Merge contents of two partitions into one singular partition I have a machine that has a 20GB FS at `/dev/md1` mounted on `/`, and a ~200GB FS at `/dev/md2` mounted on `/home`. A large amount of data will soon be stored in `/var`. How can I merge these two partitions into one larger partition without wiping the system? If this is not easily possible, what is the easiest way to make the larger partition be mounted at `/var` and the smaller be mounted at `/`, without corrupting everything like user data and anything that's already in `/var` up? The machines are running Debian 7.10. While it makes little difference, I'm actually having this issue on two more or less identical machines. I don't have physical access to either of them. They can be restarted as often as necessary as they are not yet "live" or in production.

Ultimately the fix I found was similar to the one @Anthon posted.

I ended up making a directory (`VAR`) in `/home`. I copied the contents of `/var` into that, then changed `/etc/fstab` such that `/dev/md2` was being mounted at `/var`. Then I rebooted the system. When it came back I created a new `/home` directory (now ending up on `/dev/md1`), moved each of the user accounts (sitting in `/var`) into `/home`, and then moved the contents of (what is now) `/var/VAR` into `/var`. Then I restarted the machine to fix issues involving `/var/lock` and `/var/run` being messed up.

While this is very messy, it's the cleanest way I found to resolve the issue, as it avoided having to deal with symlinks and other messes in `/home`.