FunionFS

[levi]

Has anyone used FunionFS on the Pandora? As I understand it, the Pandora kernel is new enough to support FUSE filesystems, and FunionFS is a FUSE file system to give you union filesystems. A union filesystem allows you to mount two or more directories or filesystems in the same place, and for writes to only go to one of the filesystems, with reads coming from the read-only file system initially, or if there's a version of the file on the writable filesystem, on there instead. Other union filesystems let you do more fancy things like load balancing, but FunionFS seems simpler (and actually has legible instructions, which is novel).


I think it would be cool if you could use it on the Pandora to mount the whole NAND as read only and mount a directory on your SD card on top, so you are able to change anything you like (other than the kernel image and a few other things I guess), and install cool little scripts to /usr/bin and so on without worrying - although of course you'd need to install FunionFS to the NAND and the mount command to enable it.


Of course, you could just install the OS to your SD card and boot off that, but I'm curious as to whether it's worth using a union filesystem (as most linux live CDs do) to save SD card space, and what the speed penalty is.

 

[sebt3]

Union FS are used within the PND system, so it does work here

 

[urjaman]

Union FS are used within the PND system, so it does work here

Yeah, but that is AUFS, not FunionFS. Which brings the question, why would you want FunionFS when we already have AUFS in the kernel?

 

[Eridger]

I'd love a feature like this. I'm not entirely sure how the PND system works, but something like this would make me feel much better about testing programs before packing them into a PND. At least, I think it would make me feel better, anyways.

 

[urjaman]

something like this would make me feel much better about testing programs before packing them into a PND.

IIRC originally the PND system worked also with unpacked PNDs eg. directories containing a PXML.xml file. OTOH it's possible that this has broken along the way. Anyhows, its not like its that hard to do the equivalent setup manually. Just create the appdata folder and /mnt/utmp/folder and union-mount the appdata as rw and your base folder as ro into the utmp folder. Then run your app from the utmp folder.

 

[Eridger]

something like this would make me feel much better about testing programs before packing them into a PND.

IIRC originally the PND system worked also with unpacked PNDs eg. directories containing a PXML.xml file. OTOH it's possible that this has broken along the way. Anyhows, its not like its that hard to do the equivalent setup manually. Just create the appdata folder and /mnt/utmp/folder and union-mount the appdata as rw and your base folder as ro into the utmp folder. Then run your app from the utmp folder.

Sounds simple enough. Thanks!