Initial commit

2026-03-05 17:47:01 +01:00
commit 563202f986
20 changed files with 1136 additions and 0 deletions
@@ -0,0 +1,293 @@
+# Linux Essential Commands – Cheat Sheet
+
+Each block groups related commands and includes inline comments so it can be copied and pasted as a whole.
+
+---
+
+## 1. Navigation & Help
+
+```bash
+# Show current directory
+pwd
+
+# List files (basic / long / including hidden)
+ls
+ls -l          # long listing (permissions, owner, size, date)
+ls -a          # include hidden files (starting with .)
+
+# Change directory
+cd /path/to/dir
+cd ~           # go to home directory
+cd ..          # go up one level
+
+# Command help
+man ls         # full manual page
+ls --help      # quick help for a command
+```
+
+---
+
+## 2. Files & Directories
+
+```bash
+# Create or update an empty file
+touch file.txt
+
+# Copy files and directories
+cp source.txt dest.txt
+cp -r src_dir/ dest_dir/    # copy directory recursively
+
+# Move or rename
+mv oldname.txt newname.txt
+mv file.txt /target/dir/
+
+# Remove files and directories
+rm file.txt                 # remove file
+rm -r dir_to_remove/        # remove directory recursively
+rm -rf dir_to_force/        # force remove (use with care)
+
+# Create directories
+mkdir new_dir
+mkdir -p a/b/c              # create nested directories
+```
+
+---
+
+## 3. Viewing & Searching Content
+
+```bash
+# View file content
+cat file.txt                # print whole file
+less file.txt               # scrollable view (quit with 'q')
+
+# View start / end of a file
+head file.txt               # first 10 lines
+head -n 20 file.txt         # first 20 lines
+tail file.txt               # last 10 lines
+tail -f logfile.log         # follow log in real time
+
+# Search text
+grep "pattern" file.txt        # search in single file
+grep -r "pattern" /path/dir    # recursive in directory
+grep -ri "pattern" /path/dir   # recursive and case-insensitive
+```
+
+---
+
+## 4. Permissions & Ownership
+
+```bash
+# View permissions and ownership
+ls -l /path/to/file_or_dir
+
+# Change permissions
+chmod 644 file.txt          # owner read/write, group/others read
+chmod 600 secret.txt        # owner read/write only
+chmod +x script.sh          # add execute bit
+
+# Change owner and group
+chown user:group file.txt
+chown -R user:group /path/to/dir   # recursive
+```
+
+---
+
+## 5. Users, Groups & sudo (Debian/Ubuntu style)
+
+```bash
+# Identify current user and groups
+whoami
+id                          # show UID, GID, and groups
+
+# Run a command as root (if allowed)
+sudo command                # run single command with privileges
+
+# User management (Debian/Ubuntu)
+sudo adduser newuser        # interactive user creation
+sudo passwd newuser         # set or change password
+
+# Add user to an additional group
+sudo usermod -aG sudo newuser      # grant sudo rights (example)
+sudo usermod -aG docker newuser    # allow use of docker group
+```
+
+---
+
+## 6. Processes & System Monitoring
+
+```bash
+# List processes
+ps aux                      # all processes with details
+
+# Real-time monitoring
+top                         # built-in monitor
+htop                        # improved top (if installed)
+
+# Kill a process by PID
+kill 1234                   # ask process to terminate
+kill -9 1234                # force kill (SIGKILL)
+
+# Jobs in current shell
+jobs                        # list background jobs
+fg %1                       # bring job 1 to foreground
+bg %1                       # send job 1 to background
+```
+
+---
+
+## 7. Services & Logs (systemd)
+
+```bash
+# Service management (systemd)
+sudo systemctl status nginx.service     # check status
+sudo systemctl start nginx.service      # start service
+sudo systemctl stop nginx.service       # stop service
+sudo systemctl restart nginx.service    # restart service
