This message occurring during boot up of KNOPPIX-Live has no deleterious consequences but it is an annoyance.
It is probably an unintended hangover from the HD-installed version which allocates several partitions.
Either ignore it or include a (2nd and) 3rd (and 4th) partition in your boot device, even if it is a USB stick.
Use fdisk* to set /dev/{sda}1 as the KNOPPIX partition type c (being FAT32; or NTFS if you prefer - I've never tried this).
Set /dev/{sda}3 as type 83 (Linux) (at least 400M). Then format it as Reiserfs with mkreiserfs .
It's not obvious to me how (or even whether) the partition is used; but it is made available; and you will boot
without the annoying error message!
(*) Yes: you need to format your intended USB device - from a temporary KNOPPIX USB device is probably your most
convenient method ;o)
A-Tech 8GB DDR3 1600 PC3-12800 Laptop SODIMM 204-Pin Memory RAM PC3L DDR3L 1x 8G
$13.99
HyperX FURY RAM DDR4 16GB 8GB 32GB 4GB 3200 2666 2400 2133 Desktop Memory DIMM
$9.64
Lot of 10 Mixed Major Brands 8GB PC4-2400MHz DDR4 19200 Laptop Memory Ram TESTED
$99.95
A-Tech 16GB 2 x 8GB PC3-12800 Laptop SODIMM DDR3 1600 Memory RAM PC3L 16G DDR3L
$27.98
HyperX FURY DDR4 4GB 8GB 16GB 32GB 3200 2400 2666 Desktop RAM Memory DIMM 288pin
$23.15
CRUCIAL DDR3L 8GB 16GB 32GB 1600 MHz PC3-12800 Laptop Memory RAM SODIMM 204-Pin
$14.85
CORSAIR - VENGEANCE LPX 16GB (2PK x 8GB) 3200MHz DDR4 C16 DIMM Desktop Memory...
$44.99
A-Tech 8GB PC3-12800 Desktop DDR3 1600 MHz Non ECC 240-Pin DIMM Memory RAM 1x 8G
$13.99
Micron 32GB 1Rx4 PC5-4800 EC8 RDIMM DDR5-38400 ECC Registered Server Memory RAM
$99.99
HYNIX HMAA8GL7MMR4N-UH 64GB (1X64GB) 4DRX4 PC4-2400T DDR4 MEMORY
$44.30