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If you're lucky and your machine supports coreboot there is even better way to boot into linux - use slimmed down linux kernel as a direct payload of coreboot a

by kamyl 4y ago

If you're lucky and your machine supports coreboot there is even better way to boot into linux - use slimmed down linux kernel as a direct payload of coreboot and kexec into your actual kernel. This way you're skipping any disadvantages of grub (if you can name any which matter) and don't need to deal with relatively new and not as much battle tested code to boot your trusted kernel.

pabs3 4y ago
Does this mean you're installing Linux into write-limited flash? If so that could eventually brick your system.
- kamyl 4y ago
  No, just an intermediate kernel is written into flash memory along with coreboot. It doesn't wear little flash chip as it doesn't write anything which needs to persist, that's actually one of the points of this solution. Its sole role is to chain-load your destination kernel. So you just basically move your bootloader into non trivially writable memory (as it can be write-locked) to make it more tamper proof. There is always a risk of bricking your system if you're not careful, but wearing off flash isn't one of those risks if that's the concern.
- KirillPanov 4y ago
  Nope; bootloader flash chips use NOR instead of NAND flash precisely to prevent this. NOR flash guaranteed for a minimum of 100,000 complete rewrites of every cell, with no flash translation layer gimmickery. The downside is that it is very expensive, which is why a few dozen megabytes of NOR flash costs as much as many gigabytes of MLC NAND. Typical NOR flash chip; "Minimum 100,000 Program/Erase Cycles": https://www.gigadevice.com/flash-memory/gd25b127d/ NAND flash vendors often advertise "up to" a similar number of P/E cycles on their SLC devices, but you'll have a hard time getting them to guarantee that. And for TLC and MLC NAND you find in non-industrial products the number is more like 3% of that: https://www.kingston.com/en/blog/pc-performance/difference-between-slc-mlc-tlc-3d-nand TL;DR: bootloader flash chips are chosen such that they are nearly impossible to "wear out".

by kamyl 4y ago

pabs3 4y ago

Does this mean you're installing Linux into write-limited flash? If so that could eventually brick your system.

kamyl 4y ago
No, just an intermediate kernel is written into flash memory along with coreboot. It doesn't wear little flash chip as it doesn't write anything which needs to persist, that's actually one of the points of this solution. Its sole role is to chain-load your destination kernel. So you just basically move your bootloader into non trivially writable memory (as it can be write-locked) to make it more tamper proof. There is always a risk of bricking your system if you're not careful, but wearing off flash isn't one of those risks if that's the concern.
KirillPanov 4y ago
Nope; bootloader flash chips use NOR instead of NAND flash precisely to prevent this. NOR flash guaranteed for a minimum of 100,000 complete rewrites of every cell, with no flash translation layer gimmickery. The downside is that it is very expensive, which is why a few dozen megabytes of NOR flash costs as much as many gigabytes of MLC NAND. Typical NOR flash chip; "Minimum 100,000 Program/Erase Cycles": https://www.gigadevice.com/flash-memory/gd25b127d/ NAND flash vendors often advertise "up to" a similar number of P/E cycles on their SLC devices, but you'll have a hard time getting them to guarantee that. And for TLC and MLC NAND you find in non-industrial products the number is more like 3% of that: https://www.kingston.com/en/blog/pc-performance/difference-between-slc-mlc-tlc-3d-nand TL;DR: bootloader flash chips are chosen such that they are nearly impossible to "wear out".