> For the complete documentation index, see [llms.txt](https://bryan-guner.gitbook.io/my-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bryan-guner.gitbook.io/my-docs/cheat-sheets/readme/terminal-cheat-sheet.md). # Terminal Cheat Sheet ### 1 – SYSTEM INFORMATION \# Display Linux system information uname -a ## Display kernel release information uname -r ## Show which version of Red Hat installed cat /etc/redhat-release ## Show how long the system has been running + load uptime ## Show system host name hostname ## Display all local IP addresses of the host. hostname -I ## Show system reboot history last reboot ## Show the current date and time date ## Show this month's calendar cal ## Display who is online w ## Who you are logged in as whoami ### 2 – HARDWARE INFORMATION \# Display messages in kernel ring buffer dmesg ## Display CPU information cat /proc/cpuinfo ## Display memory information cat /proc/meminfo ## Display free and used memory ( -h for human readable, -m for MB, -g for GB.) free -h ## Display PCI devices lspci -tv ## Display USB devices lsusb -tv ## Display DMI/SMBIOS (hardware info) from the BIOS dmidecode ## Show info about disk sda hdparm -i /dev/sda ## Perform a read speed test on disk sda hdparm -tT /dev/sda ## Test for unreadable blocks on disk sda badblocks -s /dev/sda ### 3 – PERFORMANCE MONITORING AND STATISTICS \# Display and manage the top processes top ## Interactive process viewer (top alternative) htop ## Display processor related statistics mpstat 1 ## Display virtual memory statistics vmstat 1 ## Display I/O statistics iostat 1 ## Display the last 100 syslog messages (Use /var/log/syslog for Debian based systems.) tail -100 /var/log/messages ## Capture and display all packets on interface eth0 tcpdump -i eth0 ## Monitor all traffic on port 80 ( HTTP ) tcpdump -i eth0 'port 80' ## List all open files on the system lsof ## List files opened by user lsof -u user ## Display free and used memory ( -h for human readable, -m for MB, -g for GB.) free -h ## Execute "df -h", showing periodic updates watch df -h ### 4 – USER INFORMATION AND MANAGEMENT \# Display the user and group ids of your current user. id ## Display the last users who have logged onto the system. last ## Show who is logged into the system. who ## Show who is logged in and what they are doing. w ## Create a group named "test". groupadd test ## Create an account named john, with a comment of "John Smith" and create the user's home directory. useradd -c "John Smith" -m john ## Delete the john account. userdel john ## Add the john account to the sales group usermod -aG sales john ### 5 – FILE AND DIRECTORY COMMANDS \# List all files in a long listing (detailed) format ls -al ## Display the present working directory pwd ## Create a directory mkdir directory ## Remove (delete) file rm file ## Remove the directory and its contents recursively rm -r directory ## Force removal of file without prompting for confirmation rm -f file ## Forcefully remove directory recursively rm -rf directory ## Copy file1 to file2 cp file1 file2 ## Copy source\_directory recursively to destination. If destination exists, copy source\_directory into destination, otherwise create destination with the contents of source\_directory. cp -r source\_directory destination ## Rename or move file1 to file2. If file2 is an existing directory, move file1 into directory file2 mv file1 file2 ## Create symbolic link to linkname ln -s /path/to/file linkname ## Create an empty file or update the access and modification times of file. touch file ## View the contents of file cat file ## Browse through a text file less file ## Display the first 10 lines of file head file ## Display the last 10 lines of file tail file ## Display the last 10 lines of file and "follow" the file as it grows. tail -f file ### 6 – PROCESS MANAGEMENT \# Display your currently running processes ps ## Display all the currently running processes on the system. ps -ef ## Display process information for processname ps -ef | grep processname ## Display and manage the top processes top ## Interactive process viewer (top alternative) htop ## Kill process with process ID of pid kill pid ## Kill all processes named processname killall processname ## Start program in the background program & ## Display stopped or background jobs bg ## Brings the most