⏱️ Boot Time Diagnostics

Use this page when the installed workstation feels slow, especially during boot. Run these commands on the installed machine.

📊 Analyzing Total Boot Time

Start with the total boot summary:

systemd-analyze

Expected result: systemd prints firmware, bootloader, kernel, initrd, and userspace timing. (Note: Manual LUKS passphrase entry pauses the boot process and will inflate the total time. This is not an OS tuning problem and should be judged separately).

🐢 Finding Slow Services

Find the slowest individual units:

systemd-analyze blame

Expected result: The slowest systemd units are listed first. Long-running services become visible without guessing.

⛓️ Inspecting the Critical Path

A service might take a long time to start, but if it runs in parallel with others, it might not actually delay the boot. Inspect the critical path to find what actually blocked the system from reaching the login prompt:

systemd-analyze critical-chain

Expected result: The dependency chain that delayed the boot is visible.

⚠️ Checking Boot Warnings

Check warnings specifically from the current boot:

journalctl -b -p warning

Expected result: Current boot warnings are listed. Repeated hardware, filesystem, network, or graphics warnings can explain slow boot or session startup.

🩺 Common Quick Checks

Symptom	Command	What to look for
Network delays	systemctl status NetworkManager	NetworkManager should be active; boot should not wait for online networking.
Slow graphical login	systemctl status display-manager	SDDM should be active and not repeatedly restarting.
DNS issues after boot	resolvectl status	DNS servers and DNS-over-TLS state should be visible.
Time sync issues	timedatectl status	System clock and NTP state should be sane.

Do not tune the system blindly based on these commands. Collect the output first, then change the smallest specific setting that explains the measured problem in your NixOS configuration.