HP BL680c XenServer Virtual Machine Installation 4.1.0 - Page 34

Installing Linux VMs • Disks sometimes do not attach correctly on boot (Red Hat Bugzilla 247265) • Live migration can occasionally crash the kernel under low memory conditions (Red Hat Bugzilla 249867) • Guest kernel can occasionally hang due to other xenstore activity (Red Hat Bugzilla 250381) • If you attempt to install RHEL 4.x on a VM that has more than 2 virtual CPUs (which RHEL 4.x does not support), an error message incorrectly reports the number of CPUs detected. To prepare a RHEL4 guest for cloning (see Section 4.6.3, "MAC address"), edit /etc/sysconfig/network-scripts/ifcfg-eth0 before converting the VM into a template and remove the HWADDR line. Note that Red Hat recommend the use of Kickstart to perform automated installations, instead of directly cloning disk images (see Red Hat KB Article 2415). 4.9.3.1. Preparing a RHEL 4.x guest for P2V Before performing a P2V conversion from an existing RHEL4 installation, ensure that the /etc/fstab file in the guest contains an entry for the /boot mount point. This partition contains the files which are changed by the P2V process to give the resulting VM a para-virtual kernel. After a successful P2V, some modifications may be needed in older Red Hat Linux 4.x distributions. In order to get LVM working on xvd* devices, you should add the following line under the 'devices {' line in /etc/ lvm/lvm.conf: types = ["xvd", 16] 4.9.4. Red Hat Enterprise Linux 5 XenServer uses the standard Red Hat kernel supplied with RHEL5 as the guest kernel. Any bugs found in this kernel are reported upstream to Red Hat, and are listed below: • During the resume operation on a suspended VM, allocations can be made that can cause swap activity which cannot be performed because the swap disk is still being reattached. (Red Hat Bugzilla 429102).) • After resuming a suspended VM, it might crash with the message kernel BUG at mm/rmap.c:590! (Red Hat Bugzilla 294811) • Only 3 virtual network interfaces are supported. • Random segmentation faults on loading ELF binaries (Red Hat Bugzilla 247261) • Disks sometimes do not attach correctly on boot (Red Hat Bugzilla 247265). This has been fixed in Red Hat Enterprise Linux 5.1. • Soft lockup messages after suspend/resume or live migration (Red Hat Bugzilla 250994). These messages are harmless, but there may be a period of inactivity in the guest during live migration as a result of the lockup. • Network blackout during live relocation for up to a minute (Red Hat Bugzilla 251527). After migration has completed, the kernel sends a gratuitous ARP to cause ARP caches to get refreshed and minimise network downtime. However, carrier detect is delayed in the kernel and so there is a network blackout until the ARP caches expire or the guest generates an ARP for some other reason. When you install the XenServer xe-guest-utilities RPM, it adds an entry to the yum configuration, allowing you to pick up kernel updates provided by Citrix as they become available. 29