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- $Id: README.usbkey,v 1.2 2004/12/30 23:31:14 hpa Exp $
-
- The proper mode to boot a USB key drive in is "USB-HDD". That is the
- ONLY mode in which the C/H/S geometry encoded on the disk itself
- doesn't have to match what the BIOS thinks it is. Since geometry on
- USB drives is completely arbitrary, and can vary from BIOS to BIOS,
- this is the only mode which will work in general.
-
- Some BIOSes have been reported (in particular, certain versions of the
- Award BIOS) that cannot boot USB keys in "USB-HDD" mode. This is a
- very serious BIOS bug, but it is unfortunately rather typical of the
- kind of quality we're seeing out of major BIOS vendors these days. On
- these BIOSes, you're generally stuck booting them in USB-ZIP mode.
-
- THIS MEANS THE FILESYSTEM IMAGE ON THE DISK HAS TO HAVE A CORRECT
- ZIPDRIVE-COMPATIBLE GEOMETRY.
-
- A standard zipdrive (both the 100 MB and the 250 MB varieties) have a
- "geometry" of 64 heads, 32 sectors, and are partitioned devices with a
- single partition 4 (unlike most other media of this type which uses
- partition 1.) The 100 MB variety has 96 cylinders, and the 250 MB
- variety has 239 cylinders; but any number of cylinders will do as
- appropriate for the size device you have. For example, if your device
- reports when inserted into a Linux system:
-
- usb-storage: device found at 4
- Vendor: 32MB Model: HardDrive Rev: 1.88
- Type: Direct-Access ANSI SCSI revision: 02
- SCSI device sda: 64000 512-byte hdwr sectors (33 MB)
-
- ... you would have 64000/(64*32) = 31.25 cylinders; round down to 31.
-
- The script "mkdiskimage" which is supplied with the syslinux
- distribution can be used to initialize USB keys in a Zip-like fashion.
- To do that, calculate the correct number of cylinders (31 in the
- example above), and, if your USB key is /dev/sda (CHECK THE KERNEL
- MESSAGES CAREFULLY - IF YOU ENTER THE WRONG DISK DRIVE IT CANNOT BE
- RECOVERED), run:
-
- mkdiskimage -4 /dev/sda 0 64 32
-
- (The 0 means automatically determine the size of the device, and -4
- means mimic a zipdisk by using partition 4.)
-
- Then you should be able to run
-
- syslinux /dev/sda4
-
- ... and mount /dev/sda4 and put your files on it as needed.
-