Compiling a Module on Debian with Linux Kernel 2.6.29 and Higher with Xen

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Debian, Suse, and other distributions with recent 2.6.29 and higher kernels, package their kernel headers in a new architecture-specific manner, which breaks compatibility with earlier established methods of building modules for kernels.

root@box~# /usr/bin/r1soft-cki
Checking for binary module
..
No binary module found
Gathering kernel information
Gathering kernel information complete.
Creating kernel headers package
Checking '/usr/src/linux-headers-2.6.32-5-common-xen' for kernel headers
Found headers in 'linux-headers-2.6.32-5-common-xen'
Compressing...
uploading kernel package 100% 3863KB 3.8MB/s 00:01
Starting module build...
............................gathering required information...
sending request for kernel module...
kernel module installer failed. (0):
chroot chroot make
make[1]: Entering directory `/'
~~~~~~
make: Entering an unknown directory
make: *** /usr/src/linux-headers-2.6.30-1-common: No such file or directory. Stop.
make: Leaving an unknown directory
make[4]: *** [all] Error 2
~~~~~~
{code}

h1.  


h1.  Cause


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This issue is known to affect Debian, Suse, and other distros using separate architecture-specific module directories in their header packages. Thanks to Chris at Interspire.com for working closely with us to discover a resolution.

The Debian developers have removed the common/architecture specific symlinks for the kernel headers in 2.6.29 and higher, which has broken parts of the kernel module building process, including the R1Soft CDP Agent module:
(refer to here: [http://bugs.debian.org/cgi-bin/bugrepaort.cgi?bug=521515])

Basically, there are now two kernel module directories, both of which contain necessary files:

drwxr-xr-x 4 root root 4096 2010-01-20 05:43 linux-headers-2.6.32-trunk-amd64
drwxr-xr-x 4 root root 4096 2010-01-20 05:47 linux-headers-2.6.32-trunk-common

h2.  


h1.  Resolution


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Copying the contents of these two directories into a temporary directory, with the proper makefile chosen, will allow the r1soft-cki process to compile a module successfully:
\\
{code}
cd /usr/src/
rsync -avz /usr/src/linux-headers-2.6.32-5-xen-amd64/ r1build/
rsync -avz /usr/src/linux-headers-2.6.32-5-common-xen/ r1build/
{code}
\\

Now, point the r1soft-cki utility to use your temporary directory, with the following flags added to the command:

*CDP2*
{code}

# /usr/bin/r1soft-setup --get-module --kernel-dir /usr/src/r1build
{code}\\
\\
\\

After a successful build, you can delete the temporary directory, restart the agent, and enjoy Continuous Data Protection\!
{code}
rm -r /usr/src/r1build
{code}
*CDP2*
{code}
 /etc/init.d/buagent restart
{code}
*CDP3*
{code}
/etc/init.d/cdp-agent restart
{code}