Ubuntu 22.04

mkfs.xfs /dev/vdb
lsof /var
mkfs.xfs /dev/vdb
mv /var/ /var0
mkdir /mnt/newvar/
mount /dev/vdb /mnt/newvar/
rsync -aqxP /var0/* /mnt/newvar/
umount /mnt/newvar
mount /dev/vdb /var

vim /etc/fstab
# /dev/vdb  / xfs  defaults 0 0