Note: The information in this article pre-dates our move to cbootimage/tegrarcm and is no longer applicable for BSPs after V2.3 Beta 2 (T30) resp. V2.3 (T20).
The partitioning is done during recovery mode flashing by Fastboot/NvFlash based on the following configuration files contained in our BSP image packages:
apalis-t30_bin/emmc-flash.cfg colibri-t20_bin/lnx_hsmmc.cfg colibri-t30_bin/emmc-flash.cfg
NVIDIA uses a custom partitioning layout which only packs the root file system into a regular GPT (GUID Partition Table). The primary GPT is usually at a offset of 512 KBytes, but this area is used by the boot ROM for the BCT (Boot Configuration Table), PT (Partition Table) resp. boot loader, hence a custom offset is used (see gpt gpt_sector=<offset> kernel boot argument). The secondary GPT is at the end of the block device.
To avoid having to download lots of empty space during flashing our update script calculates a minimal size and generates an ext3 partition accordingly. During first boot, a custom resizing script (/usr/sbin/resizefs.sh) is run which increases the partition size to its full extend.
Edit the configuration file and add your custom UDA partition between the APP and GPT one as follows:
... [partition] name=APP id=9 type=data allocation_policy=sequential filesystem_type=basic size=2048000000 #previously 0xFFFFFFFFFFFFFFFF file_system_attribute=0 partition_attribute=0 allocation_attribute=8 #previously 0x808 percent_reserved=0 filename=APP.ext3 [partition] name=UDA id=10 type=data allocation_policy=sequential filesystem_type=basic size=0xFFFFFFFFFFFFFFFF file_system_attribute=0 partition_attribute=0 allocation_attribute=0x808 percent_reserved=0 # Extensible Firmware Interface (EFI) Secondary GUID Partition Table (GPT) [partition] name=GPT id=11 type=GPT allocation_policy=sequential filesystem_type=basic file_system_attribute=0 partition_attribute=0 allocation_attribute=8 percent_reserved=0
Please note one NvFlash bug setting that last user partitions last sector equal to the secondary GPT equivalent at the very end which will cause the secondary GPT to be overwritten if not paying careful attention to this. Our resize script usually run during first boot takes care of this but adding your own partition you probably want to adjust that behaviour.
Output from Fastboot/NvFlash during flashing:
... SD Alloc Partid=9, start sector=7296,num=1000000 SD Alloc Partid=10, start sector=1007296,num=982592 SD Alloc Partid=11, start sector=1989888,num=0 ... Format partition APP Region=4 SD Erase start 512B-sector=29232,512B-sector-num=3999912 Format partition UDA Region=4 SD Erase start 512B-sector=4029200,512B-sector-num=3930304 Format partition GPT ...
The first partition can now be resized without any danger:
root@colibri-t20:~# resize2fs /dev/mmcblk0p1 3999912s resize2fs 1.42.7 (21-Jan-2013) Filesystem at /dev/mmcblk0p1 is mounted on /; on-line resizing required old_desc_blocks = 1, new_desc_blocks = 1 Performing an on-line resize of /dev/mmcblk0p1 to 499989 (4k) blocks. The filesystem on /dev/mmcblk0p1 is now 499989 blocks long.
According to http://en.wikipedia.org/wiki/GUID_Partition_Table the primary and secondary GPT are 32 (512 byte) blocks each. During creation of the last file system one has to subtract those (divide by 8 due to 512 byte eMMC/SD vs. 4096 byte ext3 block size):
(3930304-32)/8 = 491284
Creating the custom ext3 file system without overwriting the secondary GPT. The block size of 4096 is the default for partitions bigger than 512MB, but set it explicitly to avoid any issues. (careful with ext4 due to a bug in NVIDIA's Linux kernel):
root@colibri-t20:~# mkfs.ext3 -b 4096 /dev/mmcblk0p2 491284 ...
After a reboot that partition even automatically gets mounted to /media/mmcblk0p2 thanks to udev:
root@colibri-t20:~# df Filesystem 1K-blocks Used Available Use% Mounted on /dev/root 1967652 291408 1576932 16% / devtmpfs 176420 4 176416 0% /dev tmpfs 176420 0 176420 0% /dev/shm tmpfs 176420 272 176148 0% /run tmpfs 176420 0 176420 0% /sys/fs/cgroup tmpfs 176420 4 176416 0% /tmp tmpfs 176420 0 176420 0% /media/ram tmpfs 176420 0 176420 0% /var/volatile /dev/mmcblk0p2 1934248 37284 1798708 2% /media/mmcblk0p2