Cheat Sheets

DNS record types

A, AAAA, CNAME, MX, TXT, NS and others used in infrastructure.

Subnet mask

CIDR notation, usable hosts and common IPv4 subnet ranges.

Common network ports

TCP/UDP ports for SSH, DNS, HTTP, RDP, SMTP and more.

Windows network troubleshooting

ipconfig, netstat, Test-NetConnection, route and netsh, arranged by symptom.

PowerShell commands

Useful PowerShell commands for Windows admin and automation.

Windows Command Line (CMD)

Useful Windows Command Line (CMD) commands.

Windows power user shortcuts

Run commands, .msc snap-ins, shell shortcuts and keyboard shortcuts.

Windows Event ID

Logon, lockout, service and disk events, with Get-WinEvent and wevtutil syntax.

Robocopy

Switches, filters, retry settings and the full exit code table.

NTFS permissions and icacls

Rights codes, inheritance flags, icacls and takeown, and which entry wins.

Windows disk and storage

diskpart, chkdsk online scan, fsutil, vssadmin and the storage cmdlets.

Windows scheduled tasks

schtasks syntax, result codes and why a script fails only when scheduled.

Active Directory troubleshooting

nltest, dcdiag, repadmin, w32tm, klist and setspn, with the error codes.

Group Policy troubleshooting

gpresult, precedence, filtering traps and the events that explain a failure.

Git and GitHub for sysadmins

Version control for scripts and configs: undo, history and safe rollback.

Linux commands

Which command or tool for which job, plus pipes, redirection and quoting.

Linux for Windows admins

Command translation, file layout and what differs between distributions.

vi and vim

Modes, moving, selecting, delete and copy, search and replace, and how to get out.

Linux permissions

chmod values, symbolic notation and common permission patterns.

systemd and journalctl

systemctl, journal filters, unit files, services and timers.

SSH and OpenSSH

Keys, client config, scp and rsync, tunnels and sshd hardening.

Linux networking

ip and ss, DNS, persistent config per distribution, firewalld and ufw.

HTTP status codes

200, 301, 400, 403, 404 and 500 with practical meanings.

VMware PowerCLI

Connect, inventory, VM power, snapshots, hosts and datastores from PowerShell.

VMware ESXi command line

esxcli and vim-cmd for host, network, storage, VM and patching operations.

OpenSSL

Keys, CSRs, certificate inspection, format conversion and live server checks.