Default [Q] Can't access sdcard in recovery mode

I want to upgrade my GT-P7310 from Samsung's version of Android 4.0.4 to CM 10.2 but I can't get root/su or Clockwork Recovery installed. When I go into recovery mode and select "apply update from external storage" it shows the error:

E:unknown volume for path [/sdcard]

There's an option to "apply update from cache" too, but /cache isn't writable without root.

I tried the downloading option (Odin) too, using Heimdall for Linux, but the recovery images I've downloaded aren't compatible with that (even after repacking from zip to tar.gz).

I also tried Bin4ry's rooting package (v33), but even after fixing the obvious bugs fixed it depends on remounting /system rw which doesn't work.

Does anyone know how to fix the unknown volume error or how to get Odin to work (preferably with Linux (Heimdall) rather than Windows)?