Disabling Suspend/Sleep Mode on Ubuntu

This post describes how to prevent Ubuntu Server or Desktop from entering Suspend, Sleep, Hibernate, or Hybrid-Sleep mode — and how to verify the change and revert it if needed. The fix is essential for any machine accessed remotely over SSH.

[01] Environment and Situation

• OS: Ubuntu 22.04 / 24.04 (Server or Desktop)
• Symptom: SSH connection drops after a period of inactivity and cannot be re-established without physical access or a reboot
• Cause: The system enters Suspend or Sleep mode, suspending all network interfaces and terminating active sessions

This problem is most common on:

Use case	Why it hurts
Headless home or office server	No monitor or keyboard — impossible to wake remotely
Ubuntu Desktop used as a dev server	Desktop power settings are active even when logged out
CI / build runner on bare metal	Long builds trigger inactivity timeout mid-job
Remote NAS or media server	Sleep drops NFS/Samba shares for all clients

[02] Understanding the Sleep Targets

Ubuntu’s power-saving behaviour is managed by systemd through four sleep targets. Understanding each target helps you decide which ones to disable.

Target	Triggered by	What it does
sleep.target	Any sleep operation	Parent target — reached before the specific sleep type
suspend.target	Lid close, inactivity timeout	RAM stays powered (S3 state); wake is fast
hibernate.target	Manual command or critical battery	RAM written to swap, then power cut; wake is slow
hybrid-sleep.target	Manual command	RAM stays powered AND written to swap; tolerates power loss
suspend-then-hibernate.target	Long inactivity	Suspends first, then hibernates after a delay

By default, Ubuntu 22.04/24.04 enables all of these. You can check their current status with:

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

Figure 1. Default status — all four sleep targets are active and will respond to sleep requests from the system or desktop environment.

The output shows each target as active with Loaded: loaded and no masking. Any power event (inactivity timer, lid close, systemctl suspend) can start these targets.

[03] Disabling Sleep — systemctl mask

The recommended way to permanently disable the sleep targets is masking. Masking symlinks the unit file to /dev/null, which prevents systemd from starting the target under any circumstance — including requests from desktop environments, power daemons (UPower, logind), or systemctl suspend.

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

Figure 2. After masking — each target reports Loaded: masked and Unit sleep.target is masked, meaning no process can start it.

Why mask instead of disable?

Method	Effect	Can be overridden by?
systemctl disable	Removes the start symlinks from multi-user.target	A service that Wants=suspend.target can still start it
systemctl mask	Symlinks the unit to /dev/null — the unit cannot start at all	Nothing — masking is absolute

For a server that must never sleep, mask is the correct choice.

[04] Verifying the Change

After masking, confirm that the targets are truly inactive:

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

Each target should now show:

Loaded: masked (/dev/null; bad)
Active: inactive (dead)

You can also verify that logind (the daemon that triggers sleep on lid close or inactivity) will no longer act:

cat /etc/systemd/logind.conf | grep -i sleep
# Should show HandleSuspendKey=ignore or similar if you set it,
# but masking the targets is sufficient — logind cannot start a masked unit.

To test without rebooting, try issuing a manual suspend request and confirm it is blocked:

sudo systemctl suspend
# Expected: Failed to suspend system via logind: Sleep verb "suspend" is not supported

[05] Re-enabling Sleep (Revert)

If you later need to restore the default sleep behaviour — for example, when repurposing the machine as a laptop or desktop — unmask all four targets:

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

Figure 3. After unmasking — the targets return to their default active state and the system will respond to sleep requests again.

The change takes effect immediately; no reboot is required.

[06] Notes and Troubleshooting

Topic	Detail
Persistence	mask / unmask writes to /etc/systemd/system/ and survives reboots and OS minor updates
Desktop environment override	GNOME Power Settings and similar GUIs call logind, which calls systemd — masking the targets blocks this path too
Screen blanking is separate	Masking sleep targets does not prevent the display from turning off. Disable screen blanking via DPMS: xset -dpms && xset s off
Swap/hibernation dependency	If you unmask hibernate.target but have no swap space (common on cloud VMs), hibernation will fail — ensure swap exists first
Ubuntu Server minimal	On a server install without a desktop environment, only suspend.target is typically triggered; masking all four is still recommended for completeness
SSH still drops after fix	If sessions drop even after masking, check ClientAliveInterval / ServerAliveInterval in /etc/ssh/sshd_config — the issue may be a TCP keepalive timeout, not sleep