The hd bootstring overrides the default search
sequence used by the hd driver to determine
the root disk. The syntax of the bootstring is:
hd=driver
where driver is the disk driver prefix.
Valid driver prefixes are:
esdi
ESDI disk controller on MCA machines
ida0
Compaq IDA controller
st506
ST506 disk controller on MCA machines
Sdsk
generic SCSI disk driver for all machine architectures
wd0
generic Western Digital WD1010 disk driver for
controllers such as ESDI and IDE
that present a ST506 interface on ISA
and EISA machines
This bootstring is required by those controllers (such as
some Compaq IDA and some SCSI host adapters)
that appear to be WD1010-style controllers. By default,
hd recognizes the wd driver before
the Sdsk or ida drivers.
This prevents these disks from being configured as the
root disk.
To boot from a Compaq IDA drive,
you would use the bootstring hd=ida0.
You should add this bootstring to the definition of
DEFBOOTSTR in the file /etc/default/boot so
that the system uses the correct root disk configuration when it boots.