# w
Shows who all are currently logged in and where they are logged in from. It also shows the load average of the server.
# who
It also shows who is logged in.
# netstat
Shows all current network connections.
# netstat -an
Shows all connections to the server, the source and destination ips and ports.
# netstat -ntul
Shows all the listening sockets.
# route -n
Shows routing table for all ips bound to the server.
# top
Shows live system processes in a formatted table, memory information, uptime and other useful info.
# top -u root
Show processes running by user root only.
# nslookup <domain_name>
Query your default domain name server (DNS) for an Internet name (or IP number).
# traceroute <IP or domain_name>
Displays each host that a packet travels through as it tries to reach its destination. This command is only run by root user.
# tracepath <IP or domain_name>
To trace the route of a packet to the <IP or domain_name>. This command can run by any user. When compare to traceroute, tracepath has only limited options.
# ifconfig -a
Display info of all the network interfaces on the server.
# ifconfig eth0 down
This will take eth0 (assuming the device exists) down, it won’t be able to receive or send anything until you put the device back “up” again.
# ifconfig eth0 up
This would take eth0 up and available to receive or send packets.
# ping <IP or domain_name>
ping sends an ICMP ECHO_REQUEST packet to the specified host. It provides a very quick way to see if a machine is up and connected to the network.
# hostname
Show the system's host name
# findsmb
Used to list info about machines that respond to SMB name queries. findsmb with noargument would find all machines possible. You can also specify a particular subnet to localize search.
# host <domain_name>
Performs a simple lookup of an internet address using DNS.
# dig <domain_name>
The “domain information groper” is a DNS look up tool. This looks up information about <domain_name> in the DNS.
# dig -x <IP>
Looks up the address and returns the associated domain name.
# dig -t MX <domain_name>
TO show MX records of <domain_name>
# dig -t ANY <domain_name>
To view all the record types (A, MX, NS, etc.).
# dig @<dnsserver_name> <domain_name>
By default dig uses the DNS servers defined in your /etc/resolv.conf file. We can use a different DNS server to perform the query, specify it in the command line.
# whois <domain_name>
Used to look up the contact information from the “whois” databases. Also reports IP address and name server of domain as well as creation and expiration dates.
# ftp <IP> [port]
File transfer protocol. Transfers files to another host (insecure).
# telnet <hostname>
Allows to remotely login to a computer. telnet does not encrypt the information it sends. Everything is sent in plain text, even passwords.
# telnet <hostname> [port]
To connect to a host on a certain port. We can easily check wheter a specifc port on a server is listening or not, using telnet command.
# ssh <user_name>@<IP or domain_name> -p [port]
Allows to remotely connect to <IP or domain_name> via [port]. Unlike telnet, all the information in this session are encrypted.
# scp -r <user_name>@<IP or domain_name>:<source_file_path> <local_file_path>
With the scp (secure copy) command you can easily copy from and to a remote computer or between remote computers.
Shows who all are currently logged in and where they are logged in from. It also shows the load average of the server.
# who
It also shows who is logged in.
# netstat
Shows all current network connections.
# netstat -an
Shows all connections to the server, the source and destination ips and ports.
# netstat -ntul
Shows all the listening sockets.
# route -n
Shows routing table for all ips bound to the server.
# top
Shows live system processes in a formatted table, memory information, uptime and other useful info.
Show processes running by user root only.
# nslookup <domain_name>
Query your default domain name server (DNS) for an Internet name (or IP number).
# traceroute <IP or domain_name>
Displays each host that a packet travels through as it tries to reach its destination. This command is only run by root user.
# tracepath <IP or domain_name>
To trace the route of a packet to the <IP or domain_name>. This command can run by any user. When compare to traceroute, tracepath has only limited options.
# ifconfig -a
Display info of all the network interfaces on the server.
# ifconfig eth0 down
This will take eth0 (assuming the device exists) down, it won’t be able to receive or send anything until you put the device back “up” again.
# ifconfig eth0 up
This would take eth0 up and available to receive or send packets.
# ping <IP or domain_name>
ping sends an ICMP ECHO_REQUEST packet to the specified host. It provides a very quick way to see if a machine is up and connected to the network.
# hostname
Show the system's host name
# findsmb
Used to list info about machines that respond to SMB name queries. findsmb with noargument would find all machines possible. You can also specify a particular subnet to localize search.
# host <domain_name>
Performs a simple lookup of an internet address using DNS.
# dig <domain_name>
The “domain information groper” is a DNS look up tool. This looks up information about <domain_name> in the DNS.
# dig -x <IP>
Looks up the address and returns the associated domain name.
# dig -t MX <domain_name>
TO show MX records of <domain_name>
# dig -t ANY <domain_name>
To view all the record types (A, MX, NS, etc.).
# dig @<dnsserver_name> <domain_name>
By default dig uses the DNS servers defined in your /etc/resolv.conf file. We can use a different DNS server to perform the query, specify it in the command line.
# whois <domain_name>
Used to look up the contact information from the “whois” databases. Also reports IP address and name server of domain as well as creation and expiration dates.
# ftp <IP> [port]
File transfer protocol. Transfers files to another host (insecure).
# telnet <hostname>
Allows to remotely login to a computer. telnet does not encrypt the information it sends. Everything is sent in plain text, even passwords.
# telnet <hostname> [port]
To connect to a host on a certain port. We can easily check wheter a specifc port on a server is listening or not, using telnet command.
# ssh <user_name>@<IP or domain_name> -p [port]
Allows to remotely connect to <IP or domain_name> via [port]. Unlike telnet, all the information in this session are encrypted.
# scp -r <user_name>@<IP or domain_name>:<source_file_path> <local_file_path>
With the scp (secure copy) command you can easily copy from and to a remote computer or between remote computers.
