Thanks, I figured it out, it was missing the LD_LIBRARY_PATH which the script seems to need if you want to launch it without starting it from an existing terminal window. As for the script starting 4 instances of AMDOverdriveCtrl, I had to run that script directly instead of via a new terminal, and then apparently it works fine without terminal windows and without exiting. Some fine hours wasted nitpicking, but finally it works, time to move her to the basement and get a good (silent) night sleep.
If it can be of help to anyone, here are my scripts (modify, launch via start.sh and run 'directly', not in a new terminal):
start.sh#!/bin/bash
./oca.sh &
sleep 5
gnome-terminal -x bash -c "./miner1.sh" &
gnome-terminal -x bash -c "./miner2.sh" &
oca.sh#!/bin/bash
AMDOverdriveCtrl -i 0 gpu1.ovdr &
AMDOverdriveCtrl -i 10 gpu2.ovdr &
AMDOverdriveCtrl -i 3 gpu3.ovdr &
AMDOverdriveCtrl -i 4 gpu4.ovdr &
miner1.sh#!/bin/bash
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH":/path/to/AMD-APP-SDK-v2.4-lnx64/lib/x86_64/"
cgminer -d 0 -c cfg.json --submit-stale
miner2.sh#!/bin/bash
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH":/path/to/AMD-APP-SDK-v2.4-lnx64/lib/x86_64/"
cgminer -d 1 -d 2 -d 3 -c cfg.json -I 8 --submit-stale