[HD2 Android NAND Development] bauner:
1. you could install an terminal emulator from market and type mount inside

in the output you find an line which contains /data

example:

/dev/block/mmcblk0p2 /data ext4 rw,nosuid,nodev,noatime,nodiratime,errors=remount-ro,barrier=1,journal_async_commit,data=writeback,noauto_da_alloc 0 0

With active ext4 partition the beginning of the line is

/dev/block/mmcblk0p2 /data ext4

With active ext2 partition the beginning of the line is

/dev/block/mmcblk0p2 /data ext2

With active data.img the beginning of the line is

/dev/block/loop9 /data ext2

With active internal data partition the beginning of the line is

/dev/block/mtdblock? /data yaffs2

2. Thats depending on your config.txt settings

3. the mount_data_img_sync= is only active if you use data.img (use_dataimg=1)

4. You need to already have 2 partitions before you can use it as your data partition

The first partition must be an an valid fat32 partition!

The second partition (max 2048mb) needs only to exist (can be raw or formatted with any filesystem)

here some setting examples

If you want to use an ext4 partition for userdata (my recommendation) (make sure that an 2nd partition already exist)

use_ext4_partition=1

format_ext4_partition=1 (to format it with ext4 on 1. boot! after format this is automaticly set to 0 to prevent from running again..)

use_ext2_instead_ext4=0

use_reiserfs_instead_ext4=0

use_btrfs_instead_ext4=0

use_dataimg=0

data_img_size=256 (ignored if use_ext4_partition=1)

mount_data_img_sync=1 (ignored if use_ext4_partition=1)

copy_data_from_nand=0 (explained under backup settings)

copy_data_from_img_to_ext4=0 (explained under backup settings)

backup_current_data=0 (explained under backup settings)

backupfile_free_space=50 (explained under backup settings)

wipe_dalvik_cache=0

run_fix_permissions=0

recover_data_from_backup=0 (explained under backup settings)

If you want to use an data.img file on your fat32 partition for userdata (no need of an second partition)

use_ext4_partition=0

format_ext4_partition=0

use_ext2_instead_ext4=0

use_reiserfs_instead_ext4=0

use_btrfs_instead_ext4=0

use_dataimg=1

data_img_size=256 (if no data.img is in /sdcard/data/ a new one with the size you set (in this case 256) gets created on boot)

mount_data_img_sync=1 (1= your data.img is mounted sync to prevent data corruption but is slower; 0= mount async is faster but the risk of data loss is higer)

copy_data_from_nand=0 (explained under backup settings)

copy_data_from_img_to_ext4=0 (ignored if use_dataimg=1)

backup_current_data=0 (explained under backup settings)

backupfile_free_space=50 (explained under backup settings)

wipe_dalvik_cache=0

run_fix_permissions=0

recover_data_from_backup=0 (explained under backup settings)

To use the phones internal data partition:

use_ext4_partition=0

format_ext4_partition=0

use_ext2_instead_ext4=0

use_reiserfs_instead_ext4=0

use_btrfs_instead_ext4=0

use_dataimg=0

Backup settings

If you already have data on your internal data partiton you can autocopy it into ext4 partition or data.img on next reboot with this:

copy_data_from_nand=1

(after copy it switches back to 0 to prevent from running again on reboot)

To make an backup from the actual in config.txt enabled data partition (internal, ext4 partition or data.img) to /sdcard/backup.img on next reboot:

copy_data_from_nand=0

copy_data_from_img_to_ext4=0

backup_current_data=1

backupfile_free_space=50 ((The free space in mb inside backup.img) if you want to use the backup.img direct as data.img if you rename it)

recover_data_from_backup=0

(backup_current_data switches back to 0 to prevent from running again on reboot)

To restore your files from backup.img to ext4 partition (if use_ext4_partition=1) or data.img (if use_dataimg=1) because of the low space restoring to the phones internal partition is not possible:

copy_data_from_nand=0

copy_data_from_img_to_ext4=0

backup_current_data=0

backupfile_free_space=50 (ignored here)

recover_data_from_backup=1

(recover_data_from_backup switches back to 0 to prevent from running again on reboot)