Tired of backup, wipe, flash, backup, wipe, restore, ... just to try a different ROM?
Today we will cook a nice tasty dual-boot for the TF700T. You will have two separate environments with different ROMs, apps and data that share only the common Linux kernel binary.
Difficulty: medium. No programming skills required, but not for noobs.
Ingredients
1 TF700T running a rooted stock-based ROM with busybox and a kernel with preinit support (hint: -that kernels work fine )
1 PC running Linux with a microSD card reader
1 fast microSD card with at least 4 GB
1 CyanogenMod 10.2 nightly ZIP (should also work for other ROMs - post your results)
1 seasoned chef
Time required: about 30 to 45 minutes.
Directions
Preheat oven to 220 degree celsius ... oops, wrong recipe.
If done right, the internal ROM and its data are perfectly safe. But I assume you have a backup nevertheless - don't blame me if anything goes wrong.
Prepare the microSD card
Insert microSD card into PC card reader. Using gparted, create and format 3 primary partitions:
p1: fat32, this will be your external sdcard as before.
p2: ext4, this will become /data
p3: ext4, this will become /system
Make sure to align the partitions to MiB, or even better multiples of 4 MiB. This may improve I/O performance.
In most cases you can simply shrink the existing FAT32 partition and then create the remaining ext4 partitions.
Partition 3 should be 700 to 800 MB - anything bigger is a waste of space, and anything smaller than 500 MB might cause problems.
Partition 2 will be your whole "internal storage" for the second operating system, so size it according to your storage needs for apps, app data and the emulated /sdcard.
I am using a Samsung 16 GB card with the following partition sizes:
p1: ~ 8 GB
p2: ~ 6 GB
p3: ~ 800 MB
Prepare the new ROM
Before installing the second ROM to the microSD card, the ZIP file must be slightly modified. I assume you know how to unpack and repack a ZIP file and how to use a text editor - if not, find a tutorial elsewhere. .
Note: This step can now be automated, see http://forum.xda-developers.com/showpost.php?p=47333729&postcount=31
To do it manually:
First, extract boot.blob and set it aside for later. Then carefully remove it from the ZIP. Second, find META-INF/com/google/android/updater-script and modify it:
Replace all occurrences of mmcblk0p1 with mmcblk1p3. I had 3 occurrences in CM's updater-script - make sure you modify all of them, otherwise your internal ROM might not survive the installation. This change will redirect the installation to the external microSD card. Finally, remove the line that says package_extract_file("boot.blob", ...) near the end - it would overwrite the kernel and we don't want that.
Now we need to add the WiFi modules. These are compiled directly into the CM kernel, but separate modules in the stock kernel.
Get the kernel modules from your running ROM - they are in /system/lib/modules (e.g. using adb pull /system/lib/modules), and copy at least these two into the ZIP into /system/lib/modules:
cfg80211.ko
bcmdhd.ko (note: for TF300, I think you need bcmdhd_29.ko instead)
Finally, repack the ZIP, mount the first partition of your microSD card and copy the ZIP file there.
Extract the ramdisk files
Note: This step can now be automated, see http://forum.xda-developers.com/showpost.php?p=47333729&postcount=31
To do it manually:
Here comes the tricky part. You need to extract the ramdisk from the boot.blob you saved from the ZIP file in the previous step.
To do that, you need tools that may not be in every household, but should be easy to find using your favorite search engine. In case you have trouble finding and/or compiling them, you can find the result of this step in post #2.
First we need to unpack the blob (https://github.com/AndroidRoot/BlobTools):
Code:
blobunpack boot.blob
This will create boob.blob.LNX. This is the boot image, from which we need to extract the ramdisk (https://github.com/huaixzk/unpackbootimg):
Code:
unpackbootimg -i boot.blob.LNX
This will create several files, we are interested in boot.blob.LNX-ramdisk.gz - copy this one to your tablet, e.g. into /sdcard. For example:
Code:
adb push boot.blob.LNX-ramdisk.gz /sdcard/
Prepare the preinit script and the ramdisk files
Note: This step can now be automated, see http://forum.xda-developers.com/showpost.php?p=47333729&postcount=31
To do it manually:
On the tablet, open a shell in a terminal app or use adb shell and become root (su). Run the following commands:
Code:
mount -o remount,rw /system
cd /system
mkdir boot
cd boot
mkdir rootfs_cm
cd rootfs_cm
gzip -d -c /sdcard/boot.blob.LNX-ramdisk.gz | cpio -i
The first line makes /system writable until the next reboot. The next few lines are self-explanatory. The last line uncompresses the ramdisk image we created in the previous step and extracts the contained files. We are doing this on the tablet itself to preserve the file permissions.