recent background job to foreground fg ## Brings job n to the foreground fg n ### 7 – FILE PERMISSIONS ![Linux chmod example](https://www.linuxtrainingacademy.com/wp-content/uploads/2017/02/linux-permissions-chart.png) PERMISSION EXAMPLE U G W rwx rwx rwx chmod 777 filename rwx rwx r-x chmod 775 filename rwx r-x r-x chmod 755 filename rw- rw- r-- chmod 664 filename rw- r-- r-- chmod 644 filename ## NOTE: Use 777 sparingly! LEGEND U = User G = Group W = World r = Read w = write x = execute - = no access ### 8 – NETWORKING \# Display all network interfaces and IP address ip a ## Display eth0 address and details ip addr show dev eth0 ## Query or control network driver and hardware settings ethtool eth0 ## Send ICMP echo request to host ping host ## Display whois information for domain whois domain ## Display DNS information for domain dig domain ## Reverse lookup of IP\_ADDRESS dig -x IP\_ADDRESS ## Display DNS IP address for domain host domain ## Display the network address of the host name. hostname -i ## Display all local IP addresses of the host. hostname -I ## Download wget ## Display listening tcp and udp ports and corresponding programs netstat -nutlp ### 9 – ARCHIVES (TAR FILES) \# Create tar named archive.tar containing directory. tar cf archive.tar directory ## Extract the contents from archive.tar. tar xf archive.tar ## Create a gzip compressed tar file name archive.tar.gz. tar czf archive.tar.gz directory ## Extract a gzip compressed tar file. tar xzf archive.tar.gz ## Create a tar file with bzip2 compression tar cjf archive.tar.bz2 directory ## Extract a bzip2 compressed tar file. tar xjf archive.tar.bz2 ### 10 – INSTALLING PACKAGES \# Search for a package by keyword. yum search keyword ## Install package. yum install package ## Display description and summary information about package. yum info package ## Install package from local file named package.rpm rpm -i package.rpm ## Remove/uninstall package. yum remove package ## Install software from source code. tar zxvf sourcecode.tar.gz cd sourcecode ./configure make make install ### 11 – SEARCH \# Search for pattern in file grep pattern file ## Search recursively for pattern in directory grep -r pattern directory ## Find files and directories by name locate name ## Find files in /home/john that start with "prefix". find /home/john -name 'prefix\*' ## Find files larger than 100MB in /home find /home -size +100M ### 12 – SSH LOGINS \# Connect to host as your local username. ssh host ## Connect to host as user ssh user\@host ## Connect to host using port ssh -p port user\@host ### 13 – FILE TRANSFERS \# Secure copy file.txt to the /tmp folder on server scp file.txt server:/tmp ## Copy \*.html files from server to the local /tmp folder. scp server:/var/www/\*.html /tmp ## Copy all files and directories recursively from server to the current system's /tmp folder. scp -r server:/var/www /tmp ## Synchronize /home to /backups/home rsync -a /home /backups/ ## Synchronize files/directories between the local and remote system with compression enabled rsync -avz /home server:/backups/ ### 14 – DISK USAGE \# Show free and used space on mounted filesystems df -h ## Show free and used inodes on mounted filesystems df -i ## Display disks partitions sizes and types fdisk -l ## Display disk usage for all files and directories in human readable format du -ah ## Display total disk usage off the current directory du -sh ### 15 – DIRECTORY NAVIGATION \# To go up one level of the directory tree. (Change into the parent directory.) cd .. ## Go to the $HOME directory cd ## Change to the /etc directory cd /etc | Command | Description | | ------------------------------------- | ----------------------------------------------------------------------------------------------- | | ls | Lists all files and directories in the present working directory | | ls-R | Lists files in sub-directories as well | | ls-a | Lists hidden files as well | | ls-al | Lists files and directories with detailed information like permissions,size, owner, etc. | | cd or cd \~ | Navigate to HOME directory | | cd .. | Move one level up | | cd | To change to a particular directory | | cd / | Move to the root directory | | cat > filename | Creates a new file | | cat filename | Displays the file content | | cat file1 file2 > file3 | Joins two files (file1, file2) and