The new HD you got online finally arrived. After you open your computer and install it (and after looking for badblocks), you’ll need to mount it automatically on boot.
Type lsblk or mount to find the device (or dmesg if you’re brave). In my case, it was /dev/sdb1
/dev/sdb1 on /media/dth/HD2 type ext4 (rw,nosuid,nodev,relatime,data=ordered,uhelper=udisks2)
Now get the device’s UUID and type with blkid
/dev/sdb1: LABEL="HD2" UUID="0d256b26-1782-4f3f-b192-468464DjhdS7" TYPE="ext4" PARTUUID="290cdbb5-01"
Then create the folder where the second HD will be mounted.
Time to edit fstab.
And add to the end of the file your new line.
UUID=0d256b26-1782-4f3f-b192-468464DjhdS7 /HD2 ext4 defaults 0 2
If the driver is mounted, umount now.
Finally, test for errors.
No errors found? Awesome, now reboot your machine when you can and check one last time.