I have a 8GB / partition and free 4TB on the other disk.
First disk's partitions are /dev/sda1 and /sda2 and the second disk's is /dev/sdc.
Is it possible to extend the / partition with the free space of the second disk?
$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 3.9G 0 3.9G 0% /dev
tmpfs 794M 79M 715M 10% /run
/dev/sda2 7.2G 7.2G 0 100% /
tmpfs 3.9G 0 3.9G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
/dev/loop0 98M 98M 0 100% /snap/core/10444
/dev/loop1 98M 98M 0 100% /snap/core/10185
/dev/md0 14T 26M 14T 1% /mnt/zm
tmpfs 794M 0 794M 0% /run/user/1000
