Thread: Understanding boot sectors and MBR

hi,
attempting setup multiboot linux usb hard drive , little confused how setup bootloader. more learning experiment , trying avoid gui tools.
understanding mbr contained boot code in first 446 bytes , partition table , id after that.
in attempt have partitioned drive thus;
hda1 - 30mb ,primary bootloader files.
hda2 - 6gb logical ubuntu partition.
hda3 - 6gb logical backtrack partition
hda4 - fat32 storage partition.
have used logical partitions linux distros can have multiple installs once figure things out.

problem booting extended partition. automated tools have used create isolinux installs seem write boot code mbr , not first sector of partition.
have tried boot ubuntu install grub floppy 'boot error' following code

root (hd0,4)
chainloader +1
boot

installed grub4dos windows xp ntldr/boot.ini method , once booted grub4dos command works fine. why difference?
can install grub4dos mbr of usb drive if use tool make distro install overwrites , drive becomes unbootable.
can restore mbr bootable grub4dos tools still can't boot ubuntu, returns 'boot error' grub. if copy bootsector mbr bootsector of ubuntu partition messes partition table.
dd if=/dev/sdc of=/dev/sdc2 bs=446 count=1
how can make ubuntu partition bootable? , why copying bootsector effect partition table @ all??
cheers help.

sorry can't little more i'm dealing same type of issues. far have found these links seem outdated still educational. figure since doing educational thing in thread should compile best information. here's 2 links managing multiple operating system seem give thorough explanation how operating system installed. background information think.

http://ldp.linuxhelp.ca/howto/pdf/multios-howto.pdf
http://www.pcmag.com/article2/0,2817,1730836,00.asp
http://www.linuxselfhelp.com/howto/multios-howto-6.html

terminal code pull manual of code in terminal
example can mount command:~ man mount ( shows manual mount command)

if find others let me know should make new pdf document 1 that's updated , focuses , sata, speed , ever else you'd add.

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