Seperate /home Partition (advanced)

[phibit]

This is a question about setting up a separate /home directory, but I will preface it by explaining my current setup.

2x500GB RAID1 (mirror) : Ubuntu Karmic install and /home directory
1x200GB spare drive : empty

In upgrading to Lucid (which I am looking forward to), I would like to change my setup to be like this:

2x500GB RAID1 (mirror) : /home directory ONLY
1x200GB drive : / directory for Ubuntu installs and upgrades

My main concern is preserving my /home directory, and all the data inside. The approach I was thinking of is straightforward, but I'm not experienced enough to tell if it will work:

1. Boot into LiveCD, perform a standard Ubuntu Lucid install on the 200GB drive
2. Point the new install to my old /home directory on the RAID drives
3. Boot into my new installation on the 200GB, and delete everything on the RAID array except the /home directory (i.e. get rid of /var /opt /etc/.... Can you do that?)

Are there any concerns I am overlooking? I suspect that the installation process won't properly recognize the RAID array, and I don't want to much this up.

If you guys have any suggestions they'd be much appreciated. Thanks!

[dabl]

It's not clear from your description whether your current /home directory is on its own drive partition, or is embedded with the rest of the filesystem on a single partition.

Regardless, this part of your plan should work:




1. Boot into LiveCD, perform a standard Ubuntu Lucid install on the 200GB drive




This part will not work if your current /home directory is on the same partition with the rest of your Linux filesystem:




2. Point the new install to my old /home directory on the RAID drives
3. Boot into my new installation on the 200GB, and delete everything on the RAID array except the /home directory (i.e. get rid of /var /opt /etc/.... Can you do that?)


In other words, when /home is located on its own separate partition, then you could proceed as you planned, but if the entire Linux system including your /home directory is on a single partition, then you can't just go in and start deleting things and end up with a happy filesystem.

Thoughts:

- Even allowing for the occasional ISO download, you only need 10 or 15GB for the basic Linux filesystem. 200GB is way overkill.

- If your existing data is less than ~180GB, then potentially you could (a) partition your 200GB drive into a 20GB and a 180GB partition, copy your data into the 180GB partition, install Ubuntu into the 20GB partition, and then proceed to repartition/reformat the 500GB RAID set.

- There's no law that says your data has to physically be in the /home directory. Mine lives on partitions with labels like "DOCS", "IMAGES" and "MUSIC" and then I symlink them into my /home folder. That might be a way around your space challenge.

- You're facing a Grub2 maneuver -- hopefully you have a handle on that.

[phibit]

Thanks for the advice, I have taken it into account and decided on the following strategy:

1. Backup my existing /home directory onto another drive.

2. Repartition my RAID1 (2x500GB) array into THREE (3) Parts:
- /dev/md0 : 20Gb segment dedicated to Linux distribution
- /dev/md1 : 2Gb segment dedicated to swap space
- /dev/md2 : 470Gb segment that will be my new /home

3. Create relevant files systems:
- /dev/md0 : ext4 file system
- /dev/md1 : swap space
- /dev/md2 : ext4 file system (** side note: it would be nice if I could access this portion from Windows 7 , any ideas?)

4. Install Ubuntu Lucid on /dev/md0, specifying that /dev/md1 will be swap and /dev/md2 will be /home

5. Enjoy the resulting magic!


Some concerns of mine are:

1. Does it make sense to reconfigure my RAID1 array, and all the file systems, PRE-installation?

2. Will the Ubuntu Lucid installer properly recognize the RAID configurations?

3. Is 20GB enough space for a Linux Install, bearing in mind I will be installing a fair amount of programs?

Your wisdom would be appreciated, please let me know if there are some red flags in what I'm proposing.

Thanks!

[phibit]

Okay, for the record, the installation worked fine, that is the Lucid alternate cd detected all the RAID arrays correctly, I was able to mount md0 as /, md1 as swap and md2 as /home.

Now, there's another problem, which I guess I was warned about but was still unprepared for: GRUB isn't loading... like, at all. No "grub rescue>", nothing. Kind of looks like it doesn't recognize that the drive is even bootable, it just hangs there.

Any suggestions?

[phibit]

Alright, so I finally got this working. Here is a quick how-to.

Goal: RAID1 Setup with Ubuntu Lucid.

/dev/md0 : ext4 mounted as /
/dev/md1 : swap
/dev/md2 : ext4 mounted as /home


Instructions:

Note: the two drives I'm using are /dev/sda and /dev/sdb, but substitute your corresponding devices names.

Format /dev/sda using fdisk, create 3 new partitions (using n). I used 20Gb for /, 4Gb for swap and the rest for /home. Write the changes with 'w'.
use "# sfdisk -d /dev/sda | sfdisk /dev/sdb" to copy the partition tables exactly from sda to sdb.
Use mdam to create the 3 RAID1 devices. Run "sudo apt-get install mdadm", then for each of the corresponding /dev/sda# and /dev/sdb#, run 'mdadm --create /dev/md# --level=1 --raid-devices=2 /dev/sda# /dev/sdb#'.
Reboot into the Lucid Alternate CD, and follow the steps. It should recognize your RAID devices right away. Assign the proper mountpoints for each and install as normal.
Voila. If all goes well you now have a nice clean RAID1 Ubuntu Lucid setup.


Hope this helps.

[phibit]

See this thread:

http://ubuntuforums.org/showthread.php?t=1469169

For follow-up headaches.