shift /var/lib to a new partition

Question

I have a system which completely resides on a (relatively small) single harddrive (/dev/sda). Now I am expecting to /var/lib/ to become populated with more and more files (due to using lxd containers) and therefore I want to shift that to another hard drive or partition which I am adding to the system.

2 methods come to mind and I'd like to get some advice from a little more experienced people which one to favor

METHOD A - symlink

1. sudo cp -a -r /var/lib/ /mnt/new-hd/
2. sudo mv /var/lib /var/old-lib
3. sudo ln -s /mnt/new-hd/lib
4. reboot

METHOD B - mounting new folder over existing /var/lib

1. sudo mnt /dev/new-hd
2. /mnt/temp sudo
3. cp -a -r /var/lib/* /mnt/temp
4. sudo umount /mnt/temp
5. create fstab entry for /dev/new-hd (to be mounted to /var/lib)
6. sudo mount -a

looking at it now. I'm in favor of METHOD B slightly. Any comments?

In my usecase it's about lxd, so I am also wondering whether shifting the entire /var/lib is the best choice for this or should I only move the relevant parts? Mocing the entire /var/lib has the advantage to have a structure which is very similar to the default (and therefore less custom things to be aware of)

Answer 1

If you were building the system from scratch, you'd probably use method B because that's the proper way to spread your file system over multiple physical devices. So if you can do B, I think thats the more-sound approach. I'd only use method A if you were planning to exchange different copies frequently, or needed one copy to exist in two places.

Answer 2

Is it really necessary to perform this operation on a running machine? Why dont you download a livecd of any linux distro, and run the system from cd/usb? You should be able to move the /var/lib to any other location without any problem. Dont forgett to copy/move file permissions.