Frank
02883d3ed2
Copy of the legacy ~/.pi/agent/docs tree rebuilt as the command-center knowledge base: concept files promoted to path identity, index listings stripped of frontmatter, all wikilinks/relative links resolved, every checkable claim verified against the live fleet (Dankserver = Ryzen 7 7700X + RTX 3090; Strix Halo is Dankclaw), unverifiable claims tagged. kb-lint exits 0.
302 lines
6.5 KiB
Markdown
302 lines
6.5 KiB
Markdown
---
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type: reference
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title: Linux Power Management
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description: Sleep/wake troubleshooting, NVIDIA GPU power management, and diagnostics for Linux systems.
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tags:
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- power-management
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- sleep
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- nvidia
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timestamp: 2026-08-06
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---
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Comprehensive guide to sleep/wake configuration and diagnostics on Linux systems. Covers systemd sleep, kernel states, NVIDIA GPU power management, and diagnostic tools.
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---
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## Systemd Sleep Configuration
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### logind.conf (`/etc/systemd/logind.conf`)
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Controls login manager behavior around sleep:
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```ini
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[Login]
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HandlePowerKey=poweroff
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HandleSleepKey=suspend
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HandleHibernateKey=hibernate
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HandleLidSwitch=suspend
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HandleLidSwitchDocked=ignore
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HoldoffTimeoutSec=5s
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IdleAction=hibernate
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IdleActionSec=30min
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```
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**Key setting**: `HoldoffTimeoutSec` — increase if sleep triggers are too aggressive.
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### sleep.conf (`/etc/systemd/sleep.conf`)
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Controls the actual sleep behavior:
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```ini
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[Sleep]
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AllowSuspend=yes
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AllowHibernation=yes
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AllowHybridSleep=yes
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HibernateMode=platform+shutdown
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HibernateDelaySec=1800
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```
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**HibernateMode options**:
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- `platform` — ACPI platform sleep (faster, firmware-dependent)
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- `shutdown` — classic shutdown-to-disk (slower, more compatible)
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- `shutdown+platform` — try platform first, fall back to shutdown
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### Suspend-Then-Hibernate Flow
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```
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Suspend (RAM) --timeout--> Hibernate (disk)
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+-- wake event --> Resume
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```
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### Custom Sleep Hooks
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Create `/etc/systemd/system-sleep/` scripts for pre/post sleep actions:
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```bash
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#!/bin/bash
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# /etc/systemd/system-sleep/hook
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case "$1" in
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pre) echo "Suspending..." ;;
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post) echo "Resumed!" ;;
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esac
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```
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---
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## Kernel Sleep States
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### ACPI Sleep States
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| State | Name | Power | Wake Time | Description |
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|-------|------|-------|-----------|-------------|
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| S0 | Working | Full | Instant | System is running |
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| S1 | Sleep (halted) | ~10-20W | <1s | CPU halted, RAM refresh |
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| S2 | Sleep | ~5-10W | ~1s | CPU cache flushed |
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| **S3** | **Sleeping Standby** | **~1-5W** | **~1-2s** | **RAM retained, most power off** |
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| S4 | Hibernate | 0W | ~10-30s | RAM written to disk |
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| **S5** | **Soft Off** | **0W** | **~5-10s** | **Powered off but can wake** |
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### Modern ACPI Sleep States (s2idle)
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Modern laptops often **only support s2idle** (S0 idle):
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```bash
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$ cat /sys/power/mem_sleep
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[s2idle] deep
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```
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| Mode | Name | Power | Characteristics |
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|------|------|-------|----------------|
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| **s2idle** | "Suspend to Idle" | 3-8W | Shallow, firmware-managed, fast wake, higher drain |
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| **deep** | S3 | 1-3W | Deeper sleep, slower wake, better battery |
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### Setting Default Sleep State
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Add to kernel command line (GRUB or systemd-boot):
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```
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mem_sleep_default=deep # Prefer S3 deep sleep
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mem_sleep_default=s2idle # Force s2idle
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```
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**For GRUB:** Edit `/etc/default/grub`, add to `GRUB_CMDLINE_LINUX_DEFAULT`:
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```
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GRUB_CMDLINE_LINUX_DEFAULT="... mem_sleep_default=deep"
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```
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---
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## NVIDIA GPU Power Management
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### Enable NVIDIA Suspend Support
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```bash
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sudo systemctl enable nvidia-suspend.service
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sudo systemctl enable nvidia-suspend-then-hibernate.service
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sudo systemctl enable nvidia-hibernate.service
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```
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### NVIDIA Module Parameters
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Edit `/etc/modprobe.d/nvidia.conf`:
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```
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options nvidia NVreg_PreserveVideoMemoryAllocations=1
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options nvidia NVreg_EnableS0ixPowerManagement=1
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```
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### Check NVIDIA GPU State
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```bash
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# Is the NVIDIA GPU active?
