أوامر Linux الأساسية لـ DevOps (الجزء الأول)

# Old way: ls (lists directory contents)
ls -la                    # List all files, detailed format

# Modern replacement: eza (faster, colored, Git-aware)
eza -la                   # Same output, with better colors
eza -la --tree            # Directory tree view
eza -la --git             # Shows Git status alongside files

pwd                       # Print working directory (where are you?)
cd /path/to/dir           # Change directory
cd ~                      # Go to home directory
cd -                      # Go to previous directory
cd ..                     # Go to parent directory
cd ../..                  # Go up two levels

# Old way: cat
cat /var/log/syslog       # Print entire file to terminal (Debian/Ubuntu)
cat /var/log/messages     # Same, on RHEL/CentOS/Fedora-based systems

# Better alternatives:
bat /var/log/syslog       # Syntax highlighting + line numbers
bat -p /var/log/syslog    # Plain mode (no decorations: no header, grid, or line numbers)
tail -f /var/log/syslog   # Follow log file in real-time
head -20 /var/log/syslog  # First 20 lines only

touch filename                  # Create empty file or update timestamp
mkdir -p /path/to/dir          # Create directory (and parent dirs if needed)
rm filename                     # Delete file (DANGER: permanent!)
rm -r dirname                   # Delete directory and contents
rmdir dirname                   # Remove empty directory only

cp source.txt destination.txt   # Copy file
cp -r source_dir dest_dir       # Copy directory recursively
mv old_name new_name            # Move or rename
mv -i old_name new_name         # Interactive (asks before overwriting)

# Old way: find
find /path -name "*.log"        # Find all .log files
find /path -type f -size +100M  # Find files larger than 100MB

# Modern replacement: fd (faster, colored, regex by default)
fd -e log /path                # Find .log files (extension match, idiomatic fd)
fd "\.log$" /path              # Same, using regex
fd --size +100M /path          # Files larger than 100 megabytes
fd --follow                    # Follow symlinks

chmod 755 script.sh             # Owner: rwx, Group: r-x, Others: r-x
chmod 644 config.yaml           # Owner: rw-, Group: r--, Others: r--
chmod u+x script.sh             # Add execute permission for owner
chown user:group filename       # Change owner and group
chown -R user:group dirname     # Recursive ownership change

# Old way: grep
grep "error" /var/log/app.log   # Find lines containing "error"
grep -r "TODO" .                # Recursively search all files
grep -i "Error" file.txt        # Case-insensitive search

# Modern replacement: ripgrep (rg)
rg "error" /var/log/            # Faster recursive search
rg -g "*.yaml" "apiVersion"     # Search only in YAML files
rg --type rust "TODO"           # Search only in Rust files

systemctl status nginx                    # Check if nginx is running
systemctl start nginx                     # Start service
systemctl stop nginx                      # Stop service
systemctl restart nginx                   # Restart service
systemctl enable nginx                    # Auto-start on boot
systemctl disable nginx                   # Don't auto-start on boot
systemctl list-units --type=service       # List all services
journalctl -u nginx                       # Logs for nginx service only
journalctl -u nginx -f                    # Follow nginx logs
journalctl -u nginx --since "10 minutes ago"  # Recent logs
journalctl -n 50 -u nginx                 # Last 50 lines

# List all namespaces on system
lsns

# Inspect cgroups (Linux container boundaries)
cat /proc/cgroups               # Lists registered cgroup controllers (cgroup v1 view)
cat /sys/fs/cgroup/cgroup.controllers  # Available controllers (cgroup v2; default on most modern distros)
ps aux | grep <container-id>    # Find processes belonging to a container

# Mount inspection (important for volume debugging)
mount | grep -i docker          # Show Docker-related mounts
df -h                           # Disk usage by mount point

# On Windows PowerShell:
wsl --install                   # Install WSL2
wsl --list --verbose            # List installed distributions
wsl -d Ubuntu                   # Run specific distribution

# From within WSL2:
/mnt/c/                         # Access Windows C: drive
/mnt/d/                         # Access Windows D: drive