Solved -- Running safestrap on sdcard -- looking for input

[blitzkriegoutlaw]

So I got tired of my weird configuration of running the apps in a mounts2sd with a second ext4 partition on my sdcard and technically nothing should prevent us from running safestrap on the sdcard. So I looked around and it took me a while but I found Hashcode's source code and spent some time studying all the voodoo he does, and most of it is fairly straight forward. Small breakdown:

* Extend TWRP with ifdef statement to add new buttons
* sh scripts get called to perform the functionality for those button
* Swap out some links in /dev/block when you switch between slots and stock
* The entire boot partition including scripts, TWRP, etc are stored in boot image
* The boot image is stored in the stock system under /etc/safestrap

Like I said before, most of the functionality is done in borne shell scripts, but there is some hardcoding in TWRP like creating the .img file to /ss. I really don't want to try to recompile TWRP at this time. As such, I want to limit my changes to the borne shell and configuration INI files only. The simplest answer is to remap /ss from internal storage to the sdcard storage. Another option is to have "system" and "cache" in the internal storage and moving "data" to the sdcard. The difficulty here is since TWRP is hardcoded to create the .img file under /ss, I need to move it during the format stage which happens in the script. The danger with the first option I don't know if the phone will boot if the sdcard is removed. safestrap looks for that directory to figure out the mappings in /dev/block. I think if the directory is missing then it will attempt to create it. After that, things might go bad.

Anyway, what are your thoughts?

 

[lucky_515]

i wish and hope your still working on this..my phone is so low in internal storage..i cant even use a rom slot other than stock,,ive been useing stock slot ,flashing custom rom in stock slot....anyways hope you continue to figure this out..i know lots of people would appreciate it..thanks

 

[blitzkriegoutlaw]

So I've tried multiple ways and have had to step away, think about it some more, and come back to it. Essentially I was not able to get system to boot off of the sdcard. However, the good news is today I was able to have system and cache on internal storage and data on sdcard. So here are the keys to the kingdom that I have found....

The CM11 (and I assume other) ROMs there is a /system/etc/kexec/ramdisk.img file. This file is extracted (gunzip < ramdisk.img | cpio -iu) into the root directory "/" (rootfs). There is a shell script "/sbin/fixboot.sh" that gets executed by /init at the start of the android (on fs). That script essentially mounts /ss to /emstorage and does all the loop storage links to the system.img, cache.img, and data.img files. I was able to mount another /ss2 to my sdcard and point the userdata to /ss2/safestrap/rom-slot?/userdata.img. The limitation is that vfat limits all files to 4 GB max, so the userdata.img cannot be more than 4 GB of storage.

So an option is I can create an updated ramdisk.img file. You would just drop this into your /system/etc/kexec directory on the slot-rom you want to use it. The only file changed in ramdisk.img is /sbin/fixboot.sh. ramdisk.img is part of the CM11 distribution so you would need to replace it each time you perform an update on that rom slot. Other than that, safestrap would by default create userdata.img to be in internal storage.

The next part I'm going to look at is to create a f2fs partition on my sdcard and have my userdata use that f2fs partition. I figure I should good considerable more I/O as f2fs is suppose to be a good amount faster than ext3/4 and we wouldn't be going through a loop device from ext3 to vfat for all I/O. In addition, my data partition would no longer be limited to 4GB due to the file limitation size of vfat.

Thoughts...

 

[blitzkriegoutlaw]

So Spyder doesn't have f2fs on it so I've been running ext4. The kernel would need to be setup to be compiled with it. I have a second 6Gb partition formatted with ext 4 with writeback journaling but per my timing tests I don't think it has made a difference. Now I have more than enough space left in both the data and internal partitions. I don't know if it is just a placebo effect but my apps do seem to start slightly faster.

There doesn't seem much interest in this but it was a fun exercise for me. This will be good enough for me as I'll probably upgrade my phone sometime in the future.

Sent from my XT912 using XDA Free mobile app