PatchKernel

Info

• http://wiki.centos.org/HowTos/Custom_Kernel

Patch the kernel

• Mainly to include new hardware drivers (eg 3ware controller)
• prepare
  • download kernel source rpms and install them
  • then (maybe check also if there are no different versions of the kernel source on the machine, so you are sure this spec file is the one you need!)

cd /usr/src/redhat/SPECS
cp kernel-2.6.spec kernel-2.6.spec-orig
rpmbuild -bp kernel-2.6.spec

• • now you have the OS patched kernel in

/usr/src/redhat/BUILD/

• patch
  • 3ware
  • get the drivers you need for your kernel release
  • untar files
  • make a copy of the kernel tree

cd /usr/src/redhat/BUILD/kernel-<version>
cp -R linux-<version> linux2-<version>

• • copy the new 3w-9xxx.c and 3w-9xxx.h files to /usr/src/redhat/BUILD/kernel-<version>/linux2-<version>/drivers/scsi
  • goto /usr/src/redhat/BUILD/kernel-<version> and make the patch with (the order is diff old new

diff -ur linux-<version> linux2-<version> > 3w-<driver version>-<kernel version>.patch

• • copy the 3ware patch file to /usr/src/redhat/SOURCES
  • goto /usr/src/redhat/SPECS and open the kernel-2.6.spec file
  • you need to change the name of the kernel by modifying some version number
    • for centos plus kernels, you can add your own identfer to the %define dist field.
    • locate the last patch in the spec file. Look for the last line which starts with Patch<digits>: <some filename>
    • create a new Patch entry pointing to the 3w patch file you made. the path is relative to /usr/src/redhat/SOURCE
      • don't use any of the Patch999XX ranges, use something lower.
    • locate the equivalent last %patch<digits> entry and insert your new patch %patch<the patchnumber you choose> -p1
  • as an example, for centos 5.1 x86_64, the changes were

[root@fireman SPECS]# diff -u kernel-2.6.spec-orig kernel-2.6.spec
--- kernel-2.6.spec-orig        2008-01-17 12:20:42.000000000 +0100
+++ kernel-2.6.spec     2008-01-17 12:48:06.000000000 +0100
@@ -49,7 +49,7 @@
 # After branching, please hardcode these values as the
 # %dist and %rhel tags are not reliable yet
 # For example dist -> .el5 and rhel -> 5
-%define dist .el5.centos.plus
+%define dist .el5.centos.plus.iihe
 %define rhel 5
 
 # Values used for RHEL version info in version.h
@@ -1601,6 +1601,8 @@
 Patch21841: linux-2.6-ppc-system-cpus-stuck-in-h_join-after-migrating.patch
 Patch21842: linux-2.6-fs-missing-dput-in-do_lookup-error-leaks-dentries.patch
 Patch21843: linux-2.6-net-tg3-fix-performance-regression-on-5705.patch
+
+Patch30000: 3w-9.5.0-2.6.18.patch
 # adds rhel version info to version.h
 Patch99990: linux-2.6-rhel-version-h.patch
 # empty final patch file to facilitate testing of kernel patches
@@ -3191,6 +3193,8 @@
 %patch21841 -p1
 %patch21842 -p1
 %patch21843 -p1
+%patch30000 -p1
+
 # correction of SUBLEVEL/EXTRAVERSION in top-level source tree Makefile
 # patch the Makefile to include rhel version info
 %patch99990 -p1

• you are now ready to rebuild the kernel rpms
  • to build all releases, run

 rpmbuild -bb kernel-2.6.spec >& out

• • this might take a while, you can later check the output file if your patch didn't cause any issues during the build.
    • you can follow the state with

tail -f out

• • • be aware of the following message (it can stop/delay the process).

Not enough random bytes available.  Please do some other work to give
the OS a chance to collect more entropy!

Post config

• since you build a new kernel release, it might be necessary to rebuild depending kernel modules, like XFS
  • install the devel-rpms from your new kernel
  • use rpm -i to keep the current kernel rpms on the box.
  • get and install the source rpms for your modules
  • goto /usr/src/redhat/SPECS and run

rpmbuild --define "kversion <the complete new kernel version>" module.spec

• • eg for centos 5.1 example above with the XFS module

rpmbuild -bb --define "kversion 2.6.18-53.1.4.el5.centos.plus.iihe" kmod-xfs.spec