MOST USED
| ls | List files in directory |
| ls -a | List all files, including hidden ones |
| pwd | Show the directory currently working in |
| mkdir [directory] | Create a new directory |
| rm [file_name] | Remove a file |
| cd [directory] | Change working directory |
| mv [file] [destination] | Move file to new destination |
| cp [file] [destination] | Copy file to new destination |
| grep [PATTERN] [FILE] | Find lines containing [PATTERN] in [FILE] |
| less [filename] | Display the contents of a file or a command output one page at a time |
FILE COMMANDS
| ls | List files in directory |
| ls -a | List all files, including hidden ones |
| pwd | Show the directory currently working in |
| mkdir [directory] | Create a new directory |
| rm [file_name] | Remove a file |
| rm -r [directory_name] | Remove a directory and files recursively |
| rmdir | Remove an empty directory |
| cp [file_name1] [file_name2] | Copy the contents of the first file to a new destination, which can be in a second folder |
| cp -r [directory_name1] [directory_name2] | Recursively copy the contents of the first directory into the second directory |
| mv [file_name1] [file_name2] | Move file_name1 to file_name2 |
| ln -s /path/to/[file_name] | [link_name] Create a symbolic link to a file |
| touch [file_name] | Create a new file |
| head [file_name] | Show the first 10 lines of a file |
| tail [file_name] | Show the last 10 lines of a file |
| gpg -c [file_name] | Encrypt a file |
| gpg [file_name.gpg] | Decrypt a file |
| wc | Print the number of words, lines, and bytes in a file |
FILE COMMANDS (CONT.)
| tar | Stands for for tape archive and is used used to create archive and extract archived files |
| tar -cf | Create an archive with a given file name |
| tar –xvf [file_name] | Unarchive an archive. -x includes the eXtended attributes of the files (metadata) -v is verbose mode -f tells tar what file/archive you are unarchiving |
| mv [file name] /path/to/new/location | Move a file to a new directory |
| cat [file1][file2] | Concatenate files and output |
| di [file_name_1] [file_name_2] | File compare, line by line (note: di is whitespace sensitive) |
| echo [text]>>[file_name] | Echo prints arguments to standard output, ‘>>’ redirects standard output to append to a file [file_name] defines target file name |
| locate [file_name] | Locate a file in the file system |
| curl [options] [URL] | Curl is used for transferring data from or to a server without user interaction. Curl is used to download or upload data using HTTP, HTTPS, SCP , SFTP , or FTP . |
| wget [URL] | Download a file from a server |
NETWORK DIAGNOSTIC COMMANDS
| ifconfig/ip | Get the IP address, MAC address, and MTU of available networks |
| ping [address] | Send ICMP ECHO_REQUEST packets to network host at [address] |
| nslookup [address] | Use the IP address to discover a domain name, or vice versa. |
| nettop | Monitor network activity, showing a list of processes and corresponding process IDs with network connections |
| netstat | Display which ports are active on your machine, their status, and what they’re connected to |
| dig [record type] [domain] | Gather information about a particular domain. Try “dig txt google.com” |
NETWORK DIAGNOSTIC COMMANDS (CONT.)
| hostname | Display hostname of computer |
| hostname –I (capital ‘i’ not lowercase “L”) | Display all IP addresses of computer |
| ifdown [options] -a|[device] | Shutdown network interface |
| ifup [options] -a | [device] | Start a network interface |
| traceroute [host] | Perform traceroute to [host] |
DIRECTORY NAVIGATION
| cd or cd ~ | Go directly to home directory |
| cd .. | Move up one directory level |
| cd [/path/to/directory] | Go directly to directory |
| cd – | Navigate to the previous directory level |
| cd / | navigate to root directory |
SSH (LOGIN)
| ssh [IP address] | Connect to a host |
| ssh user@server | Connect to a server (default port 22) |
| ssh user@server -p other_port | Use a specific port declared in sshd_config |
| ssh user@server [command to run] | Run a command on a remote server |
| ssh-copy-id hostname_or_IP | Copy a unique key pair to server |
| ssh -i ~/.ssh/specific_ssh_fkey | Specify other ssh key for connection |
PIPES/REDIRECTION
| > | Represents output redirection and redirects output to a file and overwriting the file |
| >> | Redirects output to a file and appends the redirected output rather than overwrites |
| < | Represents input redirection and redirects the given input file |
| << | Launch a file and and captures user input until EOF |
| | (ex. command_1 | command_2 | command_3) | A Linux pipe is a form of redirection used to combine two or more commands where the output of one command acts as the input of the next command in the sequence. |
SYSTEM INFORMATION
| lshw | less | List all hardware and pipes to the less command for easy reading and pagination |
| top | Display sorted information about processes |
| free | Free shows system information such as free memory and swap in kibibytes |
| swapon -s | Swap information |
| dmidecode | less | Summarize BIOS information |
| cat /etc/issue | The cat command shows information about a given directory, in this cat /ect/ issue. |
| lspci (or -v for verbose) | Show information about all PCI |
| lsusb (or -v for verbose) | Show information about all usb devices. |
| df –m | Display free storage in megabytes |
| du | Return disk usage |
| du –h [directory] | Return disk usage in a readable file size format Eg. 1.1K or 15M 1.5G (-m shows file in megabytes and -g shows a file in gigabytes) |
| sudo systemctl restart [service_name] | Restart a service Eg. sudo systemctl restart apache2 |
| kill [pid] | Terminate a process. Use the ‘top’ command to find the pid of a process |
| pstree | Display a tree of running processes |
| pmap –x PID [pid] | Display memory information about a process |
| cat /proc/cpuinfo | Display detailed information about the CPU |
USER CONTROLS AND MANAGEMENT USER WARNING: SOME OF
THESE COMMANDS CAN BE DANGEROUS. USE WITH CAUTION.
| useradd [user_name] | Create a new user |
| useradd –r [user_name] | Delete a user |
| passwd | Change your password |
| chown user:group /path/to/file | Change ownership of a file |
| chown –R user:group /path/to/directory | Change the ownership of a directory and files |
| chmod [permission] [file_name] | Change the permissions of a file Eg. chmod 777 /path/to/file |
| quit | Logout |
| w | Display currently logged in users |
| chroot [path] [command] | Change the root directory of a process |
| finger [username] | Display information about a user |
| groups [username] | Display the groups a user belongs to |
| sudo passwd root | Set a new password for the root user, can be used to circumvent the sudo command |
| (sudo) service ssh start | Start ssh service |
| (sudo) service ssh status | Check ssh service status |
| (sudo) service ssh stop | Stop ssh service |
| (sudo) service ssh restart | Restart ssh service |
OTHER
| history | Display prior used commands |
| [tab] | Autocomplete command you are typing, if autocomplete has been configured for your shell session. |
| man [command name] | Display the manual or help file for a command |
| clear | Clear all information from the terminal window. Not useful for security. |
| env | Display environment variables |
| export [variable_name]=[variable_value] | Create a new environment variable |
| unset [variable_name] | Remove environment variable |
| at [-V] [-q queue] [-f file] [-mldbv] TIME | Run a command at a specific time |
| crontab –e | Create a new crontab or edit an existing crontab |
| date | Display current system date and time |
| iostat | List CPU and I/O statistics |
| alias [new command name]=[command] | Create a temporary alias for a command |
| shutdown | Turns a computer off |
| shutdown –r | Reboots a computer |
