Power Management on Shani OS — Hibernation, Suspend, Battery Life, and Profiles

Laptops have specific requirements from an OS that desktops do not: hibernation that works reliably, battery optimisation, fast suspend/resume, and on encrypted systems, a way to unlock the disk at boot without typing a passphrase every time. Shani OS addresses all of these by default — without requiring post-install configuration.

This guide explains what is set up and how to use and customise it. Full reference: docs.shani.dev — Power & Suspend.

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Hibernation: Auto-Configured at Install

Hibernation saves your running session to disk and powers the machine completely off. On resume, you pick up exactly where you left off — open applications, documents, browser tabs.

On most Linux distributions, setting up hibernation requires manually calculating a swap offset, editing kernel parameters, and regenerating the initramfs. On Shani OS, all of this is handled during installation.

The installer:

Creates a dedicated @swap Btrfs subvolume with Copy-on-Write disabled (required for swap on Btrfs)
Creates a swapfile sized to match your installed RAM
Calculates the correct swap offset using btrfs inspect-internal map-swapfile
Embeds resume=UUID=... resume_offset=... into the Unified Kernel Image for each slot

When you hibernate (from the power menu or systemctl hibernate), the kernel writes RAM to the swapfile and powers off. On next boot, it reads from the swapfile and resumes your session.

Enabling Hibernate in the Power Menu

GNOME and KDE hide the hibernate option by default. To enable it:

GNOME:

# Check that hibernate is available
systemctl hibernate --no-pager --dry-run

# Enable hibernate in the power menu
# Install the Hibernate Status Button GNOME extension
flatpak install flathub org.gnome.Shell.Extensions
# Then search for "Hibernate Status Button" in Extension Manager (pre-installed)

KDE Plasma: KDE Plasma shows hibernate in the leave screen automatically when the swapfile is detected. If it is not showing:

# Check hibernate status
systemctl hibernate --dry-run

Manual Hibernate

# Hibernate immediately
systemctl hibernate

# Suspend-then-hibernate (suspend first, hibernate after a delay)
systemctl hybrid-sleep

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Suspend and Suspend-Then-Hibernate

Standard suspend (sleep) keeps RAM powered and suspends everything else. It is instant and uses very little battery. Shani OS uses the s2idle suspend state by default on most hardware, which is the modern, efficient option.

# Suspend immediately
systemctl suspend

# Suspend-then-hibernate (suspend now, hibernate after delay)
systemctl hybrid-sleep

To configure the delay before hibernate kicks in during hybrid sleep:

# Edit sleep configuration
sudo nano /etc/systemd/sleep.conf

# Add or modify:
[Sleep]
HibernateDelaySec=1800    # 30 minutes in suspend before hibernating

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Power Profiles

power-profiles-daemon is pre-installed and active. It provides three profiles that adjust CPU governor, platform power settings, and GPU power limits:

Balanced — default; appropriate for everyday use
Power Saver — extends battery life significantly; reduces CPU performance
Performance — maximises CPU and GPU performance; increases power draw

Switch profiles from the desktop:

GNOME: Top-right menu → Power → Performance / Balanced / Power Saver

KDE: System Settings → Power Management → Energy Saving → choose profile, or use the battery widget in the system tray

From the terminal:

# Check current profile
powerprofilesctl get

# List available profiles
powerprofilesctl list

# Switch profiles
powerprofilesctl set power-saver
powerprofilesctl set balanced
powerprofilesctl set performance

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LUKS2 Encryption and TPM2 Auto-Unlock on Laptops

If you enabled LUKS2 encryption during installation (recommended for all laptops), you are prompted for a passphrase at every boot by default. TPM2 auto-unlock eliminates this prompt — the LUKS key is sealed into your laptop's TPM2 chip, bound to PCR values 0 (firmware state) and 7 (Secure Boot policy). The disk unlocks silently on your own hardware. Move the disk to another machine or modify the firmware and it won't unlock.

