Monitor networks and transfer files

ping - Send an ICMP ECHO_REQUEST to network hosts

  • The ping command sends a special network packet called an ICMP ECHO_REQUEST to a specified host. Most network devices receiving this packet will reply to it, allowing the network connection to be verified.
  • Usage: ping <host>
  • Example:
    • ping google.com

traceroute - Print the route packets trace to a network host

  • The traceroute program lists all the “hops” network traffic takes to get from the local system to a specified host.
  • Usage: traceroute <host>
  • For routers that provided identifying information, we see their hostnames, IP addresses, and performance data, which includes three samples of round-trip time from the local system to the router. For routers that do not provide identifying information, we see asterisks.
  • Example:
    • traceroute linux.org

dig - Domain Information Groper

  • It is used for retrieving information about DNS name servers.
  • Usage: dig [server] [name] [type]
  • Examples:
    • dig linux.org
    • dig linux.org MX
    • dig linux.org ANY

ip - Show/manipulate routing, devices, policy routing, and tunnels

  • The ip program is a multipurpose network configuration tool that makes use of the full range of networking features available in modern Linux kernels.
  • It replaces the earlier and now deprecated ifconfig program.
  • You can deactivate or activate interfaces using down or up.
  • IP command guide
  • Example:
    • ip a
    • ip link set dev eth0 up
    • ip link set dev eth0 down

ifconfig

  • Deprecated but still used by many, ifconfig command is used to configure the kernel-resident network interfaces.
  • Usage: ifconfig [...OPTIONS] [INTERFACE]
  • You can activate or deactivate interfaces using up or down options.
  • Examples:
    • ifconfig
    • ifconfig wlan0
    • ifconfig wlan0 down
    • ifconfig wlan0 up

iwconfig

  • Like ifconfig, iwconfig is also used to configure the kernel-resident network interfaces. But it is dedicated to wireless networking interfaces only.
  • It is used to set the parameters of the network interface that are particular to the wireless operation like SSID, frequency etc.
  • Usage: iwconfig [INTERFACE] [OPTIONS]
  • You can set operating mode of the device using mode option. The modes can be Ad-Hoc, Managed, Master, Repeater, Secondary, and Monitor.
  • Examples:
    • iwconfig
    • iwconfig wlan0 mode Monitor
    • iwconfig wlan0 mode Managed

netstat - Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships

  • The netstat program is used to examine various network settings and statistics.
  • Using the -ie option, we can examine the network interfaces in our system.
  • Using the -r option will display the kernel’s network routing table.

ftp - File Transfer Protocol

  • It is used to transfer files over a network.
  • It is not secure as it sends account names and passwords in clear text.
  • By default it runs on port 21.
  • Usage: ftp [fileserver]
  • You can use cd inside FTP prompt to change the directory and lcd inside FTP prompt to change the local directory.
  • Use get to download files to local system and put command to upload files to the server.
  • To download multiple files from the server use the mget command.
  • Example:
    • ftp ftp.ubuntu.com

wget - Non-interactive network downloader

  • It is used to download content from both web and FTP sites.
  • Usage: wget [OPTIONS] [URI]
  • Example:
    • wget https://karthikuj.github.io/images/7uring.png

ssh - Secure SHell

  • It is a remote login and administration program.
  • Before SSH, Telnet was used for the same purpose but it wasn't secure because the communication was in plaintext.
  • By default in runs on port 22.
  • Usage: ssh [username@][server]
  • You can also execute a single command on the system instead of opening a shell session like this - ssh tim@avicii.com ls
  • it is possible to launch and run an X client program (a graphical application) on a remote system and have its display appear on the local system, like so - ssh -X remote-sys and in the shell session that opens just start a GUI application such as xload. On some systems, you may need to use the -Y option rather than the -X option to do this.

scp - Secure Copy

  • It is used to securely copy files between remote hosts and local hosts
  • Usage:
    • scp source destination
    • scp [username@][server:]path [username@][server:]path
  • Examples:
    • scp remote-sys:document.txt .
    • scp bob@remote-sys:document.txt .

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