Now modify the file fstab.cardhu (one of the files just extracted).
Replace mmcblk0p1 with mmcblk1p3 and mmcblk0p8 with mmcblk1p2.
mmcblk0p2 can stay as it is, it's the /cache partition that is only used to communicate with the recovery.
Next we need to make sure the WiFi modules that we added are loaded at boot time. Edit init.cardhu.rc and find the "on boot" line. Add below (indentation is important):
Code:
insmod /system/lib/modules/cfg80211.ko
insmod /system/lib/modules/bcmdhd.ko
Near the end of init.cardhu.rc is another reference to mmcblk0p8 that needs to be modified to mmcblk1p2 - near "service setup_fs".
Finally create the file /system/boot/preinit with the following content:
Code:
#!/system/bin/sh
# preinit: only /sys and /system are mounted (ro), / is still rw
PATH=/sbin:/system/bin:/system/xbin
# auto-detect rom2sd
if [ -d /sys/block/mmcblk1/mmcblk1p3 ]; then
echo "\nsystem/boot/preinit: mmcblk1p3 detected, setting up for ROM2SD.\n"
cp -a /system/boot/rootfs_cm/* /
fi
Make sure to make it executable:
Code:
chmod 744 /system/boot/preinit
This script is run by the kernel before the real Android init. It. detects if a microSD card with 3 partitions is inserted, and if yes, it copies the files for the CM root filesystem into the ramdisk. The following Android boot procedure will then mount /system and /data to the partitions on the microSD card and the whole operating system will run from the microSD card. If no card is inserted, nothing is modified and the normal internal ROM is started.
Flashing the ROM
Insert your microSD card into the tablet, boot to TWRP and flash your modified ZIP as usual - but disable signature checking because we didn't sign the modified ZIP.
Recovery
The recovery doesn't know about the external ROM, so you can't use the recovery to backup or restore its system or data. I prefer using the PC for that anyway.
Booting
To boot from internal storage, make sure the microSD card is not inserted when you start the tablet (you can insert it as soon as the boot animation appears). To boot from the microSD card, make sure it is inserted before you turn the tablet on.
That's all. Add more microSD cards for triple-boot, quad-boot, etc.
Notes
My kernel currently has not enabled SELINUX in the config, but CM appears to work anyway.
Update: -that6 enables SELinux.
Shortcut
In case you don't want to extract the CM ramdisk from the blob yourself (or you have trouble finding/compiling the tools to do so), you can try using mine - from my unofficial build of cm-10.2-20131024: View attachment boot.blob.LNX-ramdisk.gz
Automated solution
See http://forum.xda-developers.com/showpost.php?p=47333729&postcount=31
(reserved for additions)
_that said:
Tired of backup, wipe, flash, backup, wipe, restore, ... just to try a different ROM?
Today we will cook a nice tasty dual-boot for the TF700T. You will have two separate environments with different ROMs, apps and data that share only the common Linux kernel binary.
Difficulty: medium. No programming skills required, but not for noobs.
Ingredients
1 TF700T running a rooted stock-based ROM with busybox and a kernel with preinit support (hint: -that kernels work fine )
1 PC running Linux with a microSD card reader
1 fast microSD card with at least 4 GB
1 CyanogenMod 10.2 nightly ZIP (should also work for other ROMs - post your results)
1 seasoned chef
Time required: about 30 to 45 minutes.
Directions
Preheat oven to 220 degree celsius ... oops, wrong recipe.
If done right, the internal ROM and its data are perfectly safe. But I assume you have a backup nevertheless - don't blame me if anything goes wrong.
