While snooping around the stock init script, I spotted a variable, home, in the mountdata function standing out from the crowd. After doing some quick tests, the preliminary results are summarised as follows,
Prerequisite: The persistent overlay (.img, .aes or .inf) being on the same partition as the KNOPPIX file.
Functionality: Loading a specific persistent overlay at the boot time.
Usage: knoppix home=/mnt-system/foobar/dummy
*The dirname and basename cannot contain any whitespace characters.
*The basename needs to be unique if there are more than one overlay files in the same folder because the suffix cannot be part of the argument.
Dell PowerEdge R630 8SFF 2.6Ghz 20-Core 128GB Mem 2x10G+2x1G NIC 2x750W PSU
$399.04
Intel XEON E5-2699 V3 CPU PROCESSOR 18 CORE 2.30GHZ 45MB L3 CACHE 145W SR1XD
$45.00
Dell Poweredge R640 Server | 2x Xeon Gold 6132 | 128GB | H730P | 8x HDD Trays
$1849.00
Dell Poweredge R640 Server | 2x Silver 4114 20 Cores | 96GB | 8x 1.8TB Dell SAS
$2749.99
Intel SR2JT Xeon E5-2683 v4 2.10GHz 16-Core CPU Processor
$21.96
Intel Xeon E5-2680 v4 2.4GHz 35MB 14-Core 120W LGA2011-3 SR2N7
$17.99
Intel Xeon Gold 6140 SR3AX 2.3GHz 18-Core Processor CPU
$39.99
Intel Xeon E5-2699v4 SR2JS 2.2GHz 22-Core 55MB 145W Server Processor CPU
$144.95
Dell Precision Tower 7910 | 2x Intel Xeon E5-2643 V3 | 32GB RAM | No HDD | No OS
$179.95
HP Workstation Z640 2x Xeon E5-2623V4 32GB Ram Dual 256GB SSD K420 Linux GA
$234.98