+sudo systemctl enable nginx.service     # start at boot
+sudo systemctl disable nginx.service    # do not start at boot
+
+# View logs with journalctl
+sudo journalctl -u nginx.service        # logs for one unit
+sudo journalctl -u nginx.service -f     # follow logs
+sudo journalctl -b                      # logs from current boot
+```
+
+---
+
+## 8. System Information & Resources
+
+```bash
+# Basic system info
+uname -a                    # kernel and system info
+hostname                    # system hostname
+
+# Disk and filesystem usage
+df -h                       # disk usage by filesystem
+du -sh /path/to/dir         # summary size of a directory
+
+# Memory and swap usage
+free -h
+
+# Uptime and logged-in users
+uptime
+w                           # who is logged in and what they do
+```
+
+---
+
+## 9. Networking Basics
+
+```bash
+# IP addresses and links
+ip a                        # show interfaces and addresses
+ip r                        # routing table
+
+# Connectivity tests
+ping 8.8.8.8                # test raw connectivity
+ping example.com            # test DNS + connectivity
+
+# Open/listening ports
+sudo ss -tulpn              # TCP/UDP sockets with PIDs
+
+# HTTP requests and downloads
+curl https://example.com    # simple HTTP GET
+wget https://example.com/file.iso   # download file
+```
+
+---
+
+## 10. Storage & Mounts (Conceptual Commands)
+
+```bash
+# List block devices (disks/partitions)
+lsblk                       # tree view of devices and mount points
+
+# Show filesystems and usage
+df -h                       # mounted filesystems
+
+# Show current mounts
+mount | grep "/"
+
+# View /etc/fstab (persistent mounts)
+sudo nano /etc/fstab        # edit with care
+```
+
+---
+
+## 11. Archives & Compression
+
+```bash
+# Create and extract tar archives
+tar -cf archive.tar file1 dir2          # create tar
+tar -xf archive.tar                     # extract tar
+
+# Create and extract compressed tar.gz
+tar -czf archive.tar.gz file1 dir2      # create tar.gz
+tar -xzf archive.tar.gz                 # extract tar.gz
+
+# Zip archives
+zip archive.zip file1 file2             # create zip
+unzip archive.zip                       # extract zip
+```
+
+---
+
+## 12. Package Management (Debian / Ubuntu)
+
+```bash
+# Update package lists and upgrade
+sudo apt update                         # refresh package index
+sudo apt upgrade                        # upgrade installed packages
+
+# Install, remove, purge packages
+sudo apt install htop                   # install package
+sudo apt remove htop                    # remove package (keep config)
+sudo apt purge htop                     # remove package + config
+
+# Search and inspect packages
+apt search nginx                        # search in repositories
+apt show nginx                          # show details
+```
+
+---
+
+## 13. SSH & Remote Access
+
+```bash
+# Connect to a remote host
+ssh user@server.example.com
+
+# Use a specific key and port
+ssh -i ~/.ssh/id_ed25519 -p 2222 user@server.example.com
+
+# Copy files over SSH
+scp file.txt user@server.example.com:/remote/path/
+scp -r dir/ user@server.example.com:/remote/path/
+```
+
+---
+
+## 14. Shutdown & Reboot
+
+```bash
+# Shutdown and reboot (systemd)
+sudo shutdown now                      # immediate shutdown
+sudo shutdown -r now                   # immediate reboot
+sudo shutdown +5                       # shutdown in 5 minutes
+
+sudo reboot                            # reboot system
+sudo poweroff                          # power off system
+
+sudo systemctl reboot                  # reboot via systemd
+sudo systemctl poweroff                # power off via systemd
+```
+
+---
+
+## 15. Shell Shortcuts (Bash)
+
+- `Ctrl + C` – Cancel current command
+- `Ctrl + D` – Logout / send EOF
+- `Ctrl + R` – Search in command history
+- `↑` / `↓` – Navigate command history
+- `Tab` – Auto-completion