UPDATE: I’ve completely rewritten this post. Previously, it was written in such a way as to convey myself as an expert or authority (at least I thought it did). This is most decidedly not the case. The new version below is a writeup of how I went about the upgrade. The main info is identical to the previous post but readers should get a better sense about how knowledgeable (or not) I am.
I wanted to correct my statements from a previous post regarding upgrading to the ext4 file system. In that post I commented that I had problems running fsck.ext3 on certain partitions. This was incorrect. In fact, my problem was with unmounting certain partitions. When I put my desktop system together, I created partitions for a number of different main mount points such as /usr, /var, and /home. The process that I was following from a Debian Admin article went as follows- unmount, fask.ext3, tune2fs and fsck.ext4.
The problem I ran into was in trying to unmount the /usr and /var partitions. I got messages that the operation failed because the device was busy (I was using unmount /dev/hdb# commands). For the /var partition, I was able to hunt down and stop all the processes using fuser and then stopping the appropriate process using /etc/init.d/exim4 stop, for instance. So /var was updated without issue.
The /usr partition proved to be more difficult as I could not stop all of the processes accessing this particular partition. After reading the process for updating the root partition, I decided to try running the tune2fs command without unmounting. It worked. The fsck.ext4 command, however, could not be performed. So I opted to reboot at this time, since I had stopped most of the normal runtime processes anyway. Upon reboot, the fsck alerted me to problems with the partition and basically put me into maintenance mode. Since the partition was not mounted, I was able to run the fsck.ext4 command. Additionally, the root filesystem had been mounted which meant I could access my fstab. So I modified it to specify ext4 for the file system on the partition. I restarted the boot process and everything went off without a hitch.
I got lucky in this case, no 2 ways about it. But the job is done. I haven’t modified the root partition because I’ve been unable to determine if the version of grub2 I’m running (from Debian Squeeze) can handle ext4. Figured it was better not to push my luck.