(Updated: Oct 2009)
As of Lustre™ 1.6.0, Lustre supports running the client modules on most current "stock" kernels without the need for patches to the client kernel. Patches are still required to the Lustre server kernel, but since these nodes generally run only Lustre, this is not a major limitation. Pre-built "patchless" RPMs can be found at the Lustre download site.
We strongly recommend that you use a pre-built RPM rather than building your own. However, if you need to run a kernel on the client that is not one of the supported kernels, it is possible to build from source for the kernels listed at the top the Change Log for each release (see Lustre Release Information).
The Lustre configure script will automatically detect the unpatched kernel and disable building the servers.
[lustre]$ ./configure --with-linux=/unpatched/kernel/source
See the Lustre Test Matrix for a list of kernels that are known to work with patchless Lustre clients. Note that Oracle does not test all of these kernel versions with each Lustre release, but it is expected that kernels between the oldest and newest listed versions work with a given Lustre release.
Many NFS-related bugs are also addressed by the patchless client fixes.