Linux cheat sheets
These five sheets cover the Linux a sysadmin actually types. Essential commands is the daily driver: navigation, reading logs, grep and text reshaping, tar, processes and packages. systemd services pairs every systemctl verb with the journalctl query that explains what the service did. Networking is built entirely on the modern iproute2 stack — ip and ss — plus dig, curl, NetworkManager and both firewall families.
The remaining two finish the picture: disks & storage runs from df -h triage through fstab and SMART to a compact LVM reference, and permissions & ownership decodes numeric chmod, umask, the special bits and ACLs with honest security notes. Everything assumes a current mainstream distro — Debian 12+, Ubuntu 22.04+, RHEL 9 / Rocky / Alma / Fedora — with systemd 250+, GNU coreutils and iproute2. Where Debian-family and Red Hat-family differ (packages, firewalls), the row says which is which.
Cheat sheets
Essential commands
Navigate, read, search, archive and manage processes — the 40-plus commands behind every Linux session
systemd services
systemctl control verbs, unit overrides and journalctl log queries — including masking, editing and journal disk limits
Networking
ip and ss from iproute2, dig and curl, NetworkManager profiles, hostnamectl, plus ufw and firewalld one-liners
Disks & storage
df and du capacity triage, lsblk and mounting, fstab done safely, SMART health, TRIM, careful dd and a compact LVM path
Permissions
Numeric and symbolic chmod decoded, chown patterns, umask math, SUID/SGID/sticky with security notes, and setfacl ACLs
Free network tools
Subnet CalculatorIPv6 CalculatorWildcard MaskRange → CIDRSplitterAggregatorVLSM CalculatorPracticeCheat Sheet
FAQ
Which Linux distributions do these cheat sheets assume?
Current mainstream releases: Debian 12+, Ubuntu 22.04/24.04, Fedora, and the RHEL 9 family (RHEL, Rocky, Alma). Everything assumes systemd 250+, GNU coreutils, util-linux and iproute2 — the stack those distros ship. The genuine divergence points are called out inline: package management (apt vs dnf) and firewalls (ufw vs firewalld) carry per-family rows.
What replaced netstat and ifconfig on Linux?
iproute2: ss replaces netstat (ss -tulpn is the listening-ports-with-processes audit) and ip replaces ifconfig (ip addr), route (ip route show) and arp (ip neigh). The legacy net-tools binaries are unmaintained, miss modern kernel features and are no longer preinstalled on mainstream distros. The networking sheet includes a full translation table.
Do I need root (sudo) for these commands?
Inventory reads generally do not: ls, cat, grep, ps, df, du, ip addr, ss, systemctl status, journalctl (if you are in the systemd-journal/adm/wheel group), stat and getfacl all run as a normal user. State changes do: installing packages, systemctl start/stop/enable/mask, ip address changes, mount, dd, chmod/chown on files you do not own, firewall rules and fstrim. Rows needing root carry sudo in the sheet itself.
I am new to Linux administration — which sheet first?
Start with the essential commands sheet until navigation, grep and process handling are reflexes, then move to systemd services — managing units and reading journals is the daily rhythm of a Linux admin. Networking and disks slot in as your responsibilities grow, and the permissions sheet doubles as a reference you revisit whenever an access question appears. Each sheet is self-contained and cross-linked.