Re: [NEW FEATURE]Partitions on loop device for 2.6

[bill davidsen]

In article <200401031905.42584.blaisorblade_spam@xxxxxxxx>,
BlaisorBlade  <blaisorblade_spam@xxxxxxxx> wrote:
| Alle 22:04, venerdì 2 gennaio 2004, Bill Davidsen ha scritto:
| > BlaisorBlade wrote:
| > > NEED:
| > > I have the need to loop mount files containing not plain filesystems, but
| > > whole disk images.
| > >
| > > This is especially needed when using User-mode-linux, since to run any
| > > distro installer you must partition the virtual disks(and on the host,
| > > the backing file of the disk contains a partition table).
| > >
| > > Currently this could be done by specifying a positive offset, but letting
| > > the kernel partition code handle this is better, isn't it? Would you ever
| > > accept this feature into stock kernel?
| >
| > UML is on my list of things to learn (as opposed to "try casually and
| > ignore")
| It is something a bit like VMWare. But instead of emulating hardware and 
| running an OS inside that, you run a patched Linux kernel that runs as an 
| userspace process on the host and provides a virtual machine, which must 
| access a virtual disk, which is stored on a file.
| See http://user-mode-linux.sourceforge.net/ for more info.

As noted, I tried it casually, got a kernel to boot and run, and decided
it wasn't a solution to problems I had at the time.

| > but have you considered using NBD?
| I didn't really know what it was, nor it seems useful for this "as is" (I've 
| not really checked). Maybe that sentence means that the server program could 
| do the partition parsing?

NBD = network block device

This allows a user-space program to publish a file which a kernel with
nbd enabled can mount as a device. So you should be able to run fdisk
and partition it, load stuff on it, and generally treat it like a drive.

Take a look at Documentation/nbd.txt, it may be exactly what you want to
provide a "block device" which can be on the same system using the
loopback interface.
-- 
bill davidsen <davidsen@xxxxxxx>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.
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