How to boot multiple kernels

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How to boot multiple kernels

Postby Sunate » Tue Jun 15, 2021 10:44 am

I have built different kernels and was able to install them and boot them on my RPi (B2/3 and Zero(B+)). What I want to do is have multiple kernels and be able to select which one I want to boot. Since RPi does not use grub, the way that is outlined for Arch will not work. Also, the instructions I have found are for 3.x kernels and do not use initramfs and also do not work. Can anyone guide me as to how to have multiple kernels (modules and dsds) and be able to boot each one? If there is a succinct wiki or howto, a pointer would be allreciated as I ahve googled quite a bit and cannot find anything. So far, the only way I have been able to do it is to keep the package and use "pacman -U xxx.xz --force" to install and boot one versus the other. If this is the only way, that is fine, but I'd like to know if there is a 'better way' (tm).
Last edited by Sunate on Thu Jun 17, 2021 6:17 am, edited 1 time in total.
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Re: How to boot multiple kernels

Postby moonman » Wed Jun 16, 2021 4:27 am

You can't with RPi bootloader as it looks for specific kernel filename in a specific location. If you chain boot U-Boot, then you can setup U-Boot environment that loads and boots a particular kernel for you by removing the default bootcmd, and running something like "run boot_kernel1" at the prompt during boot

What I do not know is
- Does U-Boot for rpi support screen output - if not you are SOL, or you may have to enable support for HDMI output if it's not enabled etc. Does it support USB keyboards. Same as with the HDMI output
- can you boot RPi non-mainline kernel with it - if not you are stuck with mainline

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