How To: Prepare SD Card for boot
SD Card Memory Map
- Bootloader u-boot: a small program that put the operating system into the memory
- Kernel UImage: the lowest level of software that interfaces with the hardware in computer. It is responsible for interfacing all the applications in "user mode" to physical hardware. It also allow processes to get information from each other using inter-process communication (IPC).
- Rootfs //rootfs/folder : a special instance of a very simple filesystem that exports Linux's disk caching mechanisms as a dynamically resizable RAM-based filesystem.
Create a bootable SD card
Steps to create your HIO Yocto SD card image:
1. Acquire SD Card ID
Plug a mini SD card into the computer, then display the device ID of SD card using command:
Skip Step 2 if the SD card is empty and has no partition.
2. Optional: Delete Partition
Caution: Partitioning the drive will erase all of its data content permanently.
Acquire the card name, for this tutorial, we will use /dev/sdc.
$ sudo fdisk /dev/sdc p display note of the start sector d delete 1 first partition d delete 2 second partition p display w write
Unplug and plug-in the SD Card to reset.
3. Create Partition
We have to create 2 Partitions. One is for the u-boot and kernel and one is for rootfs.
$ sudo fdisk /dev/sdc p display note of the start sector n create partition p primary selection 1 first partition (for kernel) first sector +100M (for u-boot) last sector +200M n create partition p primary selection 2 second partition (for rootfs) first sector +400M last sector default (use all the remaining space) p display w write
Unplug and plug-in the SD Card.
4. Format Partition
The card needs to be formatted to write into. Enter the following command into terminal.
Caution: Formatting will erase all data of the card.
Assume that the card name is sdc and the 2 partitions are sdc1 and sdc2
$ sudo mkfs.vfat /dev/sdc1 $ sudo mkfs.ext4 /dev/sdc2