A proper way to split a partition and move directory

Question

Currently, I have Ubuntu 12.04 set up with the following partitions:

500G disk with LVM
  80GB root
  4GB swap_1

I want to move the folder /opt to a new LV, for example:

500G disk with LVM
  root (80GB)
  swap_1 (4GB)
  lv_opt (200GB)

What is the right way to do this?

Answer 1

1. Go to single user mode to be on the safe side - telinit 1
2. Create opt_lv
3. Format opt_lv
4. Mount opt_lv on /mnt
5. Copy and retain all attributes (archive move) cp -a /opt/* /mnt/*
6. umount /mnt
7. rm -rf /opt/*
8. Add fstab entry to mount opv_lv on /opt
9. mount /opt
10. Go back to multiuser - telinit 3
11. Done!

Answer 2

If everything in /opt is static, which is probably should be, just copy everything to the new partition with rsync or dd or whatever and then modify /etc/fstab to mount the new partition as /opt and reboot.

If it's not static content, you can either stop anything that would be writing to it before the copy, or just boot into single-user mode and do the copy to be safe.