install problems

[mikebw at colossus.bilow.com (Mike Bilow)]

On 2000-05-30 at 09:49 -0400, Ron Peterson wrote:

> Mike Bilow wrote:
> > 
> > There is no need for /boot to be a separate partition.  Unless you have a
> > special situation, /boot is usually an ordinary directory below the
> > partition mounted as the root filesystem (/).
> 
> I've only used Red Hat.  Their installation manual recommends that /boot
> have its own partition, 16MB max.  They say this is a good idea "Due to
> the limitation of most PC BIOSes", but they don't elaborate further. 
> What are they talking about?

Any operating system must be loaded initially by the ROM BIOS, and the ROM
BIOS code used to access the hard drive is usually limited in some way.  
Older BIOSes could not access beyond the first 1024 cylinders of a hard
drive, which works out to 512 MB for the old-style IDE drives.  Nearly all
BIOSes in Pentium-class or better machines, however, have support for
24-bit Logical Block Addressing (LBA), which allows accessing the first
8.4 GB of the hard drive.  Most reasonably recent BIOSes within the last
few years have support for 32-bit LBA, which allows accessing up to 2 TB
(2048 GB), and that is large enough to hold us for a while.

If you are dealing with a very old machine, such as a 386 or 486, then you
might need to worry about this.  Also, some very old hard drives do not
have LBA support, but pretty much all hard drives large enough to be used
for Linux do have LBA support.  There are also a few special cases, as
with unusual SCSI controllers, where you will be limited to accessing the
first 1024 cylinders.  Other than these few situations, you are not
usually limited in this way.

You can also get into complications if you make your machine dual-boot
different operating systems.  However, any operating system with FAT32
support (Windows 95 B or later, Windows 98) supports LBA boot.

To enable 24-bit LBA support in Lilo, which allows bypassing the 1024
cylinder limit and booting from up to 8.4 GB partitions, use the
"linear" keyword in lilo.conf.  To enable 32-bit LBA support in Lilo,
which allows booting from up to 2 TB partitions, use the "lba32" keyword
in lilo.conf.  Note that the "lba32" support was released for Lilo only
about a month or two ago if you need this.

-- Mike


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