Re: boot partition
- From: Jean-David Beyer <jeandavid8@xxxxxxxxxxx>
- Date: Fri, 16 Jan 2009 12:41:53 GMT
Allen Kistler wrote:
annalissa wrote:I have recently read that
Linux /boot partition should be 16-32 MB, and it must be within the
first 1023 cylinders or 8 GBytes of your hard drive. It does not
matter whether /boot is a primary or logical partition.
can any one explain to me why this so ?
16-32 MB is tiny. You must have read a really old book. 100 MB would be closer to reality for current kernels and initrds, unless you're using a kernel customized to be small.
I have Red Hat Enterprise Linux and I have a separate /boot partition. There is no longer any reason for that, but in the old days (mid 1990s) some machines required it to be in the first 1024 cylinders. I bought my first home machine, a white box with Windows 95 in it. When I wanted to put Linux on it, I bought a new hard drive and added it to the existing machine. In those days, drives were small: the original drive was about 1.5 GBytes and the new one was 4.3 GBytes. I do not know if the cylinders reported by the IDE drives (WD Caviar drives) were true cylinders or not.
8 or so years later, the 4.3 GByte drive quit (motor would not spin), so I got the smallest hard drive I could (80 GBytes), and it was too big. The BIOS would not recognize it and would not go any further in the boot process. So I told the BIOS that I had only 1 drive, the 1.5 GByte one. Linux could find the other without the BIOS.
Boot loaders use the BIOS disk functions to read in the /boot partition. Older BIOSes couldn't handle disks larger than 1023 cylinders. Modern BIOSes aren't so restrictive.
As to physical vs. logical, I personally haven't tried to make a whole disk nothing but logical partitions. Whether or not you can make /boot a logical partition depends on the boot loader.
Most people (and automated installers) still usually put /boot first on the disk as a physical partition because that makes the most sense. After the boot loader, it's the first thing to load.
That does not seem to be true of my other machine. On that machine, the first drive is EIDE. The first partition is NTFS with Windows XP in it. The second is FAT32 with more W.XP in it that I can read and write from linux. That is 3657 cylinders altogether. Only then did CentOS put the /boot partition (since the Windows stuff was already there), and it all works just fine.
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- From: annalissa
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- From: Allen Kistler
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