I am not sure, what you are intend to do. If you want a new bootable harddrive, I suggest, to clone the old (maybe smaller one) to the new one using clonezilla.
After it you can resize the partitions of new one to your needs and then mount the old one to any folder you want (maybe "/space" or "/data", whatever) Or just format it. If you then want it automatically mounted, I suggest, to enter the device (like "/dev/sdc1") into /etc/fstab, but the UUID. If you are using the devicename, it may happen when several harrdtrives, the BIOS will not recognize the correct order. So /dev/sdc1 is /dev/sdd1 suddenly. (I have 4 harddrives in my computer and ran in this issue) Using UUID will avoid this. An entry in /etc/fstab would then look like this: UUID=XXXXX-XXXX-XXXX-XXXX-XXXXXXXXX /home ext4 defaults 0 Just an example. Dunno, if it is that, what you want. If not, just ignore my mail. Best Hans