I'm trying to understand the partition table of my MTK-6572 based android smartphone (Karbonn-A35). The idea is to enlarge the internal Storage partition (mounted as
/data) and correspondingly shrink the Phone Storage partition (mounted as
/mnt/sdcard), so that I can install more apps on the phone without getting the "Disk Full" error. However, there is one thing I want to understand before proceeding to change the EBR1 partition file. Presently, here is how my MBR & EBR1 look like (yeah, I'm also wondering why the heck do they create an extended partition of 2TiB in size, whilst my sdcard is just 2GB!):
$disktype MBR --- MBR Regular file, size 512 bytes DOS/MBR partition map Partition 1: 2.000 TiB (2199023255040 bytes, 4294967295 sectors from 1024) Type 0x05 (Extended) Partition 2: 10 MiB (10485760 bytes, 20480 sectors from 18432) Type 0x83 (Linux) Partition 3: 10 MiB (10485760 bytes, 20480 sectors from 38912) Type 0x83 (Linux) Partition 4: 650 MiB (681574400 bytes, 1331200 sectors from 113152) Type 0x83 (Linux) $disktype EBR1 --- EBR1 Regular file, size 512 bytes DOS/MBR partition map Partition 1: 376 MiB (394264576 bytes, 770048 sectors from 1443328) Type 0x83 (Linux) Partition 2: 1.293 GiB (1388314624 bytes, 2711552 sectors from 2213376) Type 0x83 (Linux) Partition 3: 1.998 TiB (2196501691904 bytes, 4290042367 sectors from 4924928) Type 0x83 (Linux)
If you see the 4th and 5th partitions (i.e. the end of 4th in MBR and beginning of 1st in EBR1), there is some overlap. The fourth partition says
1331200 sectors from 113152. But when you count 1331200 sectors from 113152, you get 1444352 from where the next partition should begin. However, the next partition (i.e. the 1st in EBR) begins from 1443328 which is a bit earlier than that. Isn't that a kind of overlap for those few sectors (1444352−1443328=1024)? Those 1024 sectors are both part of 4th and 5th partitions? Or am I missing something about my understanding about partition tables?
That's one thing, another thing is about the third partition in EBR1. This wikipedia article on EBR says that only the first two entries in an EBR are supposed to be used:
EBRs have essentially the same structure as the MBR; except only the first two entries of the partition table are supposed to be used, besides having the mandatory boot record signature (or magic number) of 0xAA55 at the end of the sector.
Then how come the EBR1 of my device contains three entries? Again, is this a non-standard thing or am I missing something?
Hex output of the EBR1 showing the three entries: