U-Boot# printenv snappy_ab
snappy_ab=b
U-Boot# printenv snappy_mode
snappy_mode=try
U-Boot# reset
resetting ...

U-Boot SPL 2015.07-dirty (Jul 17 2015 - 11:40:49)
MMC: block number 0x100 exceeds max(0x0)
MMC: block number 0x200 exceeds max(0x0)
*** Error - No Valid Environment Area found
*** Warning - bad CRC, using default environment



U-Boot 2015.07-dirty (Jul 17 2015 - 11:40:49 +0200)

       Watchdog enabled
I2C:   ready
DRAM:  512 MiB
MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
reading uboot.env
Net:   <ethaddr> not set. Validating first E-fuse MAC
cpsw, usb_ether
Hit any key to stop autoboot:  0 
switch to partitions #0, OK
mmc0 is current device
SD/MMC found on device 0
reading boot.scr
** Unable to read file boot.scr **
reading uEnv.txt
0 bytes read in 4 ms (0 Bytes/s)
Loaded environment from uEnv.txt
Importing environment from mmc ...
Running uenvcmd ...
reading a/vmlinuz
6517648 bytes read in 386 ms (16.1 MiB/s)
reading a/initrd.img
13546197 bytes read in 797 ms (16.2 MiB/s)
reading a/dtbs/am335x-boneblack.dtb
30025 bytes read in 13 ms (2.2 MiB/s)
Kernel image @ 0x82000000 [ 0x000000 - 0x637390 ]
## Flattened Device Tree blob at 88000000
   Booting using the fdt blob at 0x88000000
   Loading Ramdisk to 8f314000, end 8ffff2d5 ... OK
   Loading Device Tree to 8f309000, end 8f313548 ... OK

Starting kernel ...