Red Hat Bugzilla – Bug 432394
guest boot device restrictions unclear
Last modified: 2009-08-20 00:02:16 EDT
The virtualization guide states: Important Restrictions "The guest boot device can not be located on a disk using a para-virtualized block device drivers. However, user data and applications can reside on devices using the para-virtualized block device driver." This is terribly unclear—the phrase "user data and applications" really doesn't *mean* anything, so it doesn't help to clarify what can and cannot be located on a device using para-virtualized block device drivers. Does this mean that only the grub boot device cannot be located on a device using para-virtualized block device drivers? Or does it also mean that the kernel's root target (i.e., the root=DEVICE line argument to the kernel) cannot be located on a device using para-virtualized block device drivers? I suggest that you clarify the restrictions using terms that Linux system administrators commonly understand: the grub boot device, the kernel root=DEVICE device, and any other devices/partitions/volumes (e.g., /lib).
Hi James, We have crafted new guidance documentation for para-virtualized drivers located: http://www.redhat.com/docs/manuals/enterprise/RHEL-5-manual/en-US/RHEL510/html/Para-Virtualized_Drivers/index.html Can you please review and let me know if that answers your questions? Cheers, Mike
Created attachment 296774 [details] editorial suggestions I've reviewed the new guidance documentation. It doesn't answer my question. The specific paragraph I complained about is unchanged. As far as I can tell, the only clarification you added was the following paragraph (at the start of the step-by-step instructions for each OS): "These packages do not support booting from a para-virtualized disk. Booting the guest operating system kernel still requires the use of the emulated IDE driver, while any other (non-system) user-level application and data disks can use the para-virtualized block device driver." Furthermore, the last example in section 8.2 ("8.2. Virtual Storage Devices") lists examples of para-virtualized block devices that are clearly not part of a regular OS install (e.g., "/mnt/pvdisk_xvda"). The phrase "user-level application and data disks" is just as meaningless as "user data and applications". Based on my technical understanding of how the para-virtualized device drivers work, I've rewritten the "Important Restrictions" section of Chapter 2. If my rewrite is technically correct (I think it is, but I'm not certain, which I why I filed this bug in the first place), please consider using it (or something similar to it).
(Null comment to toggle state out of NEEDINFO...)
I have edited and updated these changes but the books may not be made public for a little while. The changes have also been added to the Virtualization Guide for Red Hat Enterprise Linux 5.2. I will forward you some links after these changes have been made public.