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)
Juniper Networks EX3300 EX3300-48P 48-Port Gigabit PoE+ Switch
$37.21
Juniper Networks EX2300-C-12T Compact 12-Port EX2300-C Series Ethernet Switch
$300.00
Juniper Networks EX3300 EX3300-48P 48-Port Gigabit PoE+ Switch
$59.95
JUNIPER EX4200-24PX 24-Port Gigabit PoE+ Managed Ethernet Network Switch
$49.95
Juniper EX3300-48P 48-Port 10/100/1000BASE-T (48 PoE+ ports) with 4 SFP+
$74.00
Juniper EX2300-C-12P 12-Port Gigabit Ethernet PoE+ 2x SFP+ *NO OS*
$199.99
Juniper Networks EX4300-48T 48 Port Gigabit 4 QSFP 40G 2xPSU AFO Network Switch
$89.00
Juniper EX3300-24P Juniper 24 Port Gigabit PoE+ Switch - Same Day Shipping
$79.99
Juniper EX3300-48P, 48 Port PoE+ Gigabit Network Switch with RACK EARS, RESET
$46.99
Juniper QFX5100-48T-AFO 48 100M/1G/10G Base-T 6 QSFP AFO
$439.00