I have a few inter-related issues:
- Why would one kernel boot a card that another kernel can't?
- Why would a card's disk geometry matter for boot?
- Who is a good manufacturer for getting hardware-identical cards in bulk?
- How can I probe the actual "disk geometry" of an sd card?
I bought 100 Transcend SD cards a little while ago and duplicated them with an OpenEmbedded-based filesystem (linux-2.6.36).
There were a few "bad" cards that I threw out, but the success rate was acceptable.
In the next round of 40 SD cards I used a Linaro-based filesystem (linux-2.6.39) and had about a 50% failure rate when testing that the cards would boot, which is absurd.
There kernel reports: [ 1.003204] mmcblk0: unknown partition table
However, the cards would mount and show files just fine.
I reduplicated one of the non-booting cards with an OpenEmbedded filesystem and then it booted. Weird!
After some investigation I found that using `gparted` (instead of `fdisk`) to create a new partition table and then `rsync`ing the contents of the original filesystem resulted in a booting Linaro card.
Rinse and repeat and I ended up with 3 images which only vary by the disk geometry as reported by `fdisk -l`:
- 50% -- 255 heads, 63 sectors/track, 974 cylinders
- 40% -- 2 heads, 4 sectors/track, 1957632 cylinders
- 10% -- 247 heads, 62 sectors/track, 1022 cylinders
- 1 card still didn't boot
I'm lost. Please advise.
Non-booting kernel message
[ 0.923309] Waiting for root device /dev/mmcblk0p2...
[ 0.957885] mmc0: host does not support reading read-only switch. assuming write-enable.
[ 0.982025] mmc0: new high speed SDHC card at address b368
[ 0.988494] mmcblk0: mmc0:b368 USD 7.46 GiB
[ 0.993957] mmcblk0: detected capacity change from 0 to 8018460672
[ 1.003204] mmcblk0: unknown partition table
[ 1.036926] VFS: Cannot open root device "mmcblk0p2" or unknown-block(179,2)
[ 1.044433] Please append a correct "root=" boot option; here are the available partitions:
[ 1.053344] b300 7830528 mmcblk0 driver: mmcblk
[ 1.058959] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(179,2)
Booting kernel message
[ 1.122070] mmc0: host does not support reading read-only switch. assuming write-enable.
[ 1.146087] mmc0: new high speed SDHC card at address b368
[ 1.152557] mmcblk0: mmc0:b368 USD 7.46 GiB
[ 1.158020] mmcblk0: detected capacity change from 0 to 8018460672
[ 1.166351] mmcblk0: p1 p2 p3
[ 1.259674] EXT3-fs: barriers not enabled
[ 1.265411] kjournald starting. Commit interval 5 seconds
[ 1.271331] EXT3-fs (mmcblk0p2): mounted filesystem with ordered data mode
[ 1.278686] VFS: Mounted root (ext3 filesystem) readonly on device 179:2.