If you don’t create a separate home partition while installing Ubuntu, you don’t have to reinstall Ubuntu from scratch. To migrate to a separate home partition after installation, you’ll have to create a new partition (which may require resizing your existing partitions), copy the files from your existing home directory to that partition, and tell Ubuntu to mount the new partition at /home.
- Create a New Partition : use Gparted to shrink and create new partition. Here a tutorial for you.
Copy Home Files to New Partition : copy your files from old home to the newly created partition
sudo cp -Rp /home/* /new-partition-mount-point
Get your new Partition’s UUID: use the command:
Copy the UUID to add it later to the
Add to the fstab:
sudo gedit /etc/fstab
Add the following text to the fstab file on a new line
UUID=New-partition-UUID /home ext4 nodev,nosuid 0 2
Move Home Directory & Restart
Move your current home directory, and create a new, empty home directory which your new partition will be mounted at:
sudo mv /home /home_OLD
sudo mkdir /home
Now restart and check your new configuration, If everything is just perfect then you can completely remove your old home.
sudo rm -rf /home_OLD
For details and more information refer to the Ubuntu wiki: https://help.ubuntu.com/community/Partitioning/Home/Moving