dracut and multiple ISO's as loopback mounts

dracut and multiple ISO's as loopback mounts

[Jon Stanley]

I'm wanting to loopback mount MULTIPLE iso's that are embedded in the
same initramfs - does dracut currently support this? The use case is
that there is a base OS livecd that I'm embedding in an initramfs, and
that works fine today.

However, on top of that, I want independently versioned additional
content. For example, imagine shipping some ISV content on top of a
generic LiveCD that you intend to PXE boot. The base OS need not
change (and I don't want it to change or to rebuild it).

The commentary in the livecd-iso-to-pxeboot script (part of
livecd-tools - https://git.fedorahosted.org/cgit/livecd/tree/tools/livecd-iso-to-pxeboot.sh)
seems to indicate the kernel will DTRT with it - but will it still
DTRT with multiple (3+) cpio archives?

As a side question, how do you dissect a cpio archive like this? The
standard cpio invocation seems to stop at the end of the first
archive, which makes sense. How do you specify you want the nth
archive out of a single file?

Re: dracut and multiple ISO's as loopback mounts

[Harald Hoyer]

On 10/03/2013 03:51 PM, Jon Stanley wrote:
> I'm wanting to loopback mount MULTIPLE iso's that are embedded in the
> same initramfs - does dracut currently support this? The use case is
> that there is a base OS livecd that I'm embedding in an initramfs, and
> that works fine today.
> 
> However, on top of that, I want independently versioned additional
> content. For example, imagine shipping some ISV content on top of a
> generic LiveCD that you intend to PXE boot. The base OS need not
> change (and I don't want it to change or to rebuild it).


You would have to write such a dracut module on your own.

> 
> The commentary in the livecd-iso-to-pxeboot script (part of
> livecd-tools - https://git.fedorahosted.org/cgit/livecd/tree/tools/livecd-iso-to-pxeboot.sh)
> seems to indicate the kernel will DTRT with it - but will it still
> DTRT with multiple (3+) cpio archives?
> 

I think the kernel unpacks cpio archives as long as it finds one appended to the
last one.

> As a side question, how do you dissect a cpio archive like this? The
> standard cpio invocation seems to stop at the end of the first
> archive, which makes sense. How do you specify you want the nth
> archive out of a single file?

Yeah, someone has to write such a user tool. lsinitrd would benefit from it.