OpenWRT x86 Style Disks and Booting: Difference between revisions

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Copy the MBR (GRUB Stage 1 and Partition Table): <code>dd if=/dev/sdX of=/dev/sdY bs=512 count=1</code>

Copy the (GRUB Stage 1.5, containing the CORE.IMG file): <code>dd if=/dev/sdX of=/dev/sdY bs=512 skip=1 count=511</code>

Copy the "MBR Gap" (GRUB Stage 1.5, containing the CORE.IMG file): <code>dd if=/dev/sdX of=/dev/sdY bs=512 skip=1 count=511</code>

Copy the First Partition (/boot Directory): <code>dd if=/dev/sdX1 of=/dev/sdY1 bs=128M conv=noerror progress=status</code>

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Flush any buffered information to disk: <code>sync</code>

Notes;

Syntax Notes;

*if: Input File (or Device)

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*progress = status: Show the progress of the copy process (only for a certain version of DD and up)

*sync: Write all buffered blocks to disk (just to be safe)

Other Notes

*Copying the MBR and MBR Gap can be combined into a single step (it was done to clarify and make an explicit point that there is important code stored in the MBR Gap necessary to boot OpenWRT with GRUB): <code>dd if=/dev/sdX of=/dev/sdY bs=512 count=512</code>

*The "MBR Gap" for OpenWRT's x86 "flavor" is 511 Sectors (Sectors 2 - 511, 512 is the beginning of the first partition, AKA /boot Partition). That's just how it is for OpenWRT because it is what they decided. And just as a historical note, the "MBR Gap" is almost twice as big as the entire capacity of a Commodore 1541 disk (single sided is 170K).

*If conv=sync is used an out of space error will occur.

@@ Line 4: / Line 4: @@
 Copy the MBR (GRUB Stage 1 and Partition Table): <code>dd if=/dev/sdX of=/dev/sdY bs=512 count=1</code>
-Copy the (GRUB Stage 1.5, containing the CORE.IMG file): <code>dd if=/dev/sdX of=/dev/sdY bs=512 skip=1 count=511</code>
+Copy the "MBR Gap" (GRUB Stage 1.5, containing the CORE.IMG file): <code>dd if=/dev/sdX of=/dev/sdY bs=512 skip=1 count=511</code>
 Copy the First Partition (/boot Directory): <code>dd if=/dev/sdX1 of=/dev/sdY1 bs=128M  conv=noerror progress=status</code>
@@ Line 12: / Line 12: @@
 Flush any buffered information to disk: <code>sync</code>
-Notes;
+Syntax Notes;
 *if: Input File (or Device)
@@ Line 20: / Line 20: @@
 *progress = status: Show the progress of the copy process (only for a certain version of DD and up)
 *sync: Write all buffered blocks to disk (just to be safe)
+Other Notes
+*Copying the MBR and MBR Gap can be combined into a single step (it was done to clarify and make an explicit point that there is important code stored in the MBR Gap necessary to boot OpenWRT with GRUB): <code>dd if=/dev/sdX of=/dev/sdY bs=512 count=512</code>
+*The "MBR Gap" for OpenWRT's x86 "flavor" is 511 Sectors (Sectors 2 - 511, 512 is the beginning of the first partition, AKA /boot Partition).  That's just how it is for OpenWRT because it is what they decided.  And just as a historical note, the "MBR Gap" is almost twice as big as the entire capacity of a Commodore 1541 disk (single sided is 170K).
 *If conv=sync is used an out of space error will occur.