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Useful Command on Linux Network Setting

October 6th, 2008 · 1 Comment

I found the following Linux commands are important when we need to repair the network setting on our Linux or Ubuntu system. For us who just regular user of Ubuntu, problems on network connecting through Network Manager or other GUI wireless connection tools is not easy to repair. In fact sometimes Network Manager is intermittently buggy, connecting sometimes and not others. This networking commands benefits all users in case the GUI tools are not working, and is useful for testing a wireless connection during initial installation of wireless drivers since it provides for good debugging output.

Useful Linux Networking Commands

ifconfig – lists IP address (similar to ipconfig in Windows)
iwlist scan – shows wireless networks that are available in the area along with basic encryption information

lshw -C network – Shows interface and driver associated with each networking device
lspci -nn – Shows hardware connected to the pci bus
lsusb – Shows USB connected hardware
lshw -C usb – Additional info on USB related hardware (good for USB dongles)
cat /etc/modprobe.d/blacklist – List modules that will not be loaded by the Operating System at boot time

lsmod – lists currently loaded kernel modules. (Example usage – lsmod | grep ndiswrapper)
route -n – Lists kernel IP routing table — Good for troubleshooting problems with the gateway (netstat -rn = equivalent command)
sudo route add default gw – Example of how to set the default gateway to
sudo route del default gw – Example of how to delete the default gateway setting
sudo modprobe ***** – Loads the kernel module **** . (Example usage – sudo modprobe ndiswrapper, sudo modprobe r818x, sudo modprobe ath_pci)

sudo modprobe -r **** – Unloades the kernel module ****. (Example usage – sudo modprobe -r ndiswrapper)
sudo ifup/ifdown <interface> – Brings up/down the interface and clears the routing table for the specified interface
sudo ifconfig <interface> up/down – Brings up/down the interface for the specified interface
sudo dhclient <interface> – Request IP address from DNS server for specified interface

sudo dhclient -r <interface> – Release IP address associated with specified interface
sudo iptables -L – Lists firewall rules
dmesg | more – Lists boot log — good for troubleshooting problems with modules/drivers not being loaded
uname -r – Displays kernel version

/etc/iftab (Feisty and pre-releases (Edgy, etc)) – /etc/udev/rules.d/70-persistent-net.rules (Gutsy) – File which assigns logical names (eth0, wlan0, etc) to MAC addresses
cat /etc/resolv.conf – Lists DNS servers associated with network connections (Network Manager)
/etc/dhcp3/dhclient.conf – File which sets or modifies dns (domain name servers) settings

From Ubuntuforum

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