View source for EBC Exercise 22 Recovering

[[Category:ECE497]]
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What do you do if you've been working on the kernel or u-boot and now your BeagleBone Black won't boot? Here's what works if you've saved the .orig files as suggested. If you didn't save the files, goto [[EBC_Exercise_03_Installing_a_Beagle_OS]] and reflash the whole thing, see you in 45 minutes.

If you did make backups, follow along, this is much faster.

== Getting the SD card image ==
The first step is to set up an SD that you can boot off. Before, you created an SD card that would copy an image to the on board eMMC.  This is different, now you will be booting off the SD card.  No need for the 45 minute wait.

Go to the [http://beagleboard.org/latest-images latest images] and download the first link (Angstrom Distribution (BeagleBone, BeagleBone Black - 4GB SD) 2013-06-20).  Copy it to your SD card like you did for the eMMC image.

== Boot off the SD card ==
Once your SD card is ready, 
# power off the Bone
# put SD card in the reader on the Bone
# hold down the '''S2''' button.  It's the one near pin 45 of P8
# power up the bone, while still holding S2
# wait for all the LEDs to light and the release S2.
You are now booting off the SD card.  Once booted, login and mount the eMMC partition.

== Mounting the FAT partition ==
If you are recovering from changing u-boot you need to mount the first (FAT) partition.
 beagle$ '''mkdir /media/BONE'''
 beagle$ '''mount /dev/mmcblk1p''1'' /media/BONE/'''
 beagle$ '''cd /media/BONE/'''
 beagle$ '''ls'''
 App   Drivers  LICENSE.txt  README.md  autorun.inf  u-boot.img.new   uEnv.txt
 Docs  ID.txt   MLO          START.htm  u-boot.img   u-boot.img.orig

You can now move the original u-boot image back
 beagle$ '''rm u-boot.img'''
 beagle$ '''cp u-boot.img.orig u-boot.img'''
 beagle$ '''cd ..'''
 beagle$ '''umount BONE'''

== Mounting the ext4 partition ==
If it's the kernel you need to recover, you need to mount the second (ext4) partition. It's like before, but you change one digit.
 beagle$ '''mkdir /media/BONE'''
 beagle$ '''mount /dev/mmcblk1p''2'' /media/BONE/'''
 beagle$ '''cd /media/BONE/'''
 beagle$ '''ls'''
 bin   dev  home  lost+found  mnt   run   sys  usr
 boot  etc  lib   media       proc  sbin  tmp  var
 beagle$ '''cd boot'''
 beagle$ '''ls'''
 am335x-bone.dtb       omap3-evm.dtb       uEnv.txt
 am335x-boneblack.dtb  omap3-tobi.dtb      uImage
 am335x-evm.dtb        omap4-panda-a4.dtb  uImage-3.8.13
 am335x-evmsk.dtb      omap4-panda-es.dtb  uImage-3.8.13-bone26.1
 am335x-tester.dtb     omap4-panda.dtb     uImage-3.8.13-bone27
 omap2420-h4.dtb       omap4-sdp.dtb       uImage_bak
 omap3-beagle-xm.dtb   omap4-var-som.dtb
 omap3-beagle.dtb      omap5-evm.dtb
 beagle$ '''rm uImage'''
 beagle$ '''ln -s uImage-3.8.13 uImage'''

And then clean up
 beagle$ '''cd ../..'''
 beagle$ '''umount BONE'''

== Rebooting ==
You can't just run the '''reboot''' command at this point.  You need to power off the Bone, remove the SD card and then reboot.
 beagle$ '''halt'''
One the lights are off, eject the SD card and power up.  You should be recovered.

{{YoderFoot}}