From d8712ac3af454d2530eff47c3f7b0ff44a20bd0b Mon Sep 17 00:00:00 2001 From: hpa Date: Thu, 30 Dec 2004 21:15:22 +0000 Subject: [PATCH] Documentation about USB keys --- NEWS | 6 +++++- README.usbkey | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 51 insertions(+), 1 deletion(-) create mode 100644 README.usbkey diff --git a/NEWS b/NEWS index 48b4a68..ce3533b 100644 --- a/NEWS +++ b/NEWS @@ -36,7 +36,11 @@ Changes in 3.00: to write an MBR and -a to mark the partition SYSLINUX is being installed on active. * MEMDISK: Give a way to query the boot loader type while - running MEMDISK; see memdisk/memdisk.doc and sample/mdiskchk.c. + running MEMDISK; see memdisk/memdisk.doc and + sample/mdiskchk.c. + * mkdiskimage: substantially improved mkdiskimage which, among + other things, can now be used to initialize USB keys as + zipdrives; see README.usbkey for more information. Changes in 2.13: * MEMDISK: Fix command-line parsing "brown paper bag" class diff --git a/README.usbkey b/README.usbkey new file mode 100644 index 0000000..4154cce --- /dev/null +++ b/README.usbkey @@ -0,0 +1,46 @@ +$Id$ + +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 31 64 32 + +Then you should be able to run + + syslinux /dev/sda4 + +... and mount /dev/sda4 and put your files on it as needed. -- 2.7.4