While the commonly suggested method of masking systemd targets works superficially:

sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target

It creates significant overhead as systemd-logind continuously attempts and fails to suspend, resulting in:

• 100% CPU usage by systemd-logind
• Flooded system logs with permission denied errors
• Poor resource utilization on your server

The correct approach is to modify the Login Manager configuration:

sudo nano /etc/systemd/logind.conf

Uncomment and modify these lines:

HandleLidSwitch=ignore
HandleLidSwitchExternalPower=ignore
IdleAction=ignore

For complete control, combine with these configurations:

# Disable automatic suspend
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'

# Disable screen blanking (even without X)
sudo systemctl mask console-getty.service
sudo systemctl stop console-getty.service

After making changes, restart the login service and verify:

sudo systemctl restart systemd-logind
systemd-detect-virt  # Check if running as VM (may affect behavior)
journalctl -u systemd-logind -b | grep -i suspend  # Monitor for errors

For physical servers where you want to completely disable ACPI lid events:

sudo nano /etc/default/acpi-support
# Add or modify:
ACPI_LID=N

Then rebuild initramfs:

sudo update-initramfs -u

Create a test script to monitor suspension attempts:

#!/bin/bash
while true; do
    if grep -q "suspend" /proc/acpi/wakeup; then
        echo "Suspend still enabled on: $(grep "suspend" /proc/acpi/wakeup)"
        sleep 5
    else
        echo "Suspend properly disabled"
        break
    fi
done

---

When running Ubuntu 20.04 as a headless server, the default suspend behavior becomes problematic. While systemctl mask commands technically prevent suspension, they create a vicious cycle:

# This "solution" causes CPU spikes
sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target

You'll see constant log spam and 100% CPU usage from systemd-logind as it repeatedly attempts (and fails) to suspend:

journalctl -f
# Output:
systemd-logind[514]: Suspending...
systemd-logind[514]: Unit suspend.target is masked, refusing operation.
systemd-logind[514]: Failed to execute suspend operation: Permission denied

Instead of masking targets, we need to configure logind to ignore lid events entirely:

sudo nano /etc/systemd/logind.conf

Modify or add these key parameters:

HandleLidSwitch=ignore
HandleLidSwitchExternalPower=ignore
HandleLidSwitchDocked=ignore
IdleAction=ignore

For complete prevention of unwanted power state changes:

sudo systemctl unmask sleep.target suspend.target hibernate.target hybrid-sleep.target
sudo systemctl stop systemd-suspend.service
sudo systemctl mask systemd-suspend.service

Then create a udev rule to handle lid events:

sudo nano /etc/udev/rules.d/80-disable-lid-suspend.rules

Add this content:

# Disable lid switch handling
SUBSYSTEM=="input", ACTION=="change", ENV{LID_SWITCH}=="1", RUN+="/bin/true"

After making these changes:

sudo systemctl restart systemd-logind.service
sudo udevadm control --reload

Test by closing the lid and monitoring:

journalctl -f -u systemd-logind
uptime

You should see no suspension attempts and normal CPU usage.

For systems where sleep states should never be available:

sudo systemctl disable suspend.target
sudo systemctl disable hibernate.target
sudo systemctl disable hybrid-sleep.target

Then add kernel parameters:

sudo nano /etc/default/grub
# Append to GRUB_CMDLINE_LINUX_DEFAULT:
mem_sleep_default=deep noplymouth nosplash

Update GRUB:

sudo update-grub