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  <title>JFS Root Boot HOWTO</title>
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<center><h1>JFS Root Boot HOWTO</h1></center>
Paul Larson <A HREF="mailto:plars@austin.ibm.com">plars@austin.ibm.com</A><br>
v1.0, May 22, 2001 - Copyright &copy; International Business Machines  Corp., 2001
<hr>
1. <A HREF="jfsroot.html#1">Introduction</A><br>
2. <A HREF="jfsroot.html#2">Assumptions/Prerequisites</A><br>
3. <A HREF="jfsroot.html#3">Converting an ext2 based system to JFS</A>
<li>3.1 <A HREF="jfsroot.html#3.1">Build the kernel with JFS support</A>
<li>3.2 <A HREF="jfsroot.html#3.2">Create the JFS filesystem</A>
<li>3.3 <A HREF="jfsroot.html#3.3">Copy the root filesystem</A>
<li>3.4 <A HREF="jfsroot.html#3.4">Final setup</A>
<li>3.5 <A HREF="jfsroot.html#3.5">Reboot</A>

<A NAME="1">
<h3>1. Introduction:</h3>
This HOWTO describes a method for converting an ext2 filesystem based 
Linux system to one running entirely on IBM's Journaled File System (JFS).  
For further information about JFS and to download the latest version of 
JFS, please visit the JFS for Linux web site at  
<A HREF="http://oss.software.ibm.com/developerworks/opensource/jfs/">http://oss.software.ibm.com/developerworks/opensource/jfs/</A>.

<A NAME="2">
<h3>2. Assumptions/Prerequisites:</h3>
Before we get started, there are two assumptions that will be made in 
this document:  
<li>You must already have Linux installed and running  
<li>You must have an empty partition, partitioned as type 83 (Linux).  
It doesn't matter if this partition is formatted or not, but we'll be 
reformatting it as JFS so be prepared to lose anything you might already 
have on it.  
<p>
The examples in this document assume that you just have one big partition 
for your root filesystem and don't have separate mounts for /home, /usr, 
etc.  It's ok if you do have separate partitions for those, but you'll 
need to have enough free space to copy those to the new jfs partition, 
and modify the /etc/fstab file to remove them or change the mount points as 
necessary.  Finally, my root filesystem is on /dev/hda5 and the new 
partition that I'm going to format as JFS is /dev/hda6.  This is system 
specific though, so you'll need to substitute the right partitions from 
your system.  
<p>Something else to consider is that we will need to patch and recompile 
the kernel to add support for JFS.  This isn't hard to do, but if you've 
never recompiled a kernel before, this probably shouldn't be your first 
experience with it.

<A NAME="3">
<h3>3. Converting an ext2 based system to JFS</h3>
No commercial Linux distributions have picked up JFS yet, as it is still 
in beta.  Hopefully soon, building a pure JFS system will be as easy as 
selecting to format your partitions as JFS when you install your 
favorite Linux distribution, but for now this procedure is the easiest 
way to create a system running on JFS.
<p>
The following sections describe the steps necessary to build a JFS root 
filesystem and boot from it.

<A NAME="3.1">
<h3>3.1 Build the kernel with JFS support</h3>
Download the latest 2.4.x kernel from <A HREF="ftp://ftp.kernel.org">ftp.kernel.org</A>, 
and the latest jfs-x.y.z-patch.tar.gz from the 
<A HREF="http://oss.software.ibm.com/developerworks/opensource/jfs">JFS for Linux</A> 
web site to /tmp.  Extract them into separate subdirectories.  Change 
directory into the base directory of the kernel source and patch the kernel.

<pre>
#cd /usr/src
#rm linux
#tar -xvzf /tmp/linux-2.4.3.tar.gz
#mv linux linux-2.4.3
#ln -s linux-2.4.3 linux
#mkdir jfs
#cd jfs
#tar -xvzf /tmp/jfs-0.3.1-patch.tar.gz
#cd /usr/src/linux
#patch -p1 < ../jfs/jfs-2.4.0-v0.3.1-patch
#patch -p1 < ../jfs/jfs-common-v0.3.1-patch
</pre>

Configure the kernel using make config, make menuconfig, or make xconfig 
(whichever you prefer).  In the section labeled "Code maturity level 
options", turn on the item that says "Prompt for development and/or 
incomplete code/drivers."  In the section labeled "File systems" turn on 
the option for "JFS filesystem support."  Make sure to turn on JFS support 
so that it is compiled into the kernel, NOT as a module.  Configure the 
rest of the kernel as needed for your system.  Build the kernel with a 
<tt>make dep; make clean; make bzImage</tt> and if necessary, 
<tt>make modules; make modules_install</tt>.  Then, copy the new kernel into /boot.

