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README: primordial documentation on booting from the external microSD card

feature/booting-external-microsd
Fivel Sotheby 2018-09-01 22:01:09 +01:00
parent 2c253e5bec
commit 5347c41ac6
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README.md
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@ -136,7 +136,49 @@ sync
Booting from the external microSD card
--------------------------------------
TODO
* Insert the external microSD card in the ereader and boot it up.
* Get a shell on the device, either via Telnet, SSH or some sort of terminal emulator.
* On the ereader shell, mount the rootfs as read only and clone the internal memory into the external microSD card:
```
umount /mnt/onboard
mount -o remount,ro /
dd if=/dev/mmcblk0 of=/dev/mmcblk1
```
* Remount the filesystems with their default options:
```
mount -o remount,rw /
mount -t vfat -o noatime,nodiratime,shortname=mixed,utf8 /dev/mmcblk0p3 /mnt/onboard
```
* Remove the microSD card from the ereader and insert it into a computer with a microSD card reader.
* Extract the hardware configuration block from the microSD card. For example, on a GNU/Linux computer, assuming the SD card is at /dev/mmcblk0 (replace as needed):
```
dd bs=512 skip=1024 count=1 if=/dev/mmcblk0 of=ereader.hwconfig
```
* Use a hex editor to change the byte at offset 0x3F (63) from 0 to 1:
```
printf '\x01' | dd of=ereader.hwconfig bs=1 seek=63 count=1 conv=notrunc
```
* Write it back to the microSD card
```
dd if=ereader.hwconfig bs=512 seek=1024 of=/dev/mmcblk0
```
* Proceed with the installation as documented in **Installation on the internal microSD**.
* Hold down the power and backlight buttons while booting until the LED is blinking to boot from the external microSD card.
Notes for developers