Re: [Xen-devel] [RFC 3/6] linux-stubdomain: Build a disk image.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2013-04-19 at 12:58 +0100, Anthony PERARD wrote:
> On 19/04/13 10:26, Ian Campbell wrote:
> > On Wed, 2013-04-17 at 20:09 +0100, Anthony PERARD wrote:
> >> This patch build a disk image intend to be mounted as rootfs by the
> >> stub-domain. It is build using the 'debugfs' tool and make a ext2 fs.
> >
> > You seem to have some vestigial code for building a cpio style initramfs
> > -- what was wrong with that approach? On the face of it that would seem
> > simpler and less "hacky" than the tricks you have to play with debugfs.
> 
> The initramfs were taking more memory for the stub domain, I could not
> go under 40MB, and now, with the disk, it's 34MB the min that the domain
> his willing to run with.

How Odd. Do you know why, it seems they should contain approximately the
same amount of data.

> > [...]
> >> diff --git a/stubdom-linux/extra/initscript
> b/stubdom-linux/extra/initscript
> >> new file mode 100644
> >> index 0000000..122892f
> >> --- /dev/null
> >> +++ b/stubdom-linux/extra/initscript
> >> @@ -0,0 +1,40 @@
> >> +#!/bin/busybox sh
> >
> > This can become the more normal /bin/sh if you put the appropriate
> > symlink in the initrd?
> 
> If I recall correctly, I tryed the symlink, and it was not starting.
> Maybe a hardlink would works.

The symlink not working is a bit strange, I wonder what the underlying
issue is?

> > This stuff all seems pretty exciting, but isn't it rather fragile
> > against differences in e2fstools versions etc?
> 
> Yes, that was the only good enough way to create a disk image as user
> (not root), with an utility present at least on debian.

What is the status of genext2fs these days?

> > I suppose you must have /usr/sbin and /sbin in your $PATH because none
> > of debugfs, mkfs.ext2 and fsck.ext2 appear in my $PATH...
> 
> Yes, I don't remove {,/usr}/sbin from my PATH.

These are not in $PATH for normal users on many (most?) distros (I
expect you have probably added them yourself), so this script won't work
for some proportion of users.

Ian.


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