<pre>
#make dep
#make clean
#make bzImage
#cp arch/i386/boot/bzImage /boot/vmlinuz-2.4.0-jfs
</pre>

Now we need to build the JFS utilities.  These are the tools for formatting 
a JFS filesystem, checking it for errors, extending the size, and more.

<pre>
#cd fs/jfs/utils
#make
#make install
</pre>

Next, we need to add an entry for LILO so that we can boot with our new 
kernel that can use a JFS filesystem.
Edit /etc/lilo.conf and add an entry for the new kernel similar to this:
<pre>
image=/boot/vmlinuz-2.4.0-jfs
	label=jfsboot
	read-only
	root=/dev/hda5
</pre>

Run <tt>/sbin/lilo</tt> to to activate the new configuration and reboot 
into the new kernel.

<A NAME="3.2">
<h3>3.2 Create the JFS filesystem</h3>
Now that we have JFS support in the kernel, it's time to format our 
empty partition as JFS.
<pre>
#mkfs -t jfs /dev/hda6

mkfs.jfs development version: $Name: v0_3_1 $

Warning!  All data on device /dev/hda6 will be lost!

Continue? (Y/N) y
   \

Format completed successfully.

5120608 kilobytes total disk space.
</pre>

<A NAME="3.3">
<h3>3.3 Copy the root filesystem</h3>
This is an easy step and requires very little work on your part, but it 
will take the most time to complete.  First, unmount any NFS, SMB, or 
cdroms that are mounted.  Create a mount point for the new 
JFS partition and mount it.  There are a few things to remember before we 
start copying files.  Don't copy /proc over, but do create a mount point 
for it after you are done. If you didn't or couldn't unmount some of your 
NFS mounts or cdroms, remember to skip them when you do the copy.  Copy 
everything else using <tt>cp -a</tt>.

<pre>
#mkdir /jfsvol
#mount -t jfs /dev/hda6 /jfsvol
#cd /
#cp -a bin etc lib boot dev home usr var [...] /jfsvol
#mkdir /jfsvol/proc
</pre>

<A NAME="3.4">
<h3>3.4 Final setup</h3>
Before we reboot into our new root partition, there are a just a couple of 
final things that need to be done.  First, we need to change the /etc/fstab 
entry for the root partition, but you need to be certain to change the 
right one.  Remember that the fstab file we want to work with is the one 
under /jfsvol/etc.  So edit this file, and look for the line describing 
the root partition.  Mine looks like this:
<pre>
LABEL=/		/	ext2	defaults	1 1
</pre>

We want to change that to say:
<pre>
/dev/hda6	/	jfs	defaults	1 1
</pre>

You can now unmount /jfsvol.

Edit /etc/lilo.conf to point to the new root partition.  I'm 
paranoid, so I like to just copy and paste the one I already have for the 
jfs kernel and modify the root= line to point to the new partition.  
You'll also need to give it a new label.  The new section on my system 
looks like this:
<pre>
default=jfsboot2
...
image=/boot/vmlinuz-2.4.0-jfs
	label=jfsboot2
	read-only
	root=/dev/hda6
</pre>

Make sure that you run 'lilo' again before you reboot.

<A NAME="3.5">
<h3>3.5 Reboot</h3>
Congratulations! If you followed these steps, your system is now 
running completely on JFS.  To verify this, type <tt>mount</tt> and you 
should see output similar to this:
<pre>
/dev/hda6 on / type jfs (rw)
none on /proc type proc (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
</pre>

Assuming everything works well, and you don't want or need to go back to 
your old system, the old root partition can now be reformatted as JFS and 
turned into a /home mount, or anything else you want.
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