Please see the file /etc/apt/sources.list
Peruse the Debian method of marking [oldoldstable] [oldstable] [stable] [testing] [unstable] [experimental] and various other kinds.
Then find your installed Knoppix version's (not the Debian Current Version) declaration in the sources file at the very top.
Re-arrange your declarations accordingly. It is simple and common-sense.
Also don't forget to install the security keys by hand.
Can't be done unless you are Superuser.
That is all there is.
$198.00
1U BareMetal pfsense opnsense Router Firewall DNS Server 6x 10GB Ethernet Ports
$149.00
1U Supermicro Server 10 Bay 2x Intel Xeon 3.3Ghz 8C 128GB RAM 480GB SSD 2x 10GBE
$273.00
Supermicro 1U Server X9SRI-F Xeon E5-2640 v2 2.5Ghz 16-Cores / 64GB / No HDD
$149.99
HP Proliant MicroServer (Model: HSTNS-5151) NO HARD DRIVES-Power Tested,
$99.99
SuperMicro Server 505-2 Intel Atom 2.4GHz 8GB RAM SYS-5018A-FTN4 1U Rackmount
$202.49
HP 658553-001 Microserver UNTESTED AS IS NO HDD
$99.99
SuperMicro SuperServer E101-40 E100-9APP Pentium N4200 8GB RAM 150GB SSD Server
$174.98
2U 12 Bay SAS3 SuperMicro Server 6028U-TR4T+ W/ X10DRU-i+ Barebone 12 Caddy RAIL
$299.00
Supermicro 2U Server 12 Caddy Bay 3.5 LFF E ATX Storage Chassis SAS2 6GBPS Rail
$199.00