You'll probably have to use some other bootloader/method than this fastboot. Once loaded, an ordinary kernel boot can commence.ītw: I am asking the question because of an app I am developing I'd like to "risk free" boot a custom kernel directly from the device, where it is stored e.g. The optional rootfs (a ramdisk or maybe an initramfs image) can also be loaded from the host over USB into memory. The kernel in loaded from the host over USB into memory. The fastboot program is an alternate bootloader that executes after you reboot the device. The optional root filesystem of this operation is clearly specified as a ramdisk image, which would also not require writing to or storage in a partition.ĭoes anyone know how it internally works? If the sole intent is to boot the system using the kernel image, then there is simply no reason to also write the kernel image to a partition, especially when one has not been explicitly specified. the kernel image is loaded from a server/host over an Ethernet link using TFTP. This fastboot is similar to a netboot, e.g. reading into memory) the kernel image from a storage device. No, there would be no modification to any partition.īooting a kernel means loading (i.e. Is the kernel copied to a special boot partition before rebooting the device? img format and lets name it boot.img) Code: fastboot flash boot boot.img. I mean, how the flashing feature works is pretty easy, I can imitate it by just copying a boot image with a custom kernel to the boot partition, e.g., via:ĭd if='' of='/dev/block/platform/msm_sdcc.1/by-name/boot'ītw: I am asking the question because of an app I am developing I'd like to "risk free" boot a custom kernel directly from the device, where it is stored e.g. navigate to the folder it is in (should be in.
#FASTBOOT SOURCE CODE CODE#
It is very useful while developing a kernel or modifying the rootfs.ĭoes anyone know how it internally works? Is the kernel copied to a special boot partition before rebooting the device? ( UPDATE: As the answer points out, there is no reboot, as fastboot is a step in the boot process, which basically makes my question meaningless.) I was looking into the source code of fastboot, but it seems it contains only what happens on the host side, and not on the device.
#FASTBOOT SOURCE CODE DOWNLOAD#
This command allows you to download a kernel image (and optional root filesystem image) and boot the phone with those, instead of using the kernel and rootfs in the boot flash partition. Fastboot has the following handy feature (if booting the custom image fails, the device just magically boots the default image next time, and all's gonna be alright):
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