View source for EMMC OPOS8MM

[[Category: eMMC]]

= OPOS8MM eMMC layout =

By default, the 4GB eMMC on [[OPOS8MM]] module has 4 physical/hardware partitions:

{| border="1" cellpadding="10" cellspacing="0" summary="OPOS8MM eMMC partitions"
|----------------
| style="width:80px;background:orange;" align="center" | Boot0
| style="width:80px;background:orange;" align="center" | Boot1
| style="background:red;" | RPMB
| style="width:500px;background:green;color:white;" align="center" | User Data
|}


{| border="1" cellpadding="5" cellspacing="0" summary="OPOS8MM eMMC partitions details"
|- style="background:#efefef;" align="center"
!Name || U-Boot name || Size || Comment
|----------------
|boot0 || mmc dev 0 1 || 2MBytes || U-Boot is installed on this partition
|----------------
|boot1 || mmc dev 0 2 || 2MBytes || U-Boot env is installed on this partition
|----------------
|rpmb || mmc dev 0 3 || 512KBytes || Not used
|----------------
|User Data || mmc dev 0 0 || remaining space (~3,7GBytes) || Kernel, device tree and rootfs
|----------------
|}

== Boot0 partition layout ==
{| border="1" cellpadding="10" cellspacing="0" summary="OPOS8MM eMMC partitions"
|----------------
| style="width:10px;background:white;color:black;" align="center" | ...
| style="width:40px;background:orange;color:white;" align="center" | SPL
| style="width:100px;background:white;color:black;" align="center" | ...
| style="width:150px;background:orange;color:white;" align="center" | IMG
| style="width:150px;background:white;color:black;" align="center" | ...
|}

* Linux device: ''/dev/mmcblk0boot0''
{| border="1" cellpadding="5" cellspacing="0" summary="Boot0 partition detail"
|- style="background:#efefef;" align="center"
! Offset (blocks) || Offset (bytes) || Size (bytes) || Comment
|----------------
||| || || Free
|----------------
|0x42 || 33 KiB (0x8400) || 215 KiB || U-Boot SPL (opos8mm-u-boot.spl)
|----------------
||| || || Free
|----------------
|0x300 || 384 KiB (0x6000) || ~700 KiB || U-Boot IMG (opos8mm-u-boot.itb)
|----------------
||| || || Free
|----------------
|}

== Boot1 partition layout ==
{| border="1" cellpadding="10" cellspacing="0" summary="OPOS8MM eMMC partitions"
|----------------
| style="width:50px;background:orange;color:white;" align="center" | U-Boot env
| style="width:100px;background:white;color:black;" align="center" | ...
| style="width:50px;background:orange;color:white;" align="center" | U-Boot redundant env
| style="width:100px;background:white;color:black;" align="center" | ...
|}

* Linux device: ''/dev/mmcblk0boot1''
{| border="1" cellpadding="5" cellspacing="0" summary="Boot1 partition detail"
|- style="background:#efefef;" align="center"
! Offset (blocks) || Offset (bytes) || Size (bytes) || Comment
|----------------
|0 || 0 || 16 KiB || U-Boot environment
|----------------
||| || || Free
|----------------
|||  || 16 KiB || U-Boot redundant environment
|----------------
||| || || Free
|----------------
|}

== RPMB partition layout ==
* Not used !

== User Data partition layout ==

There are 3 partitions on the "User Data" physical partition:
{| border="1" cellpadding="10" cellspacing="0" summary="OPOS8MM eMMC partitions"
|----------------
| style="width:50px;background:white;color:black;" align="center" | ...
| style="width:100px;background:green;color:white;" align="center" | Failsafe/Update (primary)
| style="width:600px;background:green;color:white;" align="center" | Default Rootfs (primary)
| style="width:600px;background:green;color:white;" align="center" | Home/Data (primary)
|}


{| border="1" cellpadding="5" cellspacing="0" summary="OPOS8MM eMMC User data partitions details"
|- style="background:#efefef;" align="center"
!Name || U-Boot device  || Linux device || Offset (bytes) || Offset (sectors/blocs) || Size || Comment
|----------------
|MBR || NA || NA || 0 || 0 || 512 bytes (1 block) || Master Boot Record + some spare space ( -> Don't touch it :-) )
|----------------
|Failsafe || mmc 0:1 || /dev/mmcblk0p1 || 1M || 2048 (0x800) || 512 MBytes (1048576 sectors) || system/rootfs to restore your board in case of problem or setup a safe update mechanism (ext4 formatted)
|----------------
|Rootfs || mmc 0:2 || /dev/mmcblk0p2 ||  || 1050624 (0x10800) || 512 MBytes (1048576 sectors) || the default booted rootfs is on this partition (ext4 formatted)
|----------------
|Home/Data || mmc 0:3 || /dev/mmcblk0p3 ||  || 2099200 (0x200800) || Rest of space: ~2,7 GBytes (5634048 sectors) || HOME can be stored on this partition (ext4 formatted)
|----------------
|}

* By default, when flashed from U-Boot, rootfs and boot are only occupying the size of the .ext4 images used during flashing. If you want to increase the rootfs/boot size to all available free space then, after Linux has booted, use the following commands:
<pre class="apf">
# resize2fs /dev/mmcblk0p2        # for Rootfs
</pre>

* Or with ''apf-config'' command:
<pre class="apf">
# apf-config
</pre>
* In menu:
<pre class="config">
|     1 Expand Filesystem(s)         OS can then use all eMMC/SD space         |
</pre>

Rootfs/Boot will then be extended to all the "Rootfs"/"Boot" eMMC partitions space.

==Tips==
* Commands to partition ''User Data'' from fdisk on Host PC with [[U-Boot UMS on APF & OPOS|U-Boot UMS]]. '''Check /dev/sdc is your OPOS8MM device otherwise you may destroy your PC partition table !!!''':
<pre class=host>
$ sudo echo -e 'size=512MiB,type=0x83\nsize=512MiB,type=0x83\ntype=0x83' | sfdisk /dev/sdc

$ sudo mkfs.ext4 -O ^64bit,^metadata_csum,uninit_bg /dev/sdc1
$ sudo mkfs.ext4 -O ^64bit,^metadata_csum,uninit_bg /dev/sdc2
$ sudo mkfs.ext4 -O ^64bit,^metadata_csum,uninit_bg /dev/sdc3

</pre>

==Links==
* [http://fr.slideshare.net/linaroorg/intro-to-emmc http://fr.slideshare.net/linaroorg/intro-to-emmc]
* https://fr.wikipedia.org/wiki/Master_boot_record ou http://poloastucien.free.fr/mbr_fat_secteurs_boot_h.html