[MOD][RECOVERY] Multiboot v2.0 topic

Hi all,

This dev thread is to continue the multiboot thread that I starded few months ago in general section.
To read history of the project you can take a look here http://forum.xda-developers.com/show....php?t=2577211

With Multiboot, you can launch any ROM from your internal card or your external sdcard.
This feature is possible thank's to kexec-hardboot method created by mkasic (http://forum.xda-developers.com/show....php?t=1266827).

I adapted this method to be able to apply it quite easily on any android device.

This method includes few pieces of software ( sources will be published) :

• kexec-hardboot : kernel patch from mkasic


• hardboot-reserve : new kernel patch


• kload-hardboot : new userspace program

Next part of the method is an on the fly modification of initrd ramdisk before injecting new kernel/initrd. Early versions of multiboot (before v1.2) were simply modify [on fs] section of init.rc to replace original block devices ( mmcblk0p14, mmcblk0p15 etc ) by loop devices pointing to img files.
Since Multiboot v1.2, a new method is used to replace original filesystems : a script replace original init binary, his goal is to prepare all the filesytems before launching original init.
All this method is done by shell scripts that you can check in /sbin and /multiboot directories when booted into recovery.


Creating img files (raw) is very efficient on internal sdcard as this card is formatted ext4 and img files can be thin provisiionnig ( sparse files ).
Unfortunaltely, external sdcard are offently fat32 or exfat formated. Those filesystems do not support thin provisionning ( note also that multiboot supprot only vfat for the moment ).
Creating img files on vfat filesystems is very long process and consume lot of space.

New version Multiboot V2.0 introduces a new feature : qcow2 support for external sdcard.
With qcow2 image files, we can create small images which grows only when needed.

You can check some video demonstrating features of multiboot on youtube channel : http://www.youtube.com/channel/UCefO8F4YX6qMQsqpBHTqTqQ

Main advantages of using qcow2 :

• thin provisionning


• snapshots


• compression


• liveboot ( livefull if small rom, "livedvd-like" if bigger roms )

Some problem (and solutions) of qcow2 :

• need target kernel with nbd support - nbd is very easy to activate when compiling kernels but not already activated on kernels. Decimalman kernels already are compiled with it. http://forum.xda-developers.com/show....php?t=2226889


• Slow speed on standard : speed on qcow2 especially when first installation is not good. To reduce this, livesnap booting mode gives very good speed.


• suspend/resume : on tw43 kernels, deepsleep can hang the system. To correct it, their are 2 methods : adding a wakelock or apply a small patch to nbd.c sources.

Some details about qcow2 booting mode :

1. - standard : qcow2 images are acceded read/write directly on sdcard ( not recommended especially in firsts boot )


2. - livesnap : qcow2 images are acceded read, writes are done in zram snapshots. commit are done at reboot time : this is the recommended mod. If you install apps, you'd better to reboot first to commit qcow2. Note that if modifications are big, reboot can be long ( few minutes ), be patient. Note also that in this mode, I added a wakelock to fix suspend/reboot of tw roms.


3. - liveboot : same that livesnap but without commit - Same than a LiveCD in linux world. reboot speed is regular


4. - fulllive : only for small roms ( say ~500M ). All qcow2 are copied to zram at boot and mounted from memory. No internal/external card needed. very good speed.


5. - livesnap2 : same than livesnap but without wakelock. Best for speed and battery. Working except tw43. Download my modified dkp kernel to use this option on tw43 roms.

Important recommendations :

- when choosing qcow2, always choose the right nbd kernel as the last zip to install ( and don't reboot after Aroma installer )

• take dkp kernels for tw43 and kk4.4.2 : http://forum.xda-developers.com/show....php?t=2226889


• or kernels I compiled

- please follow videos on youtube

Here are last video I did to demonstrate qcow2 features. Some parts of video are boring ( during compression or commit ) but I wanted to let it go live to give an idea of processing times.




Downloads : http://www.androidfilehost.com/?w=files&flid=12801

References / Credits :
mkasic : kexec-hardboot creator - http://forum.xda-developers.com/show....php?t=1266827
Tassadar : MultiROM creator - best project - http://forum.xda-developers.com/show....php?t=2011403 - bbootimg used
TWRP Team : http://www.teamw.in/project/twrp2