Unbricking the Beaglebone Black

Sometimes bad things happen. In my case my BBB refused to reboot. I have been sloppy about doing clean shutdowns, and I put the blame there. I should not just be pulling the power cord to reboot the system, this is linux after all, even if it is running on eMMC solid state memory. In any event, right now it is displaying both the USR1 and USR3 leds on solid, which supposedly indicates both eMMC activity and uSD activity -- and I have no uSD card. And they stay this way indefinitely.

What I would like to do is to put a runnable system on a uSD drive, plug it into the BBB, boot it, mount the sick system, see if an fsck or some such will fix it. At any rate, I want to copy some files off of it and then reinstall with the latest copy of Angstrom linux.

On the "latest images" link for the BBB is a "non-flasher" image. It is pretty big (almost 4G when decompressed). I have a 16G uSD card. I put it in a card reader and it shows up on my system as /dev/sdb. 

xz -d Angstrom-Cloud9-IDE-GNOME-eglibc-ipk-v2012.12-beaglebone-2013.06.20.img.xz
su
dd bs=10k if=Angstrom-Cloud9-IDE-GNOME-eglibc-ipk-v2012.12-beaglebone-2013.06.20.img of=/dev/sdb
After doing this, there are two partitions on the uSD card (and a lot of free unpartitioned space) Note that this suggests that the size of the image could be reduced significantly given that only about 1/3 of the 3.4G Angstrom image is actually being used. If this was trimmed back, it would be just over 1G in size.

Some comments on "dd"

You want to be very careful that /dev/sdb is the right drive. For example if I made a typo and typed "sda" instead, this would completely wipe out the linux system I am doing this on.

It has been said that the bs= parameter serves no purpose on modern versions of "dd", but my tests tell me otherwise. I find that when I add the parameter "bs=10k" that the copy goes almost 10 times faster.

The copy does take a long time -- almost 20 minutes when I use the bs=10k parameter. It would take around 200 minutes without it (over 3 hours).

Using the recovery card

What you do is to insert this uSD card into the BBB (with the power turned off). Then depress the "boot" button and continue holding it down while applying power. This then boots the Angstrom image on the uSD card. The filesystems on the main BBB (the on board eMMC image) get mounted as /media/Angstrom and /media/BEAGLEBONE. The mount at /media/Anstrom was what I wanted. 
su
cd /media/Angstrom/home/tom
tar cvf backup.tar .
scp backup.tar user@myserver:
Things look fine in the Angstrom filesystem - I have no idea why it won't boot.
Feedback? Questions? Drop me a line!

Tom's Computer Info / tom@mmto.org