Resources Library
Cheat sheets, reference guides and useful bits of Linux and Unix knowledge. No gatekeeping. Occasional cryptic commands.
We're building a growing library of Linux and Unix technical references, practical examples and downloadable guides. Some sections are still being developed. Please bear with us!
📁 Library
📁 Editors
Text editors and their command languages.
📁 vi & Vim
Reference guides and cheat sheets for the vi family of editors.
📄 History of vi — timeline PDF ↗ 📄 Normal-mode command reference PDF ↗ 📄 Pocket quick reference PDF ↗ 📄 Vi Vim Command Crib Sheet PDF ↗📁 Logging
📁 logrotate
Rotating, compressing and retaining text logs
📄 logrotate quick reference /etc/logrotate.conf defines global defaults; /etc/logrotate.d/ contains per-service rules. HTML ↗ 📄 Logrotate Reference PDF ↗📁 rsyslog
Syslog routing, selectors and journal interaction
📄 rsyslog quick reference rsyslog receives messages and routes them according to rules. Facilities describe sources; severities describe prio HTML ↗ 📄 Rsyslog Reference PDF ↗📁 Security
📁 SSH security
Keys, configuration, validation and operational safety
📄 OpenSSH hardening checklist Keep a working session open and ensure console access before editing remote SSH configuration. HTML ↗ 📄 Ssh Key Authentication PDF ↗ 📄 SSH public-key authentication The private key remains on the client. The server stores the public key in authorized_keys. During authentication t HTML ↗ 📄 Sshd Hardening PDF ↗📁 TOTP for SSH and sudo
PAM-based one-time passwords with standard authenticator apps
📄 TOTP concepts and limitations The server and phone share a secret established at enrolment. Both calculate short-lived codes from the secret and HTML ↗ 📄 PAM TOTP deployment checklist Test in a disposable VM, snapshot it, keep a root console and an existing SSH session. Back up PAM and SSH configur HTML ↗📁 TOTP and two-factor authentication
Time-based one-time passwords for SSH and sudo.
📄 How TOTP works An authenticator and server share a secret. Both calculate a short-lived code from that secret and the current time. Correct PDF ↗ 📄 TOTP with OpenSSH A common implementation uses libpam-google-authenticator; the name describes the PAM module, not a requirement to use Google’ PDF ↗ 📄 TOTP with sudo The sudo PAM service can require a TOTP prompt using pam_google_authenticator.so. It is separate from the SSH PAM service. PDF ↗📁 Shell
📁 Bash TAB completion
Interactive completion and the programmable-completion interface
📄 Bash Tab Completion PDF ↗ 📄 Bash completion essentials TAB completes commands, paths and other words. A second TAB may list alternatives depending on Readline configurati HTML ↗ 📄 Six completion variables COMP_WORDS is an array of parsed words. COMP_CWORD indexes the current word (zero-based). HTML ↗📁 Storage
📁 Logical Volume Manager
LVM fundamentals, RAID, thin provisioning and snapshots
📄 LVM fundamentals A physical volume (PV) is a disk or partition initialised for LVM. A volume group (VG) pools PV capacity. A logical HTML ↗ 📄 Lvm Fundamentals PDF ↗ 📄 LVM RAID reference RAID can maintain availability after certain disk failures; it cannot replace independent, tested backups. HTML ↗ 📄 Lvm Raid PDF ↗ 📄 LVM snapshots A snapshot captures a point-in-time view of a logical volume. It is not a backup unless exported and stored indepen HTML ↗ 📄 Lvm Snapshots PDF ↗ 📄 LVM thin provisioning A thin pool stores shared physical extents; thin volumes advertise virtual capacity that may exceed currently alloc HTML ↗ 📄 Lvm Thin PDF ↗