Launch Linux without vnc

I'm new to the forum so please pardon me if my english or explainations are not perfect.
I post here to explain a way to launch linux from android without vnc.

We need to stop android services to do that, but as already explain in other topics, the framebuffer access seems to be blocked on android 4.4 (or above).
I found that the framebuffer can still be accessed but just at the beginning of the boot process.
A way to launch linux is thus to modify the file "/system/etc/install-revovery.sh" (sometimes it is under "/system/bin") wich is started just at the same moment with other android services.
You can for instance add in that file:

busybox mount /dev/block/mmcblk1p1 /mnt/asec
# were mmcblk1p1 is your sdcard
if [ -e /mnt/asec/start.sh ] ; then
setprop ctl.stop zygote
setprop.ctl.stop bootanim
setprop ctl.stop surfaceflinger
setprop ctl.stop servicemanager
# (you should stop all services showed in /init.rc that restart other services)
# (you can repeat the setprop ctl.stop two or three times to be sure they are stopped)
exec busybox chroot /mnt/asec /start.sh
fi

In your sdcard, you should install a linux-arm system (for instance debian, can be done with linuxdeploy app), and place a file "start.sh" like this one:

export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
mount -t tmpfs none /dev
mount -t proc none /proc
mount -t sysfs none /sys
sleep 1
busybox mdev -s
# (busybox should be installed in the linux-arm system)
mkdir /dev/pts
mount -t devpts none /dev/pts
sleep 1
sudo startx -- vt1

If you reboot your device within your sdcard insert, linux should start. If something goes wrong, just reboot the device without the sdcard (long-press power), and android should restart.
If your kernel doesn't have tty support, it can also work. Just add in the "install-recovery.sh" file:

( while [ 1 ]
do
echo 0>/sys/class/graphics/fb0/rotate
busybox sleep 0.01
done ) &

And in your start.sh you should replace the last line with:

ln -s /dev/null /dev/tty1
sudo startx -- vt1 -sharevts

(I learn this trick by examin the source code of linuxdeploy, wich use it too).

If you're lucky, touchscreen will work (with default evdev driver that comes with linux).
If not, you can try tslib driver (search for "tslib" and "xf86-input-tslib" on olimex website or other places on the web).
For this be aware they are some patchs to apply (can be found on olimex website) and you should compile.
However when sucessfull it seems to work on a good number of devices (you can also try some "tslib-multitouch" patchs that make the driver work on some other devices).
For the keyboard you can use matchbox-keyboard program for instance, wich use the touchscreen to emulate the keyboard.

I've tested this method on two tablets (an allwinner and a rockchip) and on a Wiko phone (MediaTek processor). It has worked for each of three.
Be carefull nevertheless when modifying "install-recovery.sh" (wrong manipulations can brick your device, you are warned, I shall not be responsable for any damage).

Thanks.

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