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 Catalyst C9300-24UX-A 24 Port 10G/mGig Copper UPOE Network Switch
$499.00
Cisco WS-C2960X-48FPD-L 48 V07 POE+ GE+2 10G SFP+, LAN BASE 740W w/ C2960X-Stack
$140.00
Cisco Meraki MX250-HW Cloud Managed Security Appliance - UNCLAIMED
$300.00
Cisco Catalyst 9300 48 Port UPoE Gigabit Switch C9300-48U-E C9300-NM-8X (BH)
$674.95
Cisco C3850-NM-2-10G 2 Port Network Exp.Module for 3850
$30.99
Cisco WS-C2960S-F48LPS-L 2960S Series 48 Port Gigabit Switch, 1 Year Warranty
$27.50
Cisco C3850-NM-4-10G 4 Port Network Exp.Module for 3850
$124.90
CISCO SFP-10G-LR SFP TRANSCEIVER MODULE GBIC 10G 10GB SFP - 1 Year Warranty
$39.99
Cisco Catalyst WS-C2960X-24PD-L GigE PoE 370W, 2 x 10G SFP+, LAN Base w/C2960X-S
$114.00
Cisco Nexus N9K-C93108TC-EX 48-Port 10G RJ-45 6x100G QSFP Network Switch W/Ears
$499.99