Prepare the microSD card
Insert microSD card into PC card reader. Using gparted, create and format 3 primary partitions:
p1: fat32, this will be your external sdcard as before.
p2: ext4, this will become /data
p3: ext4, this will become /system
Make sure to align the partitions to MiB, or even better multiples of 4 MiB. This may improve I/O performance.
In most cases you can simply shrink the existing FAT32 partition and then create the remaining ext4 partitions.
Partition 3 should be 700 to 800 MB - anything bigger is a waste of space, and anything smaller than 500 MB might cause problems.
Partition 2 will be your whole "internal storage" for the second operating system, so size it according to your storage needs for apps, app data and the emulated /sdcard.
I am using a Samsung 16 GB card with the following partition sizes:
p1: ~ 8 GB
p2: ~ 6 GB
p3: ~ 800 MB
Prepare the new ROM
Before installing the second ROM to the microSD card, the ZIP file must be slightly modified. I assume you know how to unpack and repack a ZIP file and how to use a text editor - if not, find a tutorial elsewhere. .
First, extract boot.blob and set it aside for later. Then carefully remove it from the ZIP. Second, find META-INF/com/google/android/updater-script and modify it:
Replace all occurrences of mmcblk0p1 with mmcblk1p3. I had 3 occurrences in CM's updater-script - make sure you modify all of them, otherwise your internal ROM might not survive the installation. This change will redirect the installation to the external microSD card. Finally, remove the line that says package_extract_file("boot.blob", ...) near the end - it would overwrite the kernel and we don't want that.
Now we need to add the WiFi modules. These are compiled directly into the CM kernel, but separate modules in the stock kernel.
Get the kernel modules from your running ROM - they are in /system/lib/modules (e.g. using adb pull /system/lib/modules), and copy at least these two into the ZIP into /system/lib/modules:
cfg80211.ko
bcmdhd.ko
Finally, repack the ZIP, mount the first partition of your microSD card and copy the ZIP file there.
Extract the ramdisk files
Here comes the tricky part. You need to extract the ramdisk from the boot.blob you saved from the ZIP file in the previous step.
To do that, you need tools that may not be in every household, but should be easy to find using your favorite search engine.
First we need to unpack the blob (https://github.com/AndroidRoot/BlobTools):
Code:
blobunpack boot.blob
This will create boob.blob.LNX. This is the boot image, from which we need to extract the ramdisk (https://github.com/huaixzk/unpackbootimg):
Code:
unpackbootimg -i boot.blob.LNX
This will create several files, we are interested in boot.blob.LNX-ramdisk.gz - copy this one to your tablet, e.g. into /sdcard. For example:
Code:
adb push boot.blob.LNX-ramdisk.gz /sdcard/
Prepare the preinit script and the ramdisk files
On the tablet, open a shell in a terminal app or use adb shell and become root (su). Run the following commands:
Code:
mount -o remount,rw /system
cd /system
mkdir boot
cd boot
mkdir rootfs_cm
cd rootfs_cm
gzip -d -c /sdcard/boot.blob.LNX-ramdisk.gz | cpio -i
The first line makes /system writable until the next reboot. The next few lines are self-explanatory. The last line uncompresses the ramdisk image we created in the previous step and extracts the contained files. We are doing this on the tablet itself to preserve the file permissions.
Now modify the file fstab.cardhu (one of the files just extracted).
Replace mmcblk0p1 with mmcblk1p3 and mmcblk0p8 with mmcblk1p2.
mmcblk0p2 can stay as it is, it's the /cache partition that is only used to communicate with the recovery.
Next we need to make sure the WiFi modules that we added are loaded at boot time. Edit init.cardhu.rc and find the "on boot" line. Add below (indentation is important):
Code:
insmod /system/lib/modules/cfg80211.ko
insmod /system/lib/modules/bcmdhd.ko
Near the end of init.cardhu.rc is another reference to mmcblk0p8 that needs to be modified to mmcblk1p2 - near "service setup_fs".
