[gentoo-user] cannot open root device "sda3"

[Valmor de Almeida]

Hello,

I am trying to boot gentoo from an external USB HDD.  I am getting the
error message:

  VFS: Cannot open root device "sda3" or unknown-block(2,0)
  Please append a correct "root=" boot option; here are the available
partitions:
  Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)

I am assuming that the device will be named /dev/sda since there is no
other HDD on the system. The message above does not list any available
partitions.
Any thoughts?

Here is the info from fdisk on this drive (it is a new 4096-byte sector drive):

  Disk /dev/sdb: 240.1 GB, 240057409536
  255 heads, 63 sectors/track, 29185 cylinders
  Units = cylinders of 16065 * 512 = 8225280 bytes
  Disk identifier: 0x0c7786a9

  Device       Boot     Start     End        Blocks       Id  System
  /dev/sdb1     *              1       26        208813+    83  Linux
  /dev/sdb2                   27     158      1060290      82  Linux
swap / Solaris
  /dev/sdb3                 159    2117    15735667+    83  Linux
  /dev/sdb4                2118  29185  217423710      8e Linux LVM

Thanks,

--
Valmor