Debianist Notes: Howto simply configure network card in Debian

Besides presence of eye-candy graphical configurators in Linux, in many situations it is more straightforward to change config files. It is really simple, and below it is shown how to do it.

How to see current network card settings
For brief review of network settings, it is enough to type in command prompt:

# ifconfig
or
sudo ifconfig

And something like this should appear:

lo        Link encap:Local Loopback
          inet addr:127.0.0.1 Mask:255.0.0.0
          UP LOOPBACK RUNNING MTU:16436 Metric:1
          RX packets:104 errors:0 dropped:0 overruns:0 frame:0
          TX packets:104 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:9387 (9.1 KiB) TX bytes:9387 (9.1 KiB)
eth0      Link encap:Ethernet HWaddr 00:0A:E4:53:AA:2D
          inet addr:192.168.1.5 Bcast:192.168.1.255 Mask:255.255.255.0
          UP BROADCAST MULTICAST MTU:1500 Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
          Interrupt:21 Base address:0x2c00

It is evident, that there are two interfaces had been configured: loopback named lo, and conventional Ethernet card eth0.

How to configure network connection in Linux
To do so, you need root privileges and _your_favorite_text_editor, as well as knowledge of which IP address you need to enter.

To find out which network interface need to be configured, type:

dmesg | grep -i Eth

and next strings should appear:

8139too Fast Ethernet driver 0.9.28
eth0: RealTek RTL8139 at 0xdf822c00, 00:15:f2:51:ad:da, IRQ 21
eth0: Identified 8139 chip type 'RTL-8101'

It looks like it is eth0 (because ethernet, 0 - zero device, pretty logical). Here and below it is assumed that interface is eth0

Configuring Linux network with static IP
Just edit the file:

# nano /etc/network/interfaces
or
sudo nano /etc/network/interfaces

For your local network static IPs are surely enough. In particular, for static IP networking you need to enter: IP-address, netmask and gateway. Change /etc/network/interfaces to something like this:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
    address 192.168.1.5
    netmask 255.255.255.0
    gateway 192.168.1.1

In this example, IP-address 192.168.1.5 is set.

Configuring Linux network with dynamic IP addresses
Continue to edit network config:

# nano /etc/network/interfaces
or
sudo nano /etc/network/interfaces

It is simpler here:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

Similarly, network interface can be configured via command line:

#dhcpcd eth0

For this, you should install in Debian aptitude install dhcp3-client.

Configuring DNS nameserver in Linux
If you don't configure DNS, you cannot connect to any Internet resource by it's name. But it's very simple to tweak it: just edit or create file /etc/resolv.conf

# nano /etc/resolv.conf
or
sudo nano /etc/resolv.conf

And type addresses like this:

nameserver 192.168.1.1
nameserver 192.168.2.1

as much as it is need. The word nameserver is required. It is curious, but in fresh Debian installation there is no resolv.conf...

For changes to take place immediately...
... one can reboot the system, or type: