lilo is nearly worst of breed in terms of putting magic stuff in the Master Boot Record.
[email protected] wrote: > On Tue, 28 Jul 2009, Mitch Bradley wrote: > >> [email protected] wrote: >>> On Tue, 28 Jul 2009, Mitch Bradley wrote: >>> >>>> Another important advantage to partitions is that the existence of >>>> a boot partition isolates the firmware from changes in the >>>> filesystem used for the root. >>> >>> can you explain this a bit more? >> >> A conventional BIOS boots by reading a small chunk of 16-bit >> real-mode code from the Master Boot Record, which then does something >> magic, often involving chaining to some other chunk of code that is >> shoehorned into some location that is difficult to inspect (e.g. some >> reserved sectors near the beginning of a partition). > > I'll point out that lilo allows it to boot from stuff anywhere in the > filesystem, and does not have to understand the specific filesystem at > boot time. > > there are cases where it doesn't work well, but in the limited case of > the XO laptops I think it would work well (and avoid the complexity > you describe below) > > Davi dLang > >> OFW instead reads the kernel and initrd files directly from the >> filesystem - there are no hidden chunks of 16-bit code tucked into >> nooks and crannies. >> >> Linux filesystems tend to evolve rapidly. ext2/3 sprouted numerous >> extensions over the years, some of them backwards compatible and some >> not. Now we have ext4, which an ext2 reader can't necessarily >> handle. At some point we might want to switch to btrfs, which would >> require yet another reader. OFW will probably eventually acquire a >> btrfs reader just for diagnostic purposes, but from a stability and >> ease of migration standpoint, it's better to pin down the format of >> the boot partition, thus decoupling the evolution of the OS from the >> firmware. >> >> UEFI has taken the same approach - a boot partition with a FAT >> filesystem. >> >> The boot partition is useful not only for the kernel, but also for >> firmware extensions like extra diagnostics, alternate startup >> graphics, alternate fonts, localizations, ... >> > _______________________________________________ Devel mailing list [email protected] http://lists.laptop.org/listinfo/devel
