[syslinux] Debugging memdisk loaded via pxelinux

Michael T. Davis DAVISM at ecr6.ohio-state.edu
Tue Oct 25 16:26:46 PDT 2011

At 08:42:24.02 on 25-OCT-2011 in message
<F0E5F8699DE1364584CDB894E9971355283A1E43 at YRDSB5.YRDSB.YRDSB.NET>, you wrote:

>Good day, Michael T. Davis.
>In regards to your query for how to query disk geometry, I'd suggest
>installing Syslinux to the USB flash drive's working partition and
>running Syslinux' DISK.C32 module from the 'boot:' prompt.  You will get
>the values for heads and cylinders, then you'll know what to pass to
>MEMDISK for the same size of image.
>  boot: disk.c32
>  DISK 0x80:
>    C/H/S: 16 heads, 1 cylinders
>           63 sectors/track, 1 drives
>    EDD:   ebios=1, EDD version: 30
>           16 heads, 2 cylinders
>           0 sectors, 512 bytes/sector, 63 sectors/track
>           Host bus: ISA, Interface type: ATA
>  LABEL usb_image
>    KERNEL memdisk
>    APPEND h=16 c=2
>    INITRD usb_image.hdd
>Also, please be sure that you are capturing the entire USB flash device,
>and not just the partition, when creating your image.

	OK, I get this:

DISK 0x80:
  C/H/S: 16 heads, 984 cylinders
         32 sectors/track, 1 drives
  EDD:   ebios=1, EDD version: 21
         16 heads, 984 cylinders
         503808 sectors, 512 bytes/sector, 32 sectors/track
         Host bus: , interface type:


  LABEL usb
  KERNEL memdisk
  APPEND harddisk h=16 c=984
  INITRD usb.imz


[...PXE load...]
Ramdisk at...
Moving compressed data...
gzip image: ...: ok
command line: harddisk h=16 c=984 initrd=usb.imz boot_image=memdisk
Disk is hd0, 251904 K, C/H/S = 984/16/32 (cmd/guess), EDD on, rw
[...other data not reporting any problems...]
Loading boot sector... booting...

Disk I/O error
Replace the disk, and then press any key

I am indeed dealing with an image of the entire disk, not just the partition.

There's still the open question I posed in that if the information that's
displayed as the PXE process runs on the client/target is useful for
presentation here, is there a mechanism for collecting it, aside from me
manually re-keying the information by hand?

>- Shao Miller


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