source: trunk/syslinux-doc/README.usbkey @ 106

Last change on this file since 106 was 106, checked in by bas, 14 years ago

Added pxemenu config files and updated some info

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1The proper mode to boot a USB key drive in is "USB-HDD".  That is the
2ONLY mode in which the C/H/S geometry encoded on the disk itself
3doesn't have to match what the BIOS thinks it is.  Since geometry on
4USB drives is completely arbitrary, and can vary from BIOS to BIOS,
5this is the only mode which will work in general.
6
7Some BIOSes have been reported (in particular, certain versions of the
8Award BIOS) that cannot boot USB keys in "USB-HDD" mode.  This is a
9very serious BIOS bug, but it is unfortunately rather typical of the
10kind of quality we're seeing out of major BIOS vendors these days.  On
11these BIOSes, you're generally stuck booting them in USB-ZIP mode.
12
13THIS MEANS THE FILESYSTEM IMAGE ON THE DISK HAS TO HAVE A CORRECT
14ZIPDRIVE-COMPATIBLE GEOMETRY.
15
16A standard zipdrive (both the 100 MB and the 250 MB varieties) have a
17"geometry" of 64 heads, 32 sectors, and are partitioned devices with a
18single partition 4 (unlike most other media of this type which uses
19partition 1.)  The 100 MB variety has 96 cylinders, and the 250 MB
20variety has 239 cylinders; but any number of cylinders will do as
21appropriate for the size device you have.  For example, if your device
22reports when inserted into a Linux system:
23
24usb-storage: device found at 4
25  Vendor: 32MB      Model: HardDrive         Rev: 1.88
26  Type:   Direct-Access                      ANSI SCSI revision: 02
27SCSI device sda: 64000 512-byte hdwr sectors (33 MB)
28
29... you would have 64000/(64*32) = 31.25 cylinders; round down to 31.
30
31The script "mkdiskimage" which is supplied with the syslinux
32distribution can be used to initialize USB keys in a Zip-like fashion.
33To do that, calculate the correct number of cylinders (31 in the
34example above), and, if your USB key is /dev/sda (CHECK THE KERNEL
35MESSAGES CAREFULLY - IF YOU ENTER THE WRONG DISK DRIVE IT CANNOT BE
36RECOVERED), run:
37
38        mkdiskimage -4 /dev/sda 0 64 32
39
40(The 0 means automatically determine the size of the device, and -4
41means mimic a zipdisk by using partition 4.)
42
43Then you should be able to run
44
45        syslinux /dev/sda4
46
47... and mount /dev/sda4 and put your files on it as needed.
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