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)
Dell PowerEdge FX2 FX2S Enclosure - 4x PowerEdge FC640 w/ 8x Gold 6132 112C 1TB
$2699.99
Dell PowerEdge M620 0F9HJC Blade Server 2*E5-2670 2.60GHz 192GB RAM 2*300GB SAS
$103.99
HP ProLiant BL460c G9 (Gen9) 2x E5-2670V3 12 Core 3.1GHz No Ram or No Drives
$59.98
DELL M630 BLADE SERVER x2 XEON E5-2660V3 @ 2.6GH H730 PERC HDD CADDIES 16GB FC
$50.00
HP ProLiant BL460c Server Blade (2 x CPU) 24GB RAM/No Drives
$45.60
Dell PowerEdge M630 Blade Server 1x Xeon E5-2630 v4 CPU / Motherboard P/N 0R10KG
$69.99
Dell PowerEdge C6400 Blade Server Chassis w/ 2x 2400W PSUs - Preproduction Model
$349.00
Dell PowerEdge FX2s CTO Blade 4 Slot 2U Chassis 2x 2000W
$399.00
Cisco UCS 5108 Blade Server Chassis Enclosure N20-C6508 4x PSU 8x Fans 2x Fabric
$139.99