stores the output in a new file (file3) | | mv file "new file path" | Moves the files to the new location | | mv filename new\_file\_name | Renames the file to a new filename | | sudo | Allows regular users to run programs with the security privileges of the superuser or root | | rm filename | Deletes a file | | man | Gives help information on a command | | history | Gives a list of all past commands typed in the current terminal session | | clear | Clears the terminal | | mkdir directoryname | Creates a new directory in the present working directory or a at the specified path | | rmdir | Deletes a directory | | mv | Renames a directory | | pr -x | Divides the file into x columns | | pr -h | Assigns a header to the file | | pr -n | Denotes the file with Line Numbers | | lp -nc , lpr c | Prints "c” copies of the File | | lp-d lp-P | Specifies name of the printer | | apt-get | Command used to install and update packages | | mail -s 'subject' | Command to send email | | -c 'cc-address' | | | -b 'bcc-address' | | | 'to-address' | | | mail -s "Subject" | Command to send email with attachment | | to-address < Filename | | | | | | Linux File Permissions | | | File Permission commands | | | Command | Description | | ls-l | to show file type and access permission | | r | read permission | | w | write permission | | x | execute permission | | -= | no permission | | Chown user | For changing the ownership of a file/directory | | Chown user:group filename | change the user as well as group for a file or directory | | Environment Variables command | | | Command | Description | | echo $VARIABLE | To display value of a variable | | env | Displays all environment variables | | VARIABLE\_NAME= variable\_value | Create a new variable | | Unset | Remove a variable | | export Variable=value | To set value of an environment variable | | User management commands of linux | | | Command | Description | | sudo adduser username | To add a new user | | sudo passwd -l 'username' | To change the password of a user | | sudo userdel -r 'username' | To remove a newly created user | | sudo usermod -a -G GROUPNAME USERNAME | To add a user to a group | | sudo deluser USER GROUPNAME | To remove a user from a group | | finger | Shows information of all the users logged in | | finger username | Gives information of a particular user | | Networking command | | | Command | Description | | SSH username\@ip-address or hostname | login into a remote Linux machine using SSH | | Ping hostname="" or ="" | To ping and Analyzing network and host connections | | dir | Display files in the current directory of a remote computer | | cd "dirname" | change directory to "dirname” on a remote computer | | put file | upload ‘file' from local to remote computer | | get file | Download ‘file' from remote to local computer | | quit | Logout | | Process command | | | Command | Description | | bg | To send a process to the background | | fg | To run a stopped process in the foreground | | top | Details on all Active Processes | | ps | Give the status of processes running for a user | | ps PID | Gives the status of a particular process | | pidof | Gives the Process ID (PID) of a process | | kill PID | Kills a process | | nice | Starts a process with a given priority | | renice | Changes priority of an already running process | | df | Gives free hard disk space on your system | | free | Gives free RAM on your system | | VI Editing Commands | | | Command | Description | | i | Insert at cursor (goes into insert mode) | | a | Write after cursor (goes into insert mode) | | A | Write at the end of line (goes into insert mode) | | ESC | Terminate insert mode | | u | Undo last change | | U | Undo all changes to the entire line | | o | Open a new line (goes into insert mode) | | dd | Delete line | | 3dd | Delete 3 lines | | D | Delete contents of line after the cursor | | C | Delete contents of a line after the cursor and insert new text. Press ESC key to end insertion. | | dw | Delete word | | 4dw | Delete 4 words | | cw | Change word | | x | Delete character at the cursor | | r | Replace character | | R | Overwrite characters from cursor onward | | s | Substitute one character under cursor continue to insert | | S | Substitute entire line and begin to insert at the beginning of the line | | \~ | Change case of individual character |