WARNING! Do Not do this to your systems. This is for informational purposes only. Do this in a virtual machine only. If you do this outside of a virtual machine, your computer will blow up and you will die. You've been warned.
I did in fact do this over SSH which was not safe and not smart. That fact that I did it does not mean any intelligent or knowledgeable person should do so. In fact, they probably wouldn't consider it.
Now, if you do decide to do this such thing without heeding my warning about your own death, then it's time to stop joking. DO NOT follow other guides. I've read many other guides and all of them left out at least one very important step. All of them left out one step listed on the Ubuntu website which renders your system unbootable if not done.
First off, we'll do the more stable upgrade. If you want to use Ext4 then you should be using Jaunty Jackalope (9.04). To get to Jaunty, we first want to update your system to ensure a smooth transition.
sudo aptitude update && sudo aptitude full-upgrade
Now to upgrade to Jaunty.
sudo do-release-upgrade -d
Once this completes, reboot and you will be running the Beta version of Jaunty. Read that again, Beta, not officially released yet. (http://wordnetweb.princeton.edu/perl/webwn?s=beta | second adjective)
Now to upgrade from Ext3 to Ext4. Do not stop half way through the process and read this whole thing first before starting.
To start, we'll do this to non-vital drives. This means not /home, /boot, or /. Anything else is game for the moment. Run 'mount | grep /dev/sd' to see what partitions you have mounted. Your output will look like this.
michael@panther:~$ mount | grep /dev/sd /dev/sda5 on / type ext3 (rw,relatime,errors=remount-ro) /dev/sda1 on /boot type ext3 (rw,relatime) /dev/sda7 on /home type ext3 (rw,relatime) /dev/sda8 on /var/vbox type ext3 (rw,relatime)
According to what I stated and this list, I will only do /dev/sda8 for the moment. We first unmount the device.
sudo umount /dev/sda8
Now we'll set some flags on the device. Almost every guide you will see will set different flags and I'm sure this isn't the absolute best. However, I did grab these from a partition created as Ext4 from the Ubuntu install CD so I assume they're set for a combination of stability and performance.
sudo tune2fs -O has_journal,ext_attr,resize_inode,dir_index,filetype,needs_recovery,extent,flex_bg,sparse_super,large_file,huge_file,uninit_bg,dir_nlink,extra_isize /dev/sda8
As a side note, I've seen it where the ext_attr,resize_inode,needs_recovery options aren't supported. I haven't seen any issues with omitting these.
Now that I set the options on this device, I need to run an fsck on the drive.
sudo fsck -pf /dev/sda8
The flags here:
f - forces the check even if the file system looks clean p - automatically fix (preen) the file system
Now we need to edit /etc/fstab to reflect the change.
sudo vim /etc/fstab ### Find the line relating to the partition you changed # /var/vbox was on /dev/sda8 during installation UUID=3311b3e1-3cfa-48a9-8911-f3ac30bc0afb /var/vbox ext3 relatime 0 2 ### And change the ext3 to ext4 UUID=3311b3e1-3cfa-48a9-8911-f3ac30bc0afb /var/vbox ext4 relatime 0 2 Save/Close - :x
You should reboot at this point to make sure everything is working. If everything is going great, then it's time to move onto the rest of your partitions.
Please note: this is where things get dangerous and your system could stop booting. It is generally recommended to not do this to the root or boot partitions.
Now, we'll tune the next partitions. I did this on /dev/sda1, /dev/sda5, and /dev/sda7. Refer to the mount listing for a reference.
sudo tune2fs -O has_journal,ext_attr,resize_inode,dir_index,filetype,needs_recovery,extent,flex_bg,sparse_super,large_file,huge_file,uninit_bg,dir_nlink,extra_isize /dev/sda1
Edit /etc/fstab as stated above to reflect these changes.
At this point, be nervous. This is a point that was missed in every other guide I read. You need to reinstall GRUB or it won't be able to read your partitions anymore. Make /dev/sda reflect your setup. More than likely, /dev/sda is what you want; unless you want your MBR on your second drive. You most likely don't want to install it to a partition. Remember, you're installing GRUB to the MBR, not creating files on your partition.
This little command will bring your system from not being bootable to being great. I believe you get one reboot before this must be done. When you reboot, your system will do an fsck on these partitions and convert them to Ext4. At this point, the drives are still Ext3.
Now that you've rebooted after installing GRUB to the MBR, do the grub-install command again and reboot again. It's a quick little thing that I've seen help systems.
CONGRATULATIONS! If you're system is still running, then you now have the Ubuntu 9.04 running Ext4.
Your existing files are not using extents however. Your old files will still behave like Ext3 files. New files will take the behavior of Ext4. This will change after you do a defragmentation of your Ext4 file systems. On-line defragmentation is not supported yet and is very unstable. So unstable that I'm not even considering trying it yet. Once Ubuntu officially supports it, I will indeed post something about it.