One-time setup on first boot:

sudo gen-efi enroll-tpm2

After any firmware update (fwupdmgr update), PCR 0 changes and the passphrase will be required on the next boot — expected behaviour. After booting with the passphrase, re-enroll:

sudo gen-efi cleanup-tpm2 && sudo gen-efi enroll-tpm2

Full TPM2 reference including PCR policy selection, optional PIN, and keyslot management: gen-efi and Secure Boot on Shani OS · LUKS2 Encryption on Shani OS.

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Battery and Screen Management

Screen brightness, auto-suspend timeouts, and lid-close behaviour are configured through the standard desktop power settings.

GNOME: Settings → Power

Screen blank timeout
Automatic suspend when idle (on battery / plugged in)
Lid close action (suspend / hibernate / nothing)

KDE: System Settings → Power Management → Energy Saving

Separate profiles for battery and AC power
Screen dimming delay
Suspend/hibernate trigger
Lid close action

From the Terminal

# Get current battery status
upower -i /org/freedesktop/UPower/devices/battery_BAT0

# Watch battery status in real time
upower --monitor

# Set screen blank timeout (GNOME)
gsettings set org.gnome.desktop.session idle-delay 300

# Disable auto-suspend (GNOME)
gsettings set org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type 'nothing'
gsettings set org.gnome.settings-daemon.plugins.power sleep-inactive-battery-type 'nothing'

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Backlight and Display Power

# Check available backlight devices
ls /sys/class/backlight/

# Set brightness directly (replace intel_backlight with your device)
echo 500 | sudo tee /sys/class/backlight/intel_backlight/brightness

# DDC/CI monitor brightness (external monitors)
# ddcutil is pre-installed
ddcutil getvcp 10          # get current brightness
ddcutil setvcp 10 50       # set to 50%

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Troubleshooting Power Issues

Suspend Does Not Work / Machine Wakes Immediately

# Check what woke the machine
journalctl -b 0 -k | grep -i "wake\|acpi\|pm"

# List wake sources
cat /proc/acpi/wakeup

# Disable a wake source (e.g. USB keyboard waking from suspend)
echo XHCI | sudo tee /proc/acpi/wakeup

Hibernate Fails or Causes Boot Loop

# Verify swap is active
swapon --show

# Check the swapfile in @swap
ls -lh /swap/swapfile

# Verify the resume= parameter is in the UKI
sudo objcopy -O binary --only-section=.cmdline \
    /boot/efi/EFI/shanios/shanios-blue.efi /dev/stdout | strings | grep resume

If the resume offset is missing, regenerate the UKI:

sudo gen-efi generate --slot $(cat /data/current-slot)

TPM2 Unlock Fails After OS Update

The OS update regenerates both UKIs but does not change PCR values for the running slot. If something changed in the Secure Boot chain, boot with your passphrase then run sudo gen-efi cleanup-tpm2 && sudo gen-efi enroll-tpm2. Full recovery steps: gen-efi and Secure Boot on Shani OS.

Full power troubleshooting: docs.shani.dev — Power & Suspend.

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Summary for Laptop Users

After installing Shani OS on a laptop:

Enable LUKS2 encryption during the installer (strongly recommended)
Enroll TPM2 on first boot: sudo gen-efi enroll-tpm2 — eliminates passphrase at every boot (see gen-efi and Secure Boot)
Hibernate works immediately — swapfile is already sized and configured
Power profiles are available in the system menu — no setup required
Firmware updates via fwupdmgr update keep your BIOS and hardware secure
After any firmware update, re-enroll TPM2: sudo gen-efi cleanup-tpm2 && sudo gen-efi enroll-tpm2 (PCR 0 changes with each firmware update)

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Resources

Shani OS Troubleshooting Guide — when things go wrong
docs.shani.dev — Power & Suspend — troubleshooting reference
docs.shani.dev — TPM2 Enrollment — full TPM2 setup guide
Security Without Configuration — LUKS2 and security deep dive
Telegram community

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