In other words how can I run Disk Utility from Terminal when booted in Recovery Mode / off Recovery Partition in recent versions of (Mac) OS X ?
This was once easy; I've remember I figured it out myself in an old version. (Lion?). There's a solution at How to open Disk Utility.app through Terminal? that fails since around 10.8.
Perhaps it's easier to tell Terminal to reopen after a delay and then open Disk Utility?
The executable open can be found on a bootable partition, so
ls -al /Vol*/*/usr/bin/open
should show copies.
Why do this? It's handy to run other things, like