Inside the Linux boot process

linux boot processJust an interesting tid-bit that I had been wondering about for a while: why is there a "boot stage 1.5" during Linux boot? I see a "stage 1" notification, then stage 1.5, but nothing else... How come?
Well, IBM has the answer in "Inside the Linux boot process". Linux uses a 2 stage boot process, stage 1 loads the boot loader, stage loads the kernel. But to allow Linux to load the kernel from a native file system such as ext2 or ext3 (or Reiser, XFS, ZFS, etc.), GRUB introduces an additional stage 1.5 that understands those file systems. Stage 2 then still loads the kernel, only now it can reside in a normal Linux partition instead of a raw disk sectors, such as with LILO. Neat!


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