tmux — Terminal multiplexer (alternative to screen) for running/previewing multiple processes and persisting sessions across disconnects. Has 3 layers: session, window, panes.

• Shortcuts (prefix CTRL + b):
  • d – detach from session
  • SHIFT + 5 – horizontal pane split
  • SHIFT + ' – vertical pane split
  • Arrow keys – switch panes
  • q – show pane index numbers (q + 2 to jump to pane 2)
  • CTRL + Arrow keys (hold) – resize pane
  • ALT (1-2) – layout options
  • c – new window
  • n – next window
  • , – rename window
  • w – list windows/sessions
  • x – kill pane
  • SHIFT + 7 – kill window
  • [ – scroll/navigate pane (g + line number to jump)
• Commands:
  • tmux a – attach to most recent session
  • tmux new -s <session name> – create named session
  • tmux ls – list sessions
  • tmux a -t <session_name> – attach to specific session
  • tmux kill-session [-t <session_name>] – kill session
  • tmux kill-server – kill all sessions
• Tip: add setw -g mode-keys vi to ~/.tmux.conf for vi keybindings (space to highlight, enter to copy, CTRL+b+] to paste)

GlusterFS — Open-source distributed filesystem for scalable storage across multiple servers/nodes, allowing shared storage across e.g. multiple Kubernetes nodes.

• Note: Gluster-specific commands (e.g. gluster volume create) run on one server propagate to the whole cluster.
• References: Digital Ocean's article, GlusterFS install/config docs (latest version 11), volume types docs.
• Setup summary:
  • Servers: install glusterfs-server from PPA, create mount dir, start/enable glusterd, add hosts entries, gluster peer probe, gluster peer status, gluster volume create ... replica ... force, gluster volume start, status, info, profile start/info
  • Clients: install glusterfs-client, create mount path, mount -t glusterfs ..., verify with df -kh, add entry to /etc/fstab

rsnapshot — Open-source incremental backup utility based on rsync; supports local and remote (SSH) machines.

• Does not run automatically — execute rsnapshot <level_name> via script or cron
• Level names (e.g. alpha, hourly) must be unique and in ascending order; each level creates numbered directories (e.g. alpha.0 newest to alpha.5 oldest)
• snapshot_root /path/to/directory sets where backups are stored
• backup directives map source paths to snapshot subdirectories
• For SSH: uncomment cmd_ssh, and optionally cmd_du and link_dest

BIND DNS — Open-source DNS server suite for resolving domain names/IPs, supporting authoritative DNS, caching, zone management, etc.

• By default performs recursion (fetches DNS data from other servers if not cached locally)
• named.conf — main config file; supports include and ACLs
  • Example includes directory, recursion yes, allow-query, forwarders, and zone blocks
• Zone files (e.g. /var/named/example.com.zone) define authoritative records: SOA, NS, A, AAAA, CNAME, MX, TXT, etc.
• Restart with sudo systemctl restart named.service after changes; test with nslookup or dig
• Reference: Digital Ocean's in-depth guide

GPG (File Encryption) — GnuPG, an open-source OpenPGP implementation for encrypting/decrypting files and securing communications.

• Keys stored in .gnupg directory (pubring.kbx for public, secring.kbx for secret)
• Common commands:
  • gpg --full-generate-key – generate key
  • gpg --list-keys / gpg --list-secret-keys – list keys
  • gpg --export --armor <ID/email> > publickey.asc – export public key
  • gpg --import <file> – import a public key
  • gpg --encrypt --recipient <email> <file> – encrypt
  • gpg --decrypt <file.gpg> > <file> (or d) – decrypt
• Other encryption options:
  • zip --encrypt secure.zip <files> – password-protected zip
  • openssl pkeyutl – alternative for smaller files:
    • Generate private key: openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:4096 -outform pem -out rsakey.pem
    • Generate public key: openssl pkey -in rsakey.pem -out rsapubkey.pem -outform pem -pubout
    • Encrypt: openssl pkeyutl -encrypt -pubin -inkey rsapubkey.pem -in <file> -out <file.enc>
    • Decrypt: openssl pkeyutl -decrypt -inkey rsakey.pem -in <file.enc> -out <file>

WoeUSB — Simplifies creating a bootable Windows USB installer

• sudo woeusb --device /path/to/Win10_22H2_English_x64v1.iso /dev/sdX

Tracee — Open-source runtime security/forensics tool for Linux by AquaSec, using eBPF to detect suspicious behavior, anomalies, and malicious activity in real time

• Can detect privilege escalation, fileless malware, suspicious syscalls, unusual network activity, etc.
• Use cases: runtime threat detection, incident forensics, container security, compliance monitoring, DevSecOps pipeline integration
• Requires eBPF support; builds eBPF program stored at /tmp/Tracee by default
• Can be used in Docker or Kubernetes
• Reference: https://aquasecurity.github.io/tracee/latest/docs/install/docker/

WinApps — Lets Linux users run Windows apps (e.g. MS Office, Photoshop) natively-integrated on the Linux desktop

• Runs Windows in a VM (KVM, Docker, or libvirt), connects via RDP, renders apps with FreeRDP alongside Linux apps
• Reference: https://github.com/winapps-org/winapps

Waydroid — Open-source, container-based compatibility layer to run a full Android system (LineageOS-based, Android 11/13) on Linux

• Uses kernel namespaces (user, pid, uts, net, mount, ipc) instead of virtualization for near-native performance
• Useful for authenticators, banking apps, messaging tools
• Reference: https://github.com/waydroid/waydroid

ntopng — Network traffic probe providing 360° network visibility

• Gathers data from traffic mirrors, NetFlow exporters, SNMP devices, firewall logs, IDS
• Unlike a plain traffic collector, it also analyzes traffic, identifies traffic types, and reports cybersecurity metrics

PFSense — Open-source customized FreeBSD distribution built for use as a firewall/router, fully managed via a web interface