Network-Manager is a daemon that listens to interfaces statuses and selects a configuration based on wireless SSIDs or user interaction. It is not a graphical program by itself, but interacts with graphical user interfaces for control, as well as featuring a tiny commandline interface and controls over dbus, so it is quite flexible. By default, network-manager does a lot on its own, like trying DHCP as soon as you plug in a cable into the network card.
Actually, network-manager should respect manual settings in /etc/network/interfaces, also in textmode. In fact, Knoppix contains a script that changes network-managers configuration entirely via /etc/network/interfaces for use in textmode:
"knoppix-networkmanager".
However, after changing /etc/network/interfaces manually, you need to restart network-manager in order for changes to take effect:
sudo /etc/init.d/network-manager restart
Do NOT use ifup/ifdown if network-manager is running. Network-manager will ignore the lock status of ifup/ifdown, while ifup/ifdown will ignore all settings done with network-managers own control programs.
Using static IP addresses in network-manager works fine as long as there is a physical connection, but unfortunately, network-manager does not seem to keep the set IP address when there is no carrier signal on the network cable.
If you want to use the command-line, you have the option of excluding an interface from being handled by network-manager:
sudo nmcli dev disconnect iface eth0
which makes network-manager stop listening on eth0 at all, so you can work with ifup/ifdown again if you are more used to these.
Or just suspend network-manager:
sudo /etc/init.d/network-manager stop
(which is an alternative to using the "nonetworkmanager" cheatcode in Knoppix).
Because of its user-friendly desktop integration in Gnome and KDE (and LXDE, too), most distros are using network-manager by default nowadays. For commandline experts who are used to configure everything manually via ifconfig and route, it's a little uneasy that a daemon is handling all the network stuff and will override manual settings (except in the aforementioned cases), I agree with that. So I would recommend just booting Knoppix with the "nonetworkmanager" option, or use the tricks above to revert to the non-automatic configuration behaviour.
Regards
-Klaus
Lenovo ThinkPad E580 15.6" Laptop Intel Core i5 8GB RAM 128GB SSD Windows 11
$139.49
Lenovo ThinkPad T495s Laptop AMD Ryzen 5 PRO 3500U 16GB RAM 256GB SSD Windows 10
$249.99
Lenovo Laptop ThinkPad Light Gaming AMD Ryzen 7 PRO 16GB 256GB SSD Windows 11
$261.89
Lenovo ThinkBook 15 Gen 4 Notebook 15.6" FHD Intel Core i7-1255U 8GB RAM
$549.99
Lenovo ThinkBook 15 Gen 4 Notebook 15.6" FHD AMD R7 5825U 16GB RAM 512GB SSD
$529.99
Lenovo - Legion Slim 5 16" Gaming Laptop WUXGA - Ryzen 5 7640HS with 16GB Mem...
$1349.99
Lenovo - Yoga 7 2-in-1 14" 2K Touchscreen Laptop - AMD Ryzen 5 8640HS with 8G...
$749.99
Lenovo Legion Pro 5i 16" Gaming Laptop RTX 4070 8GB i9-13900HX 16GB RAM 1TB SSD
$1369.99
Lenovo ThinkPad T480s Laptop Computer 14" Core i5 8GB RAM 128GB SSD Windows 11
$208.29
Lenovo ThinkPad T14 Gen1 w/Core i5-10210U CPU - 16GB RAM - 256GB SSD - Win10 Pro
$259.99