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)
Cisco GLC-FE-100LX 100BASE-LX SFP Transceiver Module
$15.59
Cisco GLC-FE-100LX-RGD 100BASE-LX SFP Transceiver Module
$17.99
Cisco w/ Green Hologram SFP-25G-SR-S 25G SFP28 SR 850nm 100m LC MMF
$68.99
Cisco Meraki MA-SFP-1GB-SX 1000BASE-SX SFP Transceiver Module
$24.99
Genuine Cisco SFP-10G-SR V03 10GBASE-SR SFP+ Transceiver Module 10-2415-03
$8.00
SFP-10G-SR Original Cisco 10GBASE-SR SFP+ V02 Multi mode Transceiver 10-2415-02
$5.00
Brand New Cisco GLC-LH-SMD 1000BASE-LX/LH SFP Module 1310nm 10km SMF LC
$13.89
Genuine Cisco GLC-TE 30-1475-01 V01 1000BASE-T SFP COPPER RJ-45 100M TRANSCEIVER
$11.90
LOT OF 20 Genuine Cisco SFP-10G-SR V03 10GBASE-SR SFP+ Transceiver Module
$89.00
New HP HPE Aruba J9150D 10G SFP+ LC SR 850nm 300m MMF XCVR Transceiver Module
$49.99