Despite the Linux kernel having support for so many file systems, not all of them are enabled in RedHat Enterprise Linux 5 by default. This might be well as some of them might not yet classify as “enterprise grade” in the eyes of RedHat, who knows… Luckily, support for missing file systems such as ReiserFS, XFS and JFS can be added easily as outlined below. For this HOW TO, I assume you are running the stock RedHat kernel.

Get an RPM repository
First of all, you need access to an RPM repository. Usually this is your setup CD-Rom or a network-accessible (FTP, HTTP or even NFS) directory. I assume you have this setup already, so let’s proceed to the next step.

Install required packages
You’ll need the toolchain, rpm-build, the glibc and kernel headers as well as the kernel source RPM from redhat. Issue this to see what kernel header version is required for you:

# uname -a
Linux localhost 2.6.18-53.el5 #1 SMP Wed Oct 10 16:34:19 EDT 2007 x86_64 x86_64 x86_64 GNU/Linux

Install them as required using yum:

#yum install rpm-build.x86_64 ncurses-devel.x86_64 gcc.x86_64 redhat-rpm-config unifdef
[ ... output omitted ... ]
=============================================================================
 Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
 gcc                     x86_64     4.1.2-14.el5     base              5.3 M
 ncurses-devel           x86_64     5.5-24.20060715  base              1.7 M
 redhat-rpm-config       noarch     8.0.45-22.el5    base               53 k
 unifdef                 x86_64     1.171-5.fc6      base               15 k
Installing for dependencies:
 cpp                     x86_64     4.1.2-14.el5     base              2.9 M
 glibc-devel             x86_64     2.5-18           base              2.4 M
 glibc-headers           x86_64     2.5-18           base              598 k
 kernel-headers          x86_64     2.6.18-53.el5    base              814 k
 libgomp                 x86_64     4.1.2-14.el5     base               77 k

Transaction Summary
=============================================================================
Install      9 Package(s)
Update       0 Package(s)
Remove       0 Package(s)         

Total download size: 14 M
Is this ok [y/N]:

This will install everything you need to get going in the first place. Now go and get the kernel source RPM, which you’ll find at the RedHat FTP Site. Save it to a temporary directory and install it accordingly:

# mkdir /usr/src/sources && cd /usr/src/sources
# wget ftp://ftp.redhat.com/pub/redhat/linux/enterprise/5Server/en/os/SRPMS/kernel-2.6.18-53.1.6.el5.src.rpm
# rpm -ivh kernel-2.6.18-53.1.6.el5.src.rpm

This will throw some messages at you about a user/group named “brewbuilder” not being there. That means no harm, however you may prefer to create it first. Now everything needed should exist inside your /usr/src/redhat directory. Then run rpmbuild from the redhat tree.

# cd /usr/src/redhat
# rpmbuild -bp SPECS/kernel-2.6.spec
[ ... output omitted ... ]

Enable the file systems
Now you need to initialize the kernel build environment like this from the kernel source tree. You will also need to copy the original kernel config from your current RedHat kernel.

# cd /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64
# cp /boot/config-`uname -r` .config
# make menuconfig

From “menuconfig” navigate to “File systems”, where you enable the missing modules. In my case I select “Reiserfs support”, “JFS” and “XFS” to be included as module (”M” marking). This is especially required if you just want to build the module and copy it over to your locally installed kernel modules directory. I’d recommend to create an RPM for proper upgrade management anyway, however in this case it actually doesn’t matter (except in terms of overhead and performance of course) it you’re using a module or compile it into the kernel. Afterwards I exit from “menuconfig”, not without saving the changes of course.

Compiling and installing the modules the lazy way
Now this is what I call the lazy way… For easy upgrades and package management, I’d strongly recommend you create a fullblown RPM (see next section). However, if you just want to get going, you can compile the modules manually like this:

# cd /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64
# mkdir .tmp_versions
# make fs/xfs/xfs.ko
# make fs/jfs/jfs.ko
# make fs/reiserfs/reiserfs.ko

Then add the modules made to your current module directory like this:

# mkdir /lib/modules/`uname -r`/kernel/fs/reiserfs
# mkdir /lib/modules/`uname -r`/kernel/fs/xfs
# mkdir /lib/modules/`uname -r`/kernel/fs/jfs
# cp ./fs/reiserfs/reiserfs.ko /lib/modules/`uname -r`/kernel/fs/reiserfs
# cp ./fs/xfs/xfs.ko /lib/modules/`uname -r`/kernel/fs/xfs
# cp ./fs/jfs/jfs.ko /lib/modules/`uname -r`/kernel/fs/jfs
# depmod -a

This will leave you with modules suiting your kernel. However, whenever you’re upgrading the kernel package, they may get overwritten, so it’s best to create a kernel rpm and install it as a regurlar package.

Building a full-featured RPM
Before you create your RPM package, it’s recommended you edit the Makefile and replace the EXTRAVERSION header by something meaningful which makes the difference clear.

# cd /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64
# vi Makefile

In this case, I’ve set EXTRAVERSION = -jfsxfsreiserfs_2.6.18_53_1.6. Then simply run this command to create the RPM package:

# cd /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64
# make rpm

Like this you’ll end up with both a new RPM package and a source RPM inside your /usr/src/redhat/RPMS and /usr/src/redhat/SRPMS directories, which can then be installed via rpm or, if integrated with a local yum repository, from yum itself.

Adding new kernel to GRUB.conf and creating Initial Ramdisk
After I installed the custom kernel rpm, I had to run

mkinitrd /boot/initrd-[custom kernel version].img [custom kernel version]

and then create the grub.conf entry for booting the new kernel, e.g.:

title Red Hat Enterprise Linux Server (2.6.18-53.1.6-jfsxfsreiserfs.el5)
root (hd1,0)
kernel /vmlinuz-2.6.18-53.1.6-jfsxfsreiserfs.el5 ro \ root=/dev/VolGroup_ID_30796/LogVol1 rhgb quiet
initrd /initrd-2.6.18-53.1.6-jfsxfsreiserfs.el5.img

and then decide what order I wanted it in the grub.conf listing (or modify the default= parameter).

Don’t forget this step. The custom-kernel install doesn’t do these parts as a RHEL kernel install normally does.

Getting the tools
Of course, the modules themselves serve no practical purpose if you lack the userspace tools to create and maintain the file systems. Get them accordingly from ftp://oss.sgi.com/projects/xfs/ (XFS), http://jfs.sourceforge.net/ (JFS) and http://chichkin_i.zelnet.ru/namesys/ (ReiserFS). Again, it’s recommended to create an RPM from the sources, but this is beyond the scope of this article.

XFS RPM
The easiest and quickest way to support XFS is to install an XFS RPM.

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