Mac
Mac runbooks for macOS Tahoe
Operator-grade troubleshooting for the Mac as home infrastructure on macOS Tahoe (macOS 26): Time Machine to a NAS, Mac mini home servers, storage and System Data, displays and docks, Wi-Fi, and boot. Every page is source-backed, pinned to the exact macOS point release, and written to leave you with a fix — not a list of vague tips.
Backups & Time Machine
Getting a real, restorable backup off a Mac — Time Machine to a NAS over SMB, sparsebundle repair, the 3-2-1 plan, and the iCloud storage trap.
Why Time Machine over SMB to a Synology, QNAP, TrueNAS, or Unraid NAS fails on macOS Tahoe (macOS 26), and the exact fixes — including the two separate Tahoe bugs most guides miss.
Open runbookFix a Time Machine network backup that says the sparsebundle is in use, couldn't be accessed, or is damaged — attach it with hdiutil, run fsck_apfs / First Aid, clear stale locks, re-claim it with tmutil, and know when to rebuild.
Open runbookHow to build a real 3-2-1 backup for a Mac — three copies, two media, one offsite — using Time Machine plus a NAS and a cloud backup, why a bootable clone is no longer the rescue disk on Apple Silicon, and where iCloud fits (and doesn't).
Open runbookWhy 'Optimize Mac Storage' can leave your Time Machine backup full of empty placeholders instead of real files — how iCloud dataless files work, whether Time Machine backs up iCloud, and the safe settings.
Open runbookMac as a home server
Running a Mac mini 24/7 — stopping it from sleeping, Plex/Jellyfin transcoding, headless setup, auto power-on, and power cost.
Stop a Mac mini from sleeping when you run it 24/7 as a Plex, Jellyfin, or file server on macOS Tahoe — the Energy setting most people miss, plus pmset and caffeinate, and why caffeinate alone fails on M4.
Open runbookHow to run a Mac mini headless as a 24/7 home server on macOS Tahoe (macOS 26) — never-sleep, auto-login, launchd vs LaunchAgent for services, headless display (dummy plug vs High Performance screen sharing), and the FileVault trade-off.
Open runbookHow to get a Mac mini to power back on by itself after a power cut on macOS Tahoe (macOS 26) — the new 26.5 Energy setting, pmset autorestart, auto-login so services return, and the FileVault catch-22 that blocks unattended restart.
Open runbookWhy an M4 Mac mini handles far more Plex/Jellyfin transcodes than the 'Apple Silicon only does one stream' myth claims — VideoToolbox, why native beats Docker, hardware HDR tone mapping, and the AV1 decode-only caveat.
Open runbookPerformance & system
A Mac that got slow after the Tahoe update — the memory leak, high-CPU processes (kernel_task, WindowServer, Spotlight), and beachballs.
Why your Mac feels slow, laggy, or runs out of memory after updating to macOS Tahoe (macOS 26) — the two confirmed Tahoe bugs with exact fixes, plus the normal post-update slowdown that clears on its own.
Open runbookFix "Your system has run out of application memory" on macOS Tahoe (macOS 26) — the autofill bug, the Electron app memory leak, and how to tell when you actually need more RAM, using the built-in Memory Pressure graph.
Open runbookStorage & disk space
Reclaiming space when 'System Data' or purgeable space balloons — APFS local snapshots, caches, and what's actually safe to delete.
Why deleting files doesn't free space on a Mac and 'System Data' or 'purgeable' stays huge — APFS local Time Machine snapshots, and how to list and thin them with tmutil without breaking your backups.
Open runbookWhat the 'System Data' (or 'Other') storage category on a Mac actually contains — snapshots, caches, Mail, Messages, iOS backups, Xcode, Docker — and how to find and reclaim it natively, without a cleaner app.
Open runbookDisplays & docks
External monitors and docks on Apple Silicon — displays not detected after an update, per-chip display limits, DisplayLink, and mirror-vs-extend.
Why an external monitor stopped working after a macOS Tahoe (macOS 26) update — power-cycle the dock, force Detect Displays, swap the cable, bypass the dock, and the 26.4/26.4.1 display regression to know about.
Open runbookHow many external monitors each Apple Silicon chip supports (M1–M5, Pro, Max, Ultra) — the per-chip limits, why a dock can't add more, the base-M3 clamshell exception, and when you need DisplayLink.
Open runbookWhy two monitors on a Mac dock show the same screen instead of extending — the quick mirror setting to uncheck, and the real reason on Apple Silicon: macOS doesn't support DisplayPort MST, so a one-port dock can only mirror.
Open runbookWi-Fi & networking
Mac networking — Wi-Fi that keeps dropping, 'connected but no internet', the Local Network permission that hides your NAS and printer, and Private Wi-Fi Address.
Why a Mac's Wi-Fi keeps disconnecting or drops after updating to macOS Tahoe (macOS 26) — read diagnostics with wdutil, reset the network config, fix the WPA2/WPA3 and band-steering router settings behind it, and the 26.4.1 fix.
Open runbookFix a Mac that shows full Wi-Fi but won't load anything — isolate DNS vs routing with ping, flush DNS, renew DHCP, handle IPv6 and captive portals, and the wrong-clock TLS trap that blocks HTTPS.
Open runbookWhy your Mac stopped seeing the NAS, shared folders, or printer after updating to macOS Tahoe (macOS 26) — the Local Network privacy permission that resets on update, Bonjour/mDNS discovery, and the VPN that hides the LAN.
Open runbookBoot & security
When a Mac won't start — boot loops, stuck-at-login, the 'app is damaged' Gatekeeper message, and FileVault recovery.
What to do when an Apple Silicon Mac won't start, restarts in a loop, or hangs on the Apple logo — enter Recovery by holding the power button, use Safe Mode, and reinstall without erasing (the mistake that wipes your data).
Open runbookFix "<app> is damaged and can't be opened" or "can't be opened because Apple cannot check it for malicious software" on macOS — the safe Open Anyway path, the quarantine fix for trusted apps, and the override never to use.
Open runbook20 Mac runbooks and growing. New macOS Tahoe operator pages are added as each theme is built out.