Day 14: Essential Linux and Git-GitHub Cheat Sheet

File and Directory Management🗂️

• ls: List directory contents.

  • ls -l: List in long format.

  • ls -a: List all files including hidden files (those starting with a dot).

  • ls -lh: Long format with human-readable file sizes

• cd: Change the current directory.

  • Change the directory to [dir]. Use cd .. to go up one level.

• pwd: Print the current working directory.

• mkdir : Create a new directory. mkdir new_folder

• rmdir : Remove an empty directory. rmdir old_folder

• rm : Remove files or directories.

  • rm -r [dir]: Remove the directory and its contents recursively.

  • rm -i [file]: Remove with a prompt before every removal.

File Permissions and Ownership🛡️

• chmod : Change file permissions.

  • Example: chmod 755 script.sh

  • chmod 755 [file_name]: Set permissions to rwxr-xr-x.

  • chmod u+x [file_name]: Add execute permission for the owner.

• chown : Change file owner and group.

  • Example: chown user:group file.txt

• chgrp : Change group ownership.

  • Example: chgrp groupname file.txt

File Permissions Symbols🔑

• r: Read permission.

• w: Write permission.

• x: Execute permission.

• -: No permission.

Viewing and Editing Files📖

• cat : Concatenate and display file contents.

  • Example: cat file.txt

• less : View file contents one screen at a time.

  • Example: less file.txt

• nano : Simple text editor.

  • Example: nano file.txt

• vi or vim : Advanced text editor.

  • Example: vim file.txt

Process Management⏳

• ps: Display current processes.

  • Example: ps aux - Display detailed information about all running processes.

• top: Display and manage processes in real-time.

  • Example: top

• htop: Enhanced version of top (needs to be installed).

• kill: Terminate a process.

  • Example: kill 1234 (terminate the process with PID 1234)

• killall [process_name]: Terminate all processes with the specified name.

• bg: Resume a suspended job in the background.

• fg: Bring a background job to the foreground.

• jobs: List all background jobs.

• systemctl : Manage system services.

  • Example: systemctl start nginx (start nginx service), systemctl status nginx (check status of nginx service)

Networking🌐

• ifconfig: Display or configure network interfaces.

  • Example: ifconfig eth0

• ping [host]: Check the network connection to a server.

  • Example: ping google.com

• netstat: Network statistics.

  • Example: netstat -tuln (List all listening ports.)

• wget [url]: Download files from the web.

• curl [url]: Transfer data from or to a server.

• ip addr: Show IP addresses and network interfaces.

Disk Usage💾

• df: Display disk space usage.

  • Example: df -h human-readable format.

• du: Estimate file space usage.

  • Example: du -sh [file/dir]: Display summary in human-readable format.

Archive and Compression📦

• tar: Archive files.

  • Example: tar -cvf archive.tar folder/ (create), tar -xvf archive.tar (extract)

• gzip: Compress files.

  • Example: gzip file.txt

• gunzip: Decompress files.

  • Example: gunzip file.txt.gz

• zip [archive.zip] [file/dir]: Create a zip file archive.

• unzip [archive.zip]: Extract zip file archive.

Access Control Lists (ACL)🔐

• getfacl [file]: Get the ACL of a file.

• setfacl -m u:[user]:[permissions] [file]: Set ACL for a user.

• setfacl -m g:[group]:[permissions] [file]: Set ACL for a group.

• setfacl -x u:[user] [file]: Remove ACL for a user.

Searching🕵🏻

• grep [pattern] [file]: Search for a pattern in a file.

• grep -r [pattern] [dir]: Recursively Search in a directory.

• grep -i [pattern] [file]: Search Case-insensitive file name .

• find [dir] -name [pattern]: Find files by name.

• locate [name]: Find files by name (uses a database, needs to be updated with updatedb).

Package Management🛒

• apt update: Update package lists but it does not install or upgrade any packages.

• apt upgrade: Installed or upgraded packages.

• apt install [package]: Install a package.

• apt remove [package]: Remove a package.

• apt autoremove: Remove unnecessary packages.

Service Management🛠️

• systemctl start [service]: Start a service.

• systemctl stop [service]: Stop a service.

• systemctl restart [service]: Restart a service.

• systemctl status [service]: Check the status of a service.

• systemctl enable [service]: Enable a service to start on boot.

• systemctl disable [service]: Disable a service from starting on boot.

User Management👨🏻‍💻

• adduser [username]: Add a new user.

• passwd [username]: Change the user password.

• deluser [username]: Remove a user.

• usermod -aG [group] [username]: Add a user to a group.

• groups [username]: Display list the groups a user is in.

Shell Scripting📜

Structure:

  #!/bin/bash
  echo "Hello"

Variables Use:

  #!/bin/bash
  NAME="Ketan"
  echo "Hello, $NAME"

Conditional Statements- If & else:

  if [ condition ]; then
    # Commands
  elif [ condition ]; then
    # Commands
  else
    # Commands
  fi

Loops- For and While:

  for i in {1..5}; do
    echo "Iteration $i"
  done

  while [ condition ]; do
    # Commands
  done

Other Commands 📑

• echo [text]: Display the text.

• date: Display or set the system date and time.

• uptime: Show how long the system has been running.

• who: Show who is logged on.

• history: Show command history.

Configuration🔧

• git config: Set configuration values.

  • Example: git config --global user.name "Your Name",

  • git config --global user.email "you@example.com"

Repository Management📂

• git init: Initialize a new Git repository.

• git clone: Clone a repository into a new directory.

  • Example: git clone https://github.com/user/repo.git

Basic Snapshotting⚙️

• git add: It will move all the files to the staging.

  • Example: git add file.txt

• git commit: It is used to create a new commit with a specific commit message

  • Example: git commit -m "Initial commit"

• git status: Show the working tree status.

• git log: It will display a list of commits.

• git diff: Show changes between two commit IDs and working tree, etc.

Branching and Merging🎋

• git branch: List, create, or delete branches.

  • Example: git branch (list), git branch new-branch (create), git branch -d old-branch (delete)

• git checkout: Switch branches or restore working tree files.

  • Example: git checkout new-branch (switch), git checkout -b new-branch (create and switch)

• git merge: Join two or more development histories together.

  • Example: git merge new-branch

Remote Repositories🍃

• git remote: Manage a set of tracked repositories.

  • Example: git remote -v (list), git remote add origin https://github.com/user/repo.git (add remote)

• git fetch: Download objects and refs from another repository.

  • Example: git fetch origin

• git pull: It will pull the changes from the remote repository to the local.

  • Example: git pull origin main

• git push: Update the remote references along with their associated objects.

  • Example: git push origin main

Rewriting History⌛

• git reset: Reset current HEAD to the specified state.

  • Example: git reset --hard HEAD~1 (delete all commit)

  • git reset --soft HEAD~1(remove from history but store in file system/staging area)

• git revert: Create a new commit that undoes the changes by creating/adding new commits.

  • Example: git revert HEAD

• git rebase: Reapply commits on top of another base tip and it will maintain in a linear format.

  • Example: git rebase main

Additional Tips👀

• .gitignore: Text file used in Git repositories to specify which files and directories should be ignored and not tracked by Git.

  • Example: Add node_modules/ to .gitignore to ignore all files in the node_modules directory.

Conclusion🎯

It provides quick and concise information to help manage files, processes, permissions, and version control efficiently, thereby streamlining workflows and improving the productivity of DevOps Engineers.