Re: Extended Linux partition

Albert Cahalan (
Mon, 2 Oct 1995 13:58:13 -0400

> it might be a good idea to work around this problem in Linux by creating
> a new partition type: Linux extended partitions. It would work exactly
> the same as the normal DOS extended partitions, but a different partition
> type byte would not confuse the DOS FDISK program.

Or not so trivial: use 64-bit linear sector numbers in
a fixed table with room for 16+ partitions.

> The change in linux/drivers/block/genhd.c seems trivial to me. Now here
> is another, less trivial idea: to work around the limitations of the
> standard PC partitioning system, maybe it should be possible to add
> (or remove) partitions dynamically at run time? All that is necessary
> at boot time is the root partition, the rest can be added later by some
> special program reading some partition config file and using some new
> ioctl calls on /dev/[hs]d?. That might also be useful for removable
> disks like SyQuest (but I don't have one: how are they handled now?).

This is a very good idea, /dev/vbd?, the virtual block device.
Any contiguous group of sectors can become a block device.
This lets an unfragmented file (say, the Windows swap file)
become a swap _partition_ with full speed advantages or an
ext2 partition inside a floppy disk image. Access to the virtual
block device does not go through the filesystem it resides on.