Command Description |
Example |
Format |
| Directory List: Lists all files and directory | ls -l | ls -al or ls -l |
| Check connectivity: Test if a system is reachable, i.e. can be connected. | ping 192.168.0.1 | ping <IP Address or Name (with domain) of computer to check> |
| Connect or Login into a remote computer |
telnet 192.168.0.1 |
telnet <IP Address or Name (with domain) of computer to login> |
| Check if POP3 mail server is Up & running |
telnet mail.mydomain.com 110 |
telnet <IP Address or Name (with domain) of computer to login> <Port for POP3 server> |
| Check if SMTP mail server is Up & running | telnet mail.mydomain.com 25 telnet mail.abhikalak.com 25 |
telnet <IP Address or Name (with domain) of computer to login> <Port for SMTP server> |
| Create a local user on Linux system |
useradd -g users -p mypassword myusername |
useradd -g <GroupName or GroupId> -p <Password> <UserName to create> |
| Remove a local user and his/her home directory (including all files) | usrdel -r myusername usrdel -r arun |
usrdel -r <UserName to delete> |
| Become a SuperUser or any other user and change environment variables & home directory according to that user. | su - root | su - <root or any other user> |
| Change Password. SuperUser (root) user can change password of other users by using the second syntax. | passwd passwd arun |
passwd <UserName> passwd -d <UserName> (To delete password) |
| Shutdown the computer. Only SuperUser (root) can give these commands. | init <level> poweroff shutdown |
init 0 poweroff shutdown reboot (To restart machine) |
| To check all Ethernet cards & IPs on your Unix/Linux machine. | ifconfig |
ifconfig --help for other options ifconfig <interface> for a specific interface Typically interfaces in Linux are named like eth0, eth1 for ethernet cards. |
| To check all Ethernet cards & IPs on your Windows machine. | ipconfig /all | ipconfig /? for other options |
Useful Websites |
||
| What Is My IP Address? - IP Address Lookup, IP Address Info, Speed Test, and more: | http://www.whatismyip.com/ | |
| DNSstuff: On-demand DNS and network tools to analyze, diagnose and monitor a domain or IP address: | http://www.dnsstuff.com/ | |
