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🐧 Linux Command Cheat Sheet

Miscellaneous & Essential Snippets

A collection of "how-to" commands and tools for quick reference.

🏗️ System & Hardware Information

Command Description
lscpu Detailed information about the CPU architecture.
lshw List all hardware. Use lshw -C display for GPU info.
lsblk List block devices (view partitions/mount points).
blkid Get UUIDs for drives/volumes (essential for /etc/fstab).
free -m Show RAM usage in Megabytes.
screenfetch Display system info with an ASCII logo.
hwclock --systohc Sync hardware clock to system time.

💾 Storage & Disk Management

Drive Identification

  • Find Serial Numbers: udevadm info --query=all --name=/dev/sda | grep ID_SCSI_SERIAL
  • Identify physical slot position: lsscsi
  • Identify disk via LED (if supported): ledctl locate=/dev/sda

Disk Health & Performance

  • Check SMART status: smartctl -a /dev/sda
  • Grab Disk Temp: smartctl -a -d sat /dev/sda | grep Temp | awk -F " " '{print $10}'
  • IOPS Monitoring: iostat -y 1 1 (Current stats, requires sysstat) iotop -botqqq -u [user] --iter=5 (Process-specific I/O)

File Systems

  • Allocate sparse file: fallocate -l 10G test_file
  • BTRFS Management:
    • btrfs device add -f /dev/sdb /media/usb1/ (Add device)
    • btrfs balance start -dconvert=raid1 -mconvert=raid1 /media/usb1/ (Mirror/Balance)
    • btrfs filesystem defragment /media/usb1/ (Defrag)
    • btrfs scrub start /mounted/path (Check integrity)
    • btrfs subvolume snapshot /src /dest/snapshot-name (Snapshot)

🌐 Networking

Monitoring & Usage

  • Bandwidth (ASCII): nload or speedometer -r eth0 -t eth0
  • Interface Top: iftop
  • Deep Dive TUI: iptraf
  • Traffic Stats over time: vnstat
  • Public IP: wget http://ipinfo.io/ip -qO -
  • Netstat (Listening ports): netstat -tulpn

Utils & Config

  • Clean ARP List: arp -a | grep -v incomplete | awk -F " " '{printf $2 " " $4 "\n"}' | tr '()' ' '
  • Manage Resolv: resolvconf -a eth0
  • Tunneling: autossh -o GatewayPorts=true -R 0.0.0.0:8889:127.0.0.1:8889 remotehost -p [port] -l [user] -g -v -N

📊 System Monitoring & Processes

"Top" Variants

  • Glances: Comprehensive system overview (glances)
  • Atop: Advanced system & process monitor (atop)
  • Ntop: Network traffic probe (ntop)
  • Htop: Interactive process viewer (htop)

Process Management

  • Watch command output: watch -n 15 [command]
  • Persistent process (no-hangup): nohup [command] &
  • Identify/Kill remote login session: ps -t pts/5 | awk -F ' ' '{print $1}' | tail -1 | xargs kill -9
  • Whowatch: Real-time user/process monitoring.

📝 Logs & Text Processing

Log Utilities

  • Colorize logs: ccze -A < /var/log/syslog
  • Multi-log viewer: multitail
  • Add timestamps to pipes: [command] | ts (requires moreutils)
  • HTML Converter: aha (converts ANSI color to HTML)

Text Snippets

  • Extract Emails: cat file.txt | awk -F " " '{for(i=1; i<=NF; i++)if($i ~ /@/) print $i }'
  • Count words/lines: wc
  • Named Pipes: mkfifo pipe2; ls > pipe2 (then cat < pipe2 in another terminal)

🛠️ Package Management & Security (Debian/Ubuntu)

  • Purge App (incl. configs): apt-get purge [package]
  • Unattended Upgrades: dpkg-reconfigure unattended-upgrades
  • Security: fail2ban
  • Hide processes from other users: mount -o remount,rw,hidepid=1 /proc
  • Process Accounting: psacct (or acct)

🗃️ Specific Tools

  • BackupPC Restore Snippet: /usr/share/backuppc/bin/BackupPC_tarCreate -h hostname -n -1 -s /home/user /file.txt > backup.tar
  • Proxmox Time Sync (Chrony): echo server '192.168.1.1 iburst' > /etc/chrony/sources.d/local.sources
  • CLI Fun:
    • curl wttr.in/dublin (Weather)
    • glow (Markdown renderer)
    • chafa (Images to ANSI)
    • mc (Midnight Commander)

⌨️ Bash / Readline Shortcuts

Shortcut Action
ALT + B / F Move cursor back/forward by one word.
CTRL + U Delete text from cursor to start of line.
CTRL + K Delete text from cursor to end of line.
ALT + U / L Uppercase / Lowercase word forward.
CTRL + X + X Toggle cursor between current position and start of line.