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Re: [Fedora-xen] Slightly off-topic question about Xen+LVM

Aaron Metzger wrote:
Dale Bewley wrote:
Do I need to make a custom boot/initrd script or am I on the wrong track? Ideas are welcome.

Does your initrd contain dm-snapshot.ko?

# cat initrd-2.6.21-2950.fc8xen.img | gunzip | cpio -vt | grep snapshot
-rw-------   1 root     root        34608 Nov 27 08:43 lib/dm-snapshot.ko


No, it does not.

Is the solution as simple as adding it?
If so, what is the procedure to correctly create/build a custom initrd?

"initrd" is built for you when you install the kernel package. The step by step process goes something like this:

(1) When the kernel RPM is installed, an RPM script runs (see 'rpm -q --scripts kernel'):

/sbin/new-kernel-pkg --package kernel --mkinitrd --depmod --install $version

(2) new-kernel-pkg is a shell script which amongst other things runs mkinitrd:

  /sbin/mkinitrd --allow-missing -f $initrdfile $version

(3) mkinitrd is also a shell script which probes the current machine and decides which drivers the machine needs to boot and mount the root filesystem, and combines those drivers and a big shell script together into an initrd image. (Which is a kind of ramdisk available before the kernel has finished booting).

The whole thing is a bit crap to be honest ...

Anyway, if you read the mkinitrd script you'll see that if a dm module other than 'linear' is used in some dmtable entry (see 'dmsetup table' command) then mkinitrd will include the snapshot module, in case it's being used. Actually, on my system mkinitrd appears to be broken so that it never probes for anything in the dmtable at all, so maybe there's a real bug going on here.

You can run new-kernel-pkg at any time to rebuild initrd, and the details above should tell you what's going on. Do file a bugzilla if there is a real problem in mkinitrd script.


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