Summary: To get oVirt-managed VMs to boot using PXE, I had to replace
the rhel6-*.rom files with their ipxe equivalents.
Setup: Nodes running CentOS 7, fully current. Engine 3.5.0.1 running
on Fedora 19. Storage via NFS. 1GB ethernet network. DHCP server on
separate subnet, relying on dhcp-relay switch settings.
PXE is our preferred method for installing VMs. We rarely use
templates.
I recently upgraded our oVirt hypervisor nodes from Fedora 19 to
CentOS 7 (where "upgrade" obviously implies a full OS
re-installation). I failed to test creating VMs using PXE in this
setup because -- and this is crucial -- it worked fine on our
non-oVirt CentOS 7 hypervisors, which are managed using virsh and
virt-install.
So PXE booting a new VM failed. The symptom was the dreaded "dhcp
connection timeout" at the seabios prompt. The timout would persist
even when I pressed Ctrl-B and re-tried "dhcp net0" several times over
the course of the next few minutes.
Significantly, existing VMs experienced no DHCP troubles at all, in
the sense that dhclient or its equivalent within the VM could get
and renew leases as expected.
I poked around the forward-delay settings on the oVirt-managed
bridges, but they had the same charactistics of the bridges on our
non-oVirt hypervisors. Lots of other network-oriented troubleshooting
likewise failed.
It got to the point that I took one of my oVirt nodes, removed it from
oVirt, and reinstalled it with plain CentOS 7. Its physical
connections and IP addresses stayed exactly the same. Without oVirt,
virt-install used PXE without a hitch. I re-added that machine to the
oVirt cluster, and PXE failed once again.
I noticed that the BIOS PXE prompt was slightly different in the ovirt
and non-ovirt environment, which led me to poke around the ROM images
in /usr/share/qemu-kvm.
I think the rhel6-*.rom images are those used by oVirt, while the
pxe-*.rom images (actually symlinks into ../ipxe/) are used by, e.g.,
the local virt-install utility.
My workaround is to replace the rhel6-*.rom files with the same
symlinks used by the pxe-*.rom files:
----- %< -----
# short version of script, minus error checking
cd /usr/share/qemu-kvm
for NIC in e1000 ne2k_pci pcnet rtl8139 virtio; do
mv rhel6-${NIC}.rom rhel6-${NIC}.rom.dist
ln -s $(readlink pxe-${NIC}.rom) rhel6-${NIC}.rom
done
----- %< -----
Now oVirt VMs can boot from PXE without any issue.
I'm wildly curious about what's going on here.
--
Paul Heinlein
heinl...@madboa.com
45°38' N, 122°6' W_______________________________________________
Users mailing list
Users@ovirt.org
http://lists.ovirt.org/mailman/listinfo/users
