====== VIM1S Erase eMMC bootloader ======

We have several different ways to erase bootloader.
=====U-Boot console======


  - Connect your PC to the SBC using a [[products:sbc:vim1s:development:setup-serial-tool|Serial Debug Tool]].
  - As the SBC is booting-up, press ''SPACE''on the keyboard to enter the U-Boot mode.
  - Type ''store boot_erase bootloader'' into the U-Boot console, and wait for the erasure process to complete.
  - After erasure is completed, type ''reboot'' or press the ''RESET'' button on your SBC.

Use the following serial Terminal print-out as a reference:

```shell
kvim1s# store boot_erase bootloader
GUID Partition Table Header signature is wrong: 0x0 != 0x5452415020494645
GUID Partition Table Header signature is wrong: 0x0 != 0x5452415020494645
gpt is invalid


Caution! Your devices Erase group is 0x400
The erase range would be change to 0x0~0x23ff

8191 blocks erased: OK


Caution! Your devices Erase group is 0x400
The erase range would be change to 0x0~0x23ff

8191 blocks erased: OK


Caution! Your devices Erase group is 0x400
The erase range would be change to 0x0~0x23ff

8191 blocks erased: OK
kvim1s# reboot
```

If the eMMC has been erased, the serial Terminal should show this print-out when your SBC powers-on:

```txt
S4:BL:25dcde;ID:00D9C31D04901F08;FEAT:30F:1FFF0000:B002F:1;POC:DD;RCY:0;OVD:0;DFU:0;USB:ADFU�S4:BL:25dcde;ID:00D9C31D04901F08;FEAT:30F:1FFF0000:B002F:1;POC:DD;RCY:0;OVD:0;DFU:1;USB:0;RD-00:0;
```

===== Interrupt Mode =====

This erasure method is suitable for all products that use the Amlogic SoC:

  - Carry out eMMC flashing via a [[products:sbc:vim1s:install-os:install-os-into-emmc-via-usb-tool|USB-C cable]].
  - Manually interrupt the upgrading process (forcefully disconnect after 15% is recommended). For example, unplug the USB-C cable or eject the TF card.
  - Power on your SBC again, and you'll find that all the data on the eMMC has been erased.

===== Linux command-line =====

eMMC boot-loader can be stored on ''/dev/mmcblk0'' and special areas ''/dev/mmcblk0boot0'' or ''/dev/mmcblk0boot0''.

==== Cleanup eMMC boot loaders ====

Cleanup special eMMC boot areas. 

```sh
dd if=/dev/zero count=8192 | sudo tee /dev/mmcblk?boot? >/dev/null
```

Also need cleanup eMMC common boot area. 

```sh
sudo dd if=/dev/zero count=2000 seek=1 of=/dev/mmcblk0
```

<WRAP important >
''/dev/mmcblk0'' maybe different, please check how-to [[#get-block-device-names-for-boot-loaders]]
</WRAP>

==== Universal method for cleanup all eMMC boot-areas ====

```sh
sudo dd if=/dev/zero count=8192 | sudo tee /dev/mmcblk?boot? >/dev/null
sudo dd if=/dev/zero count=2000 seek=1 of=$(ls /dev/mmcblk?boot?|grep -m1 -o /dev/mmcblk.)

```

==== Get block-device names for boot loaders ====

Get block-device names for special boot areas.

```shell
~$ ls -1 /dev/mmcblk?boot? /dev/bootloader?
/dev/bootloader0
/dev/bootloader1
/dev/mmcblk0boot0
/dev/mmcblk0boot1
```
<WRAP important >
''/dev/bootloader?'' same areas as ''/dev/mmcblk?boot?'', but shifted by 512 bytes
</WRAP>

Get eMMC block-device name.

```shell
~$ ls -1 $(ls /dev/mmcblk?boot?|grep -m1 -o /dev/mmcblk.)
/dev/mmcblk0
```

==== How-to check boot loaders content ====

This example display empty content for special boot-loaders areas.

```shell
~$ for m in /dev/bootloader?;do echo $m; dd if=$m count=1 2>/dev/null | hexdump -C ;done 

/dev/bootloader0
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000200
/dev/bootloader1
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000200

```

Display same but for other boot areas names.

```shell
~$ for m in /dev/mmcblk?boot?;do echo $m; dd if=$m skip=1 count=1 2>/dev/null | hexdump -C ;done 

/dev/mmcblk2boot0
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000200
/dev/mmcblk2boot1
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000200
```

Next example display valid boot loader header ''@ML''.

```shell
~$ dd if=/dev/mmcblk0 count=1 skip=1 2>/dev/null | hexdump -C | head -n1
00000000  40 4d 4c 20 8d 66 31 ed  00 00 00 00 80 05 00 00  |@ML .f1.........|
```

/*
This erasure method is suitable for the SBC with Linux installed:

  - Power on and boot up.
  - Open a Terminal, and run ''dd'' to fill your bootloader partition with zeros:


```shell
khadas@Khadas:~$ sudo dd if=/dev/zero of=/dev/bootloader
dd: writing to '/dev/bootloader': No space left on device
8193+0 records in
8192+0 records out
4194304 bytes (4.2 MB, 4.0 MiB) copied, 1.1226 s, 3.7 MB/s
root@Khadas:~# reboot
```
*/