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lspci -vnn | grep -A 12 -i "vga"
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# Force NVIDIA GPU to D3hot (fully off) before suspend
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sudo tee /sys/bus/pci/devices/0000:01:00.0/power/control <<< auto
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```
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---
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## Diagnostic Tools
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### journalctl
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```bash
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# All sleep-related events in the last boot
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journalctl -b -0 | grep -iE 'suspend|resume|sleep|wake|acpi'
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# Real-time monitoring during a suspend attempt
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journalctl -f &
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systemctl suspend
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# Wait for failure, then Ctrl+C
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```
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### powertop
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```bash
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sudo powertop # Interactive view
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sudo powertop --calibrate # One-time setup
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sudo powertop --auto-tune # Apply recommendations
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sudo powertop --html=/tmp/report.html --csv=/tmp/report.csv
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```
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### tlp — Advanced Power Management
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```bash
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sudo pacman -S tlp tlp-rdw # Arch
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sudo apt install tlp # Debian/Ubuntu
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sudo systemctl enable --now tlp
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sudo tlp-stat
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```
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### dmesg
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```bash
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dmesg | grep -iE 'suspend|resume|acpi|pm_'
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dmesg -wH # Watch mode, human-readable
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```
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---
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## Wake Source Management
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### Checking Wake Sources
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```bash
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# What can wake the system?
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cat /proc/acpi/wakeup | grep enabled
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# What woke the system last time?
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journalctl -b -1 | grep -iE 'PM: wakeup|wakeup source|acpi: wakeup'
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```
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### Toggling Wake Sources
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```bash
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# Toggle a device's wake capability
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echo XHCI | sudo tee /proc/acpi/wakeup
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echo RP01 | sudo tee /proc/acpi/wakeup
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```
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### Persistent Wake Source Configuration
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Create a systemd service:
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```ini
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# /etc/systemd/system/config-wake-sources.service
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[Unit]
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Description=Configure ACPI wake sources
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Before=sleep.target
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[Service]
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Type=oneshot
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ExecStart=/bin/bash -c 'echo XHCI > /proc/acpi/wakeup'
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RemainAfterExit=yes
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[Install]
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WantedBy=multi-user.target
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```
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---
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## Common Kernel Parameters
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| Parameter | Description |
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|-----------|-------------|
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| `mem_sleep_default=deep` | Prefer S3 deep sleep |
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| `pcie_aspm=force` | Force ASPM (aggressive power saving) |
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| `pcie_aspm.policy=performance` | Disable ASPM (fixes some issues) |
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| `acpi_osi=!` | Hide OS identity from ACPI |
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| `usbcore.autosuspend=-1` | Disable USB autosuspend |
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---
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## Testing Sleep Modes
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```bash
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# Suspend to RAM
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systemctl suspend
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# Hibernate to disk
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systemctl hibernate
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# Suspend then hibernate
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systemctl suspend-then-hibernate
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# Freeze (CPUs idle, RAM on)
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systemctl freeze
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```
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### Automated Stress Test
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```bash
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#!/bin/bash
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for i in $(seq 1 10); do
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echo "=== Cycle $i ==="
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date
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echo mem | sudo tee /sys/power/state 2>/dev/null || systemctl suspend
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echo "Resume $i: SUCCESS"
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sleep 5
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done
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```
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---
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## Quick Reference: Action Items
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```bash
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# 1. Enable NVIDIA suspend support
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sudo systemctl enable nvidia-suspend.service
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sudo systemctl enable nvidia-suspend-then-hibernate.service
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# 2. Add NVIDIA power management module parameter
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echo 'options nvidia NVreg_PreserveVideoMemoryAllocations=1' | sudo tee /etc/modprobe.d/nvidia-preserve.conf
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# 3. Reboot
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sudo reboot
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# 4. Test suspend
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systemctl suspend
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# 5. After resume, check for errors
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dmesg | tail -30
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journalctl -b -0 | grep -iE 'error|fail|nvidia' | tail -20
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```
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---
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## Cross-References
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- The [AGENTS.md Format](../core/agents-md-format.md) defines the system-level instruction contract that governs how agent sessions configure these systems.
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