Comex Got Unionfs Working, Means Faster Jailbreak Process

It looks iPhone jailbreak star Comex has got yet another success at jailbreak scene, this time Comex has got “Unionfs” working & only thing got to do is to get rid of crashes. Now for end users Unionfs means a faster jailbreak process. Until now stashing approach jailbreaks have been using for years which involved reorganizing Filesystem by Cydia which is not only slow but often takes ages to complete the process and also requires reboot.

Cydia Preparing FileSystemComex has posted the complete explanation of how existing Stashing approach works and advantage of Unionfs over stashing.

“If you don’t know, the stashing approach jailbreaks have been using for years– Cydia’s “Reorganizing Filesystem”– involves moving some large directories from the small / partition into the large /var partition, then creating symlinks from the original to the new location. This both ensures that any additional stuff put in those directories by packages will end up in the /var partition, and frees up space on the / partition for files created outside of those directories. However, the process has some issues, like taking forever to do when you jailbreak (I am a bit fanatical about speed), pretty much requiring the jailbreak to reboot the system to ensure there aren’t any running applications pointing to the old files (ditto about speed, I want a jailbreak to not even require a respiring, as in star, but since star used stashing, some obscure things could cause issues before a reboot), and seriously confusing the sandbox code in the kernel (because each application has a sandbox with a list of allowed filenames, but after the symlink has moved files, the filenames no longer match), requiring that code to be patched (it needs to be patched anyway these days because tweaks have to run under the sandboxes of the applications they’re hooking, but depend on accessing various directories; but it still feels good to get rid of a kludge).

With unionfs (which was saurik’s idea originally), new files are created in the /var partition, and merged with files in the corresponding directories in the / partition, so no files need to be moved, no descriptors are invalidated, and I think the sandbox code won’t notice what happened. It also opens the door for upgrading the base operating system without destroying the jailbreak files (although maybe iOS 5 delta updates will already allow this? I haven’t looked at them yet).

I’ve wanted to do this since literally a year ago (that’s the date of the nullfs checking, since I was dumb and thought I wanted that instead of unionfs), but I never got around to making it work properly.

So, I just hope that I can get rid of the crashes my meddling with unionfs’s code have introduced, and fix it for the iPad 2 (my dumped copies of iPad 2 kernels do not include symbols; I wrote a small BinDiff-like tool to copy over symbols from a kernel for another device, but it’s not perfect) and that there aren’t any performance issues.”

So in next jailbreak from Comex might use this unionfs method that’s when we will see how fast the jailbreak process is due to unionfs. By the way JailbreakMe 3.0 for iPad 2 jailbreak is expected any time soon.

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Stay tuned with is for more information on iPad 2 Jailbreak.



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