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Re: memdisk with debian live

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On Sat, Oct 25, 2008 at 04:26:32PM -0700, Alex Dommasch wrote:
> Hi folks.  I'm new to this list, and pretty new to linux, although I
> used to do a fair amount of work around unix many years ago, so I have a
> grasp of some of the fundamentals.


> then some boilerplate stuff, then
>     "live-initramfs will now start a shell. The error message was:"
>     "  Unable to find a medium containing a live file system"

What happens here is that the live-initramfs[1] scans all accessible
block devices for a live system. This can be on the block device itself
or as a file system image (on a typical USB live system it is a squashfs
image [2]). In your case, it's not finding this.

> Then it left me in BusyBox (took me a while to figure out what that
> was!).  

Welcome to the initramfs environment!

> When I tried using "debian-live-etch-amd64-standard.img", the result was
> very similar, except it didn't have the "no medium found" messages.
> So,.    is debian-live supported running from memdisk?  Is there
> something I can tweak to fix it?  Or is it a non-starter?

Hm. You seem to be almost there. As Daniel (who btw. is much more
knowledgeable tha me in these matters) noted, memdisk is most probably a
detour (and possibly not a very productive one). But it's your call

What is your original reason for using memdisk? Things should work
directly off USB, no?

- ------------------------------------------------------------------------
[1] The initramfs is a minimal Linux system booted from the bootloader.
    An image (typically called initrd.img<something>) is loaded into RAM
    and whatever setup is necessary to get the "real" system up is done.
    This might include:
    * deciding which kernel modules are needed to get hold of the
      device(s) needed to get the root file system
    * Getting raid, logical volumes, whatever together -- whenever the
      root FS "lives" on one of those.
    * asking for a passphrase to cryptographically unlock the
      to-be-mounted root file system;
    * doing whatever necessary to get hold of the network place where
      the root file system is;
    * in the case of Debian live: looking around to find where a root
      file system image is.

    Mostly it is concerned with whatever is necessary to get hold of the
    "real" root file system. After that, life is "normal" and we can
    proceed with the usual init (typically the System V /etc/init.d

    Since space is tight (a typical initramfs image is in the 6..12 MB
    range these days), you get a very restricted environment: busybox,
    etc. Just the tools needed to get this first stage done.

[2] Just "burn" a live system to an USB stick and have a look at that
stick (from Windows, it is a normal DOS file system on it). Under the
directory /live you'll find all those parts.

- -- tomás
Version: GnuPG v1.4.6 (GNU/Linux)


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