Finally create the file /system/boot/preinit with the following content:
Code:
#!/system/bin/sh
# preinit: only /sys and /system are mounted (ro), / is still rw
PATH=/sbin:/system/bin:/system/xbin
# auto-detect rom2sd
if [ -d /sys/block/mmcblk1/mmcblk1p3 ]; then
echo "\nsystem/boot/preinit: mmcblk1p3 detected, setting up for ROM2SD.\n"
cp -a /system/boot/rootfs_cm/* /
fi
Make sure to make it executable:
Code:
chmod 744 /system/boot/preinit
This script is run by the kernel before the real Android init. It. detects if a microSD card with 3 partitions is inserted, and if yes, it copies the files for the CM root filesystem into the ramdisk. The following Android boot procedure will then mount /system and /data to the partitions on the microSD card and the whole operating system will run from the microSD card. If no card is inserted, nothing is modified and the normal internal ROM is started.
Flashing the ROM
Insert your microSD card into the tablet, boot to TWRP and flash your modified ZIP as usual - but disable signature checking because we didn't sign the modified ZIP.
Recovery
The recovery doesn't know about the external ROM, so you can't use the recovery to backup or restore its system or data. I prefer using the PC for that anyway.
Booting
To boot from internal storage, make sure the microSD card is not inserted when you start the tablet (you can insert it as soon as the boot animation appears). To boot from the microSD card, make sure it is inserted before you turn the tablet on.
That's all. Add more microSD cards for triple-boot, quad-boot, etc.
Click to expand...
Click to collapse
It is a nice detail instruction for new users like me. I really like it a lot and I can use some information from your post for my system2sd... However, maybe I misread your post. I don't see any information about repack the blob when you are done modifying the fstab.cardhu. I know a little bit of ramdisk and can get around it but that information will help the first time users... Just my opinion and thanks for sharing a valuable information to us...
LetMeKnow said:
However, maybe I misread your post. I don't see any information about repack the blob when you are done modifying the fstab.cardhu.
Click to expand...
Click to collapse
That's because you don't need to repack the blob or reflash the kernel - I wanted to simplify the procedure, so I added preinit support to the kernel's ramdisk a few months ago. You just put some files in /system/boot and the kernel will run your preinit script that modifies the ramdisk at boot time.
Just remember that if you reflash your internal ROM, you have to recreate the /system/boot stuff.
_that said:
That's because you don't need to repack the blob or reflash the kernel - I wanted to simplify the procedure, so I added preinit support to the kernel's ramdisk a few months ago. You just put some files in /system/boot and the kernel will run your preinit script that modifies the ramdisk at boot time.
Just remember that if you reflash your internal ROM, you have to recreate the /system/boot stuff.
Click to expand...
Click to collapse
Oop, I forgot that you use it in your boot folder... It is my bad.. I will give it a try when I am done with my system2sd testing and will ask more questions on the way.. Thanks for the information...
Cheers,
LMK
_that said:
Notes
My kernel currently has not enabled SELINUX in the config, but CM appears to work anyway.
(reserved for additions)
Click to expand...
Click to collapse
You should be fine until I enforce SELINUX. But I haven't finished the policies yet. Still have some issues to iron out with that. Have about 90% of them done, I think.. lol
Just out of curiosity, will this only work with primary partitions?
johnlgalt said:
Just out of curiosity, will this only work with primary partitions?
Click to expand...
Click to collapse
It should also work with logical partitions if you modify the partition numbers accordingly. And please remove the full quote of my guide from your post, we should not emulate an Outlook-style mess in the forum.
Sent from my ASUS Transformer Pad TF700T using Tapatalk 4
_that said:
It should also work with logical partitions if you modify the partition numbers accordingly. And please remove the full quote of my guide from your post, we should not emulate an Outlook-style mess in the forum.
Sent from my ASUS Transformer Pad TF700T using Tapatalk 4
Click to expand...
Click to collapse
Yeah, I quoted it that way b/c I was asking specifically about that part - but it that part works I suppose the rest would too, huh? :silly:
Wow
Thx for this, easy cheesey, Great work, Love the dual boot!!!!
_that said:
Tired of backup, wipe, flash, backup, wipe, restore, ... just to try a different ROM?
Today we will cook a nice tasty dual-boot for the TF700T. You will have two separate environments with different ROMs, apps and data that share only the common Linux kernel binary.
Click to expand...
Click to collapse
Is there any chance *someone with the required skills* could port bootmanager to our device?
