[Android Q&A, Help & Troubleshooting] McBane87:
Hi Guys,

I've an Amlogic MX based Tablet and played a little around with some Kernel and ROMs and now I have the problem that my Data-Partition (/dev/block/data) is gone.

rootfs / rootfs rw 0 0
tmpfs /dev tmpfs rw,nosuid,relatime,size=410328k,nr_inodes=74092,mode=755 0 0
devpts /dev/pts devpts rw,relatime,mode=600,ptmxmode=000 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,relatime 0 0
debugfs /sys/kernel/debug debugfs rw,relatime 0 0
none /proc/bus/usb usbfs rw,relatime 0 0
none /acct cgroup rw,relatime,cpuacct 0 0
tmpfs /mnt/secure tmpfs rw,relatime,size=410328k,nr_inodes=74092,mode=700 0 0
tmpfs /mnt/asec tmpfs rw,relatime,size=410328k,nr_inodes=74092,mode=755,gid=1000 0 0
tmpfs /mnt/obb tmpfs rw,relatime,size=410328k,nr_inodes=74092,mode=755,gid=1000 0 0
none /dev/cpuctl cgroup rw,relatime,cpu 0 0
tmpfs /storage/external_storage tmpfs rw,relatime,size=410328k,nr_inodes=74092,mode=775,gid=1000 0 0
/dev/block/system /system ext4 ro,relatime,user_xattr,acl,barrier=1,data=ordered,noauto_da_alloc 0 0
/dev/block/cache /cache ext4 rw,nosuid,nodev,noatime,nodiratime,user_xattr,acl,barrier=1,data=ordered,noauto_da_alloc 0 0
/dev/block/mtdblock6 /factory yaffs2 rw,nosuid,nodev,relatime 0 0
/dev/fuse /mnt/shell/emulated fuse rw,nosuid,nodev,relatime,user_id=1023,group_id=1023,default_permissions,allow_other 0 0
/dev/block/vold/253:1 /storage/external_storage/sdcard1 vfat rw,dirsync,nosuid,nodev,noexec,relatime,gid=1015,fmask=0002,dmask=0002,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro 0 0

ls -l /dev/block/
brw------- root root 250, 28 2014-07-26 11:21 cache
brw------- root root 253, 0 2014-07-26 11:21 cardblksd
brw------- root root 253, 1 2014-07-26 11:21 cardblksd1
brw------- root root 250, 24 2014-07-26 11:21 factory
brw------- root root 7, 0 2014-07-26 11:21 loop0
brw------- root root 7, 1 2014-07-26 11:21 loop1
brw------- root root 7, 2 2014-07-26 11:21 loop2
brw------- root root 7, 3 2014-07-26 11:21 loop3
brw------- root root 7, 4 2014-07-26 11:21 loop4
brw------- root root 7, 5 2014-07-26 11:21 loop5
brw------- root root 7, 6 2014-07-26 11:21 loop6
brw------- root root 7, 7 2014-07-26 11:21 loop7
brw------- root root 31, 0 2014-07-26 11:21 mtdblock0
brw------- root root 31, 1 2014-07-26 11:21 mtdblock1
brw------- root root 31, 2 2014-07-26 11:21 mtdblock2
brw------- root root 31, 3 2014-07-26 11:21 mtdblock3
brw------- root root 31, 4 2014-07-26 11:21 mtdblock4
brw------- root root 31, 5 2014-07-26 11:21 mtdblock5
brw------- root root 31, 6 2014-07-26 11:21 mtdblock6
brw------- root root 31, 7 2014-07-26 11:21 mtdblock7
brw------- root root 31, 8 2014-07-26 11:21 mtdblock8
drwxr-xr-x root root 2014-07-26 11:21 platform
brw------- root root 1, 0 2014-07-26 11:21 ram0
brw------- root root 1, 1 2014-07-26 11:21 ram1
brw------- root root 1, 10 2014-07-26 11:21 ram10
brw------- root root 1, 11 2014-07-26 11:21 ram11
brw------- root root 1, 12 2014-07-26 11:21 ram12
brw------- root root 1, 13 2014-07-26 11:21 ram13
brw------- root root 1, 14 2014-07-26 11:21 ram14
brw------- root root 1, 15 2014-07-26 11:21 ram15
brw------- root root 1, 2 2014-07-26 11:21 ram2
brw------- root root 1, 3 2014-07-26 11:21 ram3
brw------- root root 1, 4 2014-07-26 11:21 ram4
brw------- root root 1, 5 2014-07-26 11:21 ram5
brw------- root root 1, 6 2014-07-26 11:21 ram6
brw------- root root 1, 7 2014-07-26 11:21 ram7
brw------- root root 1, 8 2014-07-26 11:21 ram8
brw------- root root 1, 9 2014-07-26 11:21 ram9
brw------- root root 250, 20 2014-07-26 11:21 system
drwx------ root root 2014-07-26 11:21 vold

If I flash an older Stock-ROM with UBIFS the Data-Partition is there, but not as Ext4-Partition.

ubi0_0 /system ubifs rw,relatime 0 0
ubi1_0 /data ubifs rw,nosuid,nodev,relatime 0 0
/dev/block/mtdblock7 /cache yaffs2 rw,nosuid,nodev,relatime 0 0

After flashing back to a newer Stock-Rom with Android 4.2.2 (EXT4-ROM), I have the same issue as above,

Recovery stops with following output:

Finding update package...
Openning update package...
Verifying update package...
Installing update...
Formatting /cache...
Formatting /data...
Formatting /cache...
Data wipe failed.
Formatting /cache...
Cache wipe failed.

CWM is a little more verbose with this:

E:format_volume: make_extf4fs failed on /dev/block/data

Anyone a Idea how to recover Ext4-Data-Partition?

Thanks.