Day 12 of #90DaysOfDevOps

Linux Git Cheat Sheet

File System Navigation:

• sudo - Super User Do. The sudo command allows you to run commands with the superuser privileges.

• whoami - Displays currently logged-in user.

• pwd: Print the current working directory.

• ls: List files and directories in the current directory.

  • ls -l: List files and directories in long format.

  • ls -a: List all files and directories, including hidden ones.

• cd: Change the current directory.

  • cd ~: Change to the home directory.

  • cd ..: Move up one directory level.

• touch: Create an empty file.

• mkdir: Create a new directory.

• rm: Remove files or directories.

  • rm -r: Remove directories recursively.

• mv: Move or rename files and directories.

• cp: Copy files and directories.

• find: Search for files and directories.

• grep: Search for text within files.

• cat: Display the contents of a file.

• echo - displaying lines of text or string which are passed as arguments on the command line. Can be used to create a file or empty a file.

  echo "Hello" - prints Hello

  echo "Hello" > hello.txt - Creates a file hello.txt with Hello as content in it.

  echo "World" >> hello.txt - appends the content(World) to the file hello.txt

  echo > hello.txt - Empties the content from hello.txt file.

• stat - Display file or file system status.

• more or less: View file content page by page.

• head and tail: Display the beginning or end of a file.

• sort - The sort command sorts the contents of a file, in numeric or alphabetic order, and prints the results to standard output.

  -h, --human-numeric-sort compare human readable numbers (e.g., 2K 1G)

  -n, --numeric-sort compare according to string numerical value

  -r, --reverse reverse the result of comparisons

• file: Determine file type.

File Permissions:

• chmod: Change file permissions.

• chown: Change file ownership.

• chgrp: Change group ownership.

• umask: Set default permissions for new files and directories.

ACL file permissions:

• getfacl - Get file ACL. This command shows the permission of the file in detailed manner.

• setfacl- set file permission using ACL.

  setfacl -m u:jack:r-- test.txt

  -m - modify, u-user, jack-username, r---read permission, test.txt- file name

  setfacl -x u:jack:r test.txt

  To remove permission for a file from all the user and groups which were added using ACL.

Process Management:

• ps: List running processes.

  • ps aux: List all processes.

• top: Monitor system processes in real-time.

• kill: Terminate processes.

• killall: Terminate processes by name.

• bg and fg: Manage background and foreground processes.

• nohup: Run a command that continues running even after you log out.

Package Management (Debian/Ubuntu):

• apt-get update: Update package lists.

• apt-get upgrade: Upgrade installed packages.

• apt-get install: Install new packages.

• apt-get remove: Remove packages.

• apt-cache search: Search for packages.

• dpkg: Debian package management commands.

Package Management (Red Hat/CentOS):

• yum update: Update packages.

• yum install: Install packages.

• yum remove: Remove packages.

• yum search: Search for packages.

• rpm: RPM package management commands.

Networking:

• ifconfig or ip: Display network interface information.

• ping: Check network connectivity.

• netstat: Network statistics.

• ssh: Securely access remote systems.

• scp: Securely copy files between systems.

• curl or wget: Download files from the internet.

• nc: Netcat for network-related tasks.

• iptables or firewalld: Configure firewall rules.

System Information:

• uname: Display system information.

• df: Show disk space usage.

• du: Show directory space usage.

• free: Display memory usage.

• top or htop: Monitor system resources.

• lscpu or cat /proc/cpuinfo: CPU information.

• lsblk or fdisk -l: List block devices.

• date: Display the system date and time.

Shell Scripting:

• Create and edit shell scripts using a text editor like nano, vim, or emacs.

• Use #!/bin/bash (or another shell) as the shebang line.

• Make the script executable with chmod +x script.sh.

• Execute the script with ./script.sh or bash script.sh

Automation (cron):

• crontab: Schedule recurring tasks.

Text Processing:

• sed: Stream editor for text manipulation.

• awk: Text processing tool.

• cut: Extract sections from lines of files.

Monitoring and Logging:

• Use tools like syslog, journalctl, and logrotate for system logs.