCLONE_CONFIG_dwarfs_UPSTREAMS%% "%%~A:ro""
REM emit :ro then files can be deleted but quickly repopulate!
REM omit :ro then files remain deleted, while the mount lives?

MKDIR ".\writes" 2>NUL
rclone.exe --cache-dir ".\cached" mount dwarfs: ".\rclone" -oFileSecurity="D:P(A;;FA;;;WD)" --vfs-cache-mode writes --vfs-case-insensitive --vfs-links

EXIT /B

[mhx]

To be fair, it shouldn't be too hard to get something like fuse-overlays or unionfs-fuse to work on Windows with WinFSP, in case none of the other options is viable.

[FirTech]

could you use unified write filter?

I tried using uwf, but it should not work. In the following example, K is the drive letter after DwarFS is mounted
C:\Users\Administrator>uwfmgr volume protect K:
Unified Write Filter Configuration Utility Version 10.0.14393
Copyright (c) Microsoft Corporation. All rights reserved.

Error: Unified Write Filter cannot protect K: (This volume does not contain a recognizable file system.
Please make sure that all requested file system drivers are loaded and that this volume is not damaged.).

[FirTech]

Sandboxie-Plus should provide this - met with compatible mount options and settings across the board.

Unified Write Filter (UWF) feature, only Windows Enterprise & Education though, so says Requirements.

Or mess with Rclone, if you can live with a broken rename and quirky delete of static (DwarFS) items. Barebones .cmd takes [DwarFS] paths, combines all into .\rclone (changes commit ideally to .\writes).

@ECHO OFF

SET "RCLONE_CONFIG=NUL"
SET "RCLONE_CONFIG_dwarfs_TYPE=union"
::SET "RCLONE_CONFIG_dwarfs_SEARCH_POLICY="
::SET "RCLONE_CONFIG_dwarfs_CREATE_POLICY="
::SET "RCLONE_CONFIG_dwarfs_ACTION_POLICY="

SET "RCLONE_CONFIG_dwarfs_UPSTREAMS=".\writes""
FOR %%A IN (%*) DO CALL SET "RCLONE_CONFIG_dwarfs_UPSTREAMS=%%RCLONE_CONFIG_dwarfs_UPSTREAMS%% "%%~A:ro""
REM emit :ro then files can be deleted but quickly repopulate!
REM omit :ro then files remain deleted, while the mount lives?

MKDIR ".\writes" 2>NUL
rclone.exe --cache-dir ".\cached" mount dwarfs: ".\rclone" -oFileSecurity="D:P(A;;FA;;;WD)" --vfs-cache-mode writes --vfs-case-insensitive --vfs-links

EXIT /B

Wow, I tried running Chrome in DwarFS through the Rclone command you gave, and it miraculously worked! But I don’t know if this method will affect other programs, and compatibility needs to be discussed.

[mhx]

Error: Unified Write Filter cannot protect K: (This volume does not contain a recognizable file system. Please make sure that all requested file system drivers are loaded and that this volume is not damaged.).

Interesting. I wonder if this could be because of the way WinFsp advertises the file system to Windows?