echo $var # is the same as...
printf '%s\n' "$var"

echo -n $var # is the same as...
printf '%s' "$var"

Basic Syntax:

find /path/to/search/ -name searchTerm

If you get a bunch of garbage on the screen, send it all to /dev/null:

find /path/to/search/ -name searchTerm 2>/dev/null

Configs are found here.

Pick one, they basically do the same thing:

 ifconfig -a        # Debian net-tools pkg
 ls /sys/class/net  # ls interface names
 ip a
 ip a show
 ip a show eth0

Manually bringing your network up and down (nixCraft has a good explanation):

• Assuming eth0 (change for whichever interface you want to manipulate).

Generic Method:

ifdown eth0   # Turn off eth0
ifup eth0     # Turn on eth0

Use a specific configuration file:

ifdown wlan0  # bring interface down
ifup --interfaces /path/to/file/interface_config_file wlan0

Debian Method (as root):

/etc/init.d/networking restart  # Restarts network interfaces, or stop/start... 
/etc/init.d/networking stop     # Stops network interfaces
/etc/init.d/networking start    # Starts network interfaces

systemctl restart networking    # For those with lovely systemd
systemctl status network        # See status of network systemd

Debian, overview:

• ifup and ifdown control interfaces that are listed in /etc/network/interfaces.
• ifconfig directly controls network interfaces (much like the newer ip command)

The ifupdown package: high-level network configuration

• The ifup and ifdown commands may be used to configure or deconfigure network interfaces based on interface definitions in the file /etc/network/interfaces.
• Example: bring up the network with ifup eth0 based on eth0 configuration in /etc/network/interfaces.
• ifupdown will wrap ifconfig with the network configuration files (i.e., ifdown or ifup will execute ifconfig down or ifconfig up inside it). That means:
  • ifup eth0 will fetch the interface config file and bring up the interface with the correct IP address, mask, routes etc.
  • ifconfig eth0 up would just start the interface with no IP, etc. (important for sniffing in monitor mode because you don't want an IP address, etc.; you want an open broadcase).

The ifconfig command: a low-level network command (and deprecated, sadly)

• An ifconfig up eth0 activates eth0 but does not setup IP addresses, etc.
• An ifup eth0 sets up IP addresses and other options based on the interface's configuration in /etc/network/interfaces.

Usage of the ip command:

• If your distro did not install ifconfig, you can install it in Debian with apt install net-tools.
• Or you can use the horridly ugly syntax for ip (complex and hard-to-understand help can be found here or an easier-to-understand explanation here).
• From the following example you will need to replace the IP and the interface with your own.

[1] Assign an IP address to a specific interface:

ip addr add 192.168.0.100/24 dev eth0

[2] Bring up the interface link (do NOT skip this step or you will get a “Network is unreachable” error!):

ip link set eth0 up

[3] Bring up the interface link:

ip route add default via 192.168.0.1

[1-3] All in one place… looks like this:

ip addr add 192.168.0.100/24 dev eth0
ip link set eth0 up
ip route add default via 192.168.0.1

Note on Persistence: This will only set up your network for your current work session. You'll lose it on reboot.

• ip (like the old net-tools ifconfig stuff) interacts with /etc/network/interfaces, so put all your network configuration information there and just up/down your network with these commands:

/etc/init.d/networking restart  # Restarts network interfaces, or stop/start... 
/etc/init.d/networking stop     # Stops network interfaces
/etc/init.d/networking start    # Starts network interfaces