Below comon commands that are used within the Linux as well as the Unix OS are displayed. In many cases there is a mystique surrounding the skills of those who practice security as their craft. Yet, many times the reality is these individuals just have a deaper understanding of what the operating system they use can perform.
| Command |
Description |
| alias |
Set and view command aliases. |
| arch |
Print machine architecture. |
| awk |
Pattern scanning and processing language. |
| bash |
Bourne Again SHell. |
| bg |
Move process running in foreground to the background. |
| biff |
Be notified when mail arrives. |
| cat |
Concatenate and print files. |
| cd |
Change directory. |
| chage |
Change user password expiry information. |
| chgrp |
Change group ownership. |
| chmod |
Change file permissions. |
| chown |
Change file and group owner. |
| chroot |
Run command with special root directory. |
| chsh |
Change login shell. |
| clear |
Clear the terminal screen. |
| cp |
Copy files and directories. |
| crontab |
Maintain crontab files. |
| csh |
C shell. |
| cut |
Remove sections from each line of files. |
| date |
Print or set the system date and time. |
| dd |
Convert and copy a file. |
| df |
Print file-system disk space usage. |
| diff |
Find differences between files. |
| dig |
DNS (Domain Name System) lookup utility. |
| dmesg |
Print diagnostic messages from system buffer. |
| dnsdomainname |
Show system's DNS (Domain Name System) domain name. |
| domainname |
Show system's NIS (Network Information System) |
| or YP |
(Yellow Pages) name. |
| du |
Estimate file space usage. |
| echo |
Display a line of text. |
| env |
Run a program in a modified environment. |
| false |
Exit with a status code indicating failure. |
| fdisk |
Disk partition table manipulator. |
| fg |
Move process running in background to the foreground. |
| file |
Determine file type. |
| find |
Search for files in a directory hierarchy. |
| free |
Display amount of free and used system memory. |
| ftp |
FTP client. |
| fuser |
Identify processes using files or sockets. |
| gcc |
GNU C and C++ compiler. |
| grep |
Print lines matching a given pattern. |
| groupadd |
Create a new group. |
| groupdel |
Delete a group. |
| groupmod |
Modify a group. |
| groups |
Print all the groups the user belongs to. |
| gunzip |
Uncompress files compressed using Lempel Ziv encoding. |
| gzip |
Compress files using Lempel Ziv encoding. |
| host |
DNS (Domain Name System) lookup utility. |
| hostname |
Show or set system hostname. |
| id |
Print real and effective user IDs and group IDs. |
| ifconfig |
Configure a network interface. |
| kill |
Terminate a process. |
| ksh |
Korn shell. |
| last |
Show listing of last logged in users. |
| lastlog |
Show last login times of accounts. |
| ln |
Make links between files. |
| ls |
List directory contents. |
| mail |
Send and receive mail. |
| man |
Format and display manual pages. |
| mesg |
Control write access to a terminal. |
| mkdir |
Make directories. |
| more |
Display file contents one screenful at a time. |
| mount |
Mount a file system. |
| mv |
Move and rename files and directories. |
| netstat |
Print network connections routing tables interface statistics |
|
| masquerade |
connections and multicast memberships. |
| nice |
Run a program with modified scheduling priority. |
| nslookup |
Query Internet name servers. |
| passwd |
Change login and password attributes. |
| ping |
Send ICMP ECHO_REQUEST to network hosts. |
| ps |
Report process status. |
| pwd |
Print name of working directory. |
| quota |
Display disk usage and limits. |
| quotaoff |
Turn off file-system quotas. |
| quotaon |
Turn on file-system quotas. |
| repquota |
Summarize quotas for a file system. |
| rm |
Remove files or directories. |
| rmdir |
Remove empty directories. |
| route |
Show or manipulate system routing table. |
| rpcinfo |
Report RPC (Remote Procedure Calls) information. |
| sed |
Stream Editor. |
| setquota |
Set disk quotas. |
| showmount |
Show mount information for an NFS (Network File System) server. |
| shutdown |
Bring the system down. |
| sleep |
Delay for a specified amount of time. |
| sort |
Sort lines of text files. |
| strace |
Trace system calls and signals. |
| strings |
Print printable characters in files. |
| su |
Run a shell with substitute user and group IDs. |
| tail |
Output the last part of files. |
| tar |
Archiving utility. |
| tcsh |
C shell with filename completion and command editing. |
| telnet |
Telnet client. |
| tftp |
TFTP (Trivial File Transfer Protocol) client. |
| traceroute |
Print the route that packets take to a destination host. |
| true |
Exit with a status code indicating success. |
| umount |
Unmount a file system. |
| uname |
Print system information. |
| useradd |
Create a new user. |
| userdel |
Delete user account. |
| uptime |
Print how long the system has been running. |
| vi |
Text editor. |
| w |
Show users that are logged on and what they are doing. |
| wa |
ll Send message to every user's terminal. |
| wc |
Print the number of bytes |
| whereis |
Locate the binary |
| which |
Show the full path of commands. |
| who |
Show users that are logged on. |
| whoami |
Print effective user ID. |
| write |
Send a message to another user. |
| ypdomainname |
Show or set system's NIS (Network Information System)or YP (Yellow Pages) domain name. |