BootManager
it would be the best, considering that your method uses the same load-from-sdcard thing.
Just curious thats all.
kali113 said:
Is there any chance *someone with the required skills* could port bootmanager to our device?
BootManager
it would be the best, considering that your method uses the same load-from-sdcard thing.
Just curious thats all.
Click to expand...
Click to collapse
Looks like commercial software, so ask the devs of that app.
Here is an experimental flashable zip file that redirects the TWRP recovery to the ROM2SD environment. It doesn't really install anything to storage, it just reconfigures the device nodes so that the recovery is tricked into accessing the system and data partitions on the microSD card instead of internal storage.
It works so well that after "installing" this, a following ROM install that unmounts and formats /system and installs itself to /system on mmcblk0p1 will actually be installed on the microSD card, so you don't need to replace the partition names in the updater-script any longer (but you still need to comment out the blob flashing line for now or reflash my kernel after the ROM).
It also works so well that after "installing" this, you don't see your internal /sdcard any longer, so put whatever you want to flash on the first partition of the external microSD card.
"Installing" the script again will undo its actions, so you can toggle back and forth between external and internal storage.
Warning: I tested this only once, and the script does not have any error handling - if the inserted microSD is not prepared for ROM2SD, behavior is undefined - most likely the recovery will complain that it can't mount system or data. Use this at your own risk and make sure you have backed up all valuable data and your ROM, just in case.
View attachment dev-rom2sd.zip
The script also contains a nice example how to output text from a shell script to the recovery console. It shows a list of device nodes so you can see what the script did (the device numbers of mmcblk0p1 and mmcblk1p3 are identical).
Can I follow this guide to have paranoid rom on internal and cromi-x rom on microsd?
vnphatbuddha said:
Can I follow this guide to have paranoid rom on internal and cromi-x rom on microsd?
Click to expand...
Click to collapse
I've never tried PA but it may work if you use my kernel and modify the preinit script accordingly (my kernel contains a stock-compatible ramdisk, so you need to copy the PA ramdisk to / if the microSD is *not* inserted).
_that said:
I've never tried PA but it may work if you use my kernel and modify the preinit script accordingly (my kernel contains a stock-compatible ramdisk, so you need to copy the PA ramdisk to / if the microSD is *not* inserted).
Click to expand...
Click to collapse
sorry for such a noob question but how do you compile the zips from the git links to an executable? Or does the bloobtool and unpackbootimg able to run from its extracted zips? slightly new to this...
vnphatbuddha said:
sorry for such a noob question but how do you compile the zips from the git links to an executable? Or does the bloobtool and unpackbootimg able to run from its extracted zips? slightly new to this...
Click to expand...
Click to collapse
You need to compile the blobtools on git. extract the .zip and run blobunpack on the .blob then abootimg -x on the boot.img.to repack: abootimg --create *new-bootimg* - k *zImage* -r *ramdisk*, then repack the .blob
and/or
follow this tutorial from the blob master himself http://forum.xda-developers.com/showpost.php?p=36925180
JoinTheRealms said:
You need to compile the blobtools on git. extract the .zip and run blobunpack on the .blob then abootimg -x on the boot.img.to repack: abootimg --create *new-bootimg* - k *zImage* -r *ramdisk*, then repack the .blob
and/or
follow this tutorial from the blob master himself http://forum.xda-developers.com/showpost.php?p=36925180
Click to expand...
Click to collapse
The problem I'm having is that I do not know how to use git to compile. What are the commands and do I input it in the top search bar of the site?
vnphatbuddha said:
The problem I'm having is that I do not know how to use git to compile. What are the commands and do I input it in the top search bar of the site?
Click to expand...
Click to collapse
You don't use git to compile, you use it to manage the source code.
To compile the source code, you need the appropriate development tools installed (I think it's called "build-essential" on Debian-like distributions) and run "make" in the directory with the extracted source code.
_that said:
You don't use git to compile, you use it to manage the source code.
To compile the source code, you need the appropriate development tools installed (I think it's called "build-essential" on Debian-like distributions) and run "make" in the directory with the extracted source code.
Click to expand...
Click to collapse
Wow this is too complicated to compile, having to setup and run debian on usb. Guess I can't try out rom2sd