Networking & remote access

The following are common and useful commands and utilities in Linux for managing networking, networking related functions, and remote access.

1 General networking

Command	Function
/etc/network/interfaces	Location of network interface information
cd dir	Access a directory called dir_name on a remote computer.
curl -O URL	Download contents of a webpage
curl URL	Get or display file from URL
curl ifconfig.me	Find one’s external IP address
dig	Query DNS servers for information on a domain
dig -x IP_address	Check DNS for reverse lookup an active IP address
dig domain	Find DNS information and configuration on an active domain name.
dig@IP domain -t AXFR	DNS Zone Transfer
echo "nameserver /etc/resolv.conf	Add DNS Server
echo "1" /proc/sys/net/ipv4/ip forward	Enable IP Forwarding
ethtool eth0	Query or control network driver and hardware settings
export MAC=MAC_address	Change MAC Address
get file	Download a file from a remote computer to the local machine
host -I hostname	Display the local IP address of a specified hostname with other information.
host -l domain nameserver	DNS Zone Transfer
host IP	Domain Lookup IP
host domain	Display DNS ip address for domain
hostname -i	Display the network address of the host name.
hostname -I	Display all local IP addresses
hostname -I	Display IP address
hostnamectl set-hostname hostname	Manage hostname (/etc/hostname) without restarting
ifconfig	Display the IP and MAC address of a system
ifconfig -a	Display all network interfaces and IP addresses
ifconfig interface IP/CIDR	Set IP and netmask
ifconfig interface mtu size	Change MTU size
ifconfig eth0	Display eth0 address and details
ifconfig eth0 IP up	Activate eth0 with specified IP address
ifconfig eth0 down	Deactivate eth0
ifconfig eth0 up	Activate eth0
ifconfig eth0:1 IP/CIDR	Set virtual interface
ifconfig int hw ether MAC_address	Change MAC Address
ifdown interface	Down an interface
ifup interface	Up an interface
ip a	Display all system IP addresses
ip addr add IP_address dev eth1	Add a temporary IP address to interface eth1
ip addr show	Display network interfaces and their related IP addresses
ip address add IP_address	Used under interface eth0 to assign an IP address.
ip r	Show IP addresses for local host (same as 'route')
lsof -i	Established Connections
mail -s 'mail_subject' -c 'cc-mail_address' -b 'bcc-mail_address' 'to-mail_address'	Send an email from the terminal
nc -vz host port	Scan port in host
netstat -ant	TCP connections
netstat -anu	UDP Connections
netstat -nutlp	Display listening tcp and udp ports and corresponding programs (a netstat command)
netstat -pnltu	Display all listening ports (a netstat command)
netstat -r -v	Prints network routing, information, and connections
netstat -tuln	All tcp and udp listening ports
netstat -tulpn	Connections with PIDs
ping -c hostname	Ping an IP address and stop after a specified number of replies
ping domain/IP	Ping a host by domain name or IP (send ICMP echo request)
ping host-ip	Check connectivity between two hosts
quit	Logout from a remote connection.
route, route -n	Display kernel IP routing table (local host IP addresses)
route add -net IP	Tell other systems which network to route a system on
route add default gw IP	Add a default gateway
route add default gw IP	Set Default Gateway
share user IP c$	Mount Windows Share
smb://IP/sharename	Access Windows SMB Share
ss -tuln	All tcp and udp listening ports
ssh -i	Grants user access to openSSH client.
SSH user@ip_address OR host	Enables SSH login or sign-in to a remote Linux machine by specifying the machine's username and IP address.
tcpdump	Dump network traffic
telnet	Grants access to the Telnet protocol user interface.
traceroute	Show places where packets travel to reach an address
watch ss -tp	Network Connections
wget --random-wait -r -p -e robots=off -U URL	Download an entire website
wget -c file	Continue an interrupted download
wget URL	Download file from a URL, http://domain.com/file
whois domain	Show whois information for a domain

2 Networking: Remote access

Command	Function
/etc/ssh/sshd_config ‘’OR’’ ssh_config	SSHD configuration file (e.g., to change login options or assigned port numbers)
get file	Download a file to a local computer
put file	Upload a file to a remote computer
rsync -a /home /backups/	Synchronize /home to /backups/home
rsync -avz /home server:/backups/	Synchronize files/directories between the local and remote system with compression enabled
scp -r server:/var/www /tmp	Copy all files and directories recursively from server to the current system's /tmp folder.
scp file" server:/tmp	Copy file to a remote server (e.g., into the tmp folder)
scp file" server:/tmp	Secure copy file.txt to the /tmp folder on server
scp user@host:remote local	Copy file from host to local machine
scp server:/var/www/*.html /tmp	Copy *.html files from server to the local /tmp folder.
ssh -i	Open an SSH client; grant user access to SSH client
ssh -p [port user@host	Connect to a remote machine or server through a specified port.
ssh -V	Display SSH version installed on the machine
ssh user@host	Connect to host as user
ssh user@host	Connect to a remote machine or server based on a valid username and hostname or IP address.
SSH user@ip_address OR host	Enables SSH login or sign-in to a remote Linux machine by specifying the machine's username and IP address.
ssh host	Connect to host as user via SSH port (default port 22)
ssh-copy-id -i .ssh/keyfilename.pub user@hostname	Copy public SSH key to remote server
ssh-copy-id user@host	Add current user’s key to host to enable keyed or passwordless login
ssh-keygen -t ed25519 -f ~/.ssh/[filename] -C “[optional comment]”	Generate SSH key on client computer
sudo nano /etc/ssh/sshd_config, PasswordAuthentication no	Disable SSH password login (set PasswordAuthentication to ‘no’, PermitRootLogin to ‘no’, PubkeyAuthentication to ‘yes’)
sudo systemctl reload sshd	Restart SSH server
systemctl status sshd	Show status of SSH server on host machine
telnet host	Uses telnet's default port 23 to connect to a target hostname, remote machine, or server.