I am running exactly that way. Since the majority of data "bulk" is going to be located in side your users' home folders I migrated my home folder to the HDD.
Assuming you are not using any partition on the HDD for linux currently you can dismount the HDD and make a new home folder partition.
You will need gparted and nano or your own choice of partition tool and text file editor.CAUTION: these instructions have you blindly erasing hard drive space
Open gparted and create a partition for your home folder on the HDD by selecting the hard disk from the list. It should be labeled something like “sda”.
Either format the hard drive as you wish or split up a current partition and make a new home folder partition.
Migrating the Home folder
To migrate your current Home folder to an HDD partition, there are four things that you need to do:
Mount the HDD partition onto a temporary Home location.
Copy the files from your current Home folder to this temporary Home folder.
Relocate the current Home folder
Mount the new Home folder.
- Create a temporary Home folder
Open a terminal and type the following:
sudo blkid
This will display the UUID(a pseudo-random identifier for every each and every partition) of all the partitions. Record down the UUID for the partition that you have created in gparted.
Next, open the fstab file (contains the necessary information to automate the process of mounting partitions
):
sudo nano /etc/fstab
and add the following line to the end of the file.
UUID=xxx-xxxxx-xxxxx /media/home ext4 nodev,nosuid 0 2
Replace the UUID with the UUID value of the external partition
Save (Ctrl + o) and exit (ctrl + x) the file.
Next, create a mount point to make a place to put your file from the SSD onto the HDD:
sudo mkdir /media/home
and reload the updated fstab.
sudo mount -a
- Copy the files from your SSD Home folder to the HDD Home folder
sudo rsync -aXS /home/. /media/home/.
both periods needed(it means "everything")
- Relocate the current Home folder
cd /
sudo mv /home /home_backup
sudo mkdir /home
- Mount the new Home folder
sudo nano /etc/fstab
and change to line which says
UUID=XXXX.XXXXX.XXXX.XXXX /media/home ext4
to
UUID=XXXX.XXXXX.XXXX.XXXX /home ext4
Save(ctrl+o) and exit(ctrl+x) the file.
Lastly, reload the fstab file:
sudo mount -a
remove the back-up copy and regain the space on your SSD
sudo rm -rf /home_backup
This allows the kernel and all the binaries to be run from SSD and you can use the slower HDD to store your bulky data.
Answers excerpted from https://www.tecmint.com/move-home-directory-to-new-partition-disk-in-linux/