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Ask HN: Where can I find a primer on how computers boot?

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Ask HN: Where can I find a primer on how computers boot?

#1

Post by mog_dev »

As a developer, I recently encountered challenges with GRUB and discovered I lacked knowledge about my computer's boot process. I realized terms like EFI partition, MBR, GRUB, and Bootloader were unfamiliar to me and many of my colleagues. I'm seeking introductory and easy-to-understand resources to learn about these concepts. Any recommendations would be appreciated!

Re: Ask HN: Where can I find a primer on how computers boot?

#4

Post by anenefan »

I would say start at wikipedia looking up terms and consider a couple of weeks to grasp the simple notions of what's involved. Start with MBR, limits on old drives, dig into various tricks to get around limitations ... not really relevant present day but it's good insight.

Problems with bootlaoders are generally specific to the system it's on and how the drive(s) is / are set up.

https://www.linux.org/threads/linux-bootloaders.8943/

https://www.tecmint.com/best-linux-boot-loaders/

I think even old versions of Scott Mueller's "Upgrading and Repairing Pcs" might be of use to you. Digital versions could be found at archive.org.

Re: Ask HN: Where can I find a primer on how computers boot?

#9

Post by ignoramous »

The gist is (which doesn't hold universally true), when the CPU is powered up, it initializes its internal RAM, loads in a pre-boot ROM, executes it. pre-boot ROM's job is to initialize whatever it has to, to bring in the initial bootloader which initializes RAM, finds a suitable bootloader program and loads it in. This program, also called second-stage bootloader, is an Operating System in its own right. It can understand filesystems, explore attached hardware, speak multiple network protocols, initialize devices as needed. The second-stage bootloader (there may also be a third-stage) usually then boots into a Kernel. The Linux Kernel invokes the init process and things proceed into the userspace from there.

At each of those stages, the bootloader images, the kernel image, the device trees, and the disk / filesystem are verified ("measured") for integrity eventually anchored on a "hardware root-of-trust".

If you're a visual learner:

How TI Beagleboard boots (33m): https://www.youtube.com/watch?v=DV5S_ZSdK0s / https://ghostarchive.org/varchive/DV5S_ZSdK0s

How ARM Cortex M boots (9m): https://www.youtube.com/watch?v=3brOzLJmeek / https://ghostarchive.org/varchive/3brOzLJmeek

Bootloader 101 (embedded devices; 38m): https://www.youtube.com/watch?v=UvFG76qM6co / https://ghostarchive.org/varchive/UvFG76qM6co

Measured Boot (39m): https://www.youtube.com/watch?v=EzSkU3Oecuw / https://ghostarchive.org/varchive/EzSkU3Oecuw

Coreboot (38m): https://www.youtube.com/watch?v=iffTJ1vPCSo / https://ghostarchive.org/varchive/iffTJ1vPCSo

U-Boot (1h 25m): https://www.youtube.com/watch?v=INWghYZH3hI

UEFI for U-Boot (38m): https://www.youtube.com/watch?v=VnsF3uRZzNk / https://ghostarchive.org/varchive/VnsF3uRZzNk

Device Trees (43m): https://www.youtube.com/watch?v=Nz6aBffv-Ek / https://ghostarchive.org/varchive/Nz6aBffv-Ek

ARM Trust Zone (46m): https://www.youtube.com/watch?v=q32BEMMxmfw

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