How to prevent a MacBook from sleeping

pmset alone is not enough on a MacBook — the system still sleeps on lid-close or idle user-session timeouts. You need pmset (persistent settings) and a long-running caffeinate -simdu (active sleep assertion).

TL;DR

sudo pmset -a sleep 0 disksleep 0 hibernatemode 0 standby 0 autopoweroff 0 powernap 0
sudo pmset -a disablesleep 1

brew install tmux
tmux new -d -s caffeinate 'caffeinate -simdu'

Read on for what each piece does and alternatives to tmux.

1. Persistent settings with pmset

Plug in AC power, then:

sudo pmset -a sleep 0 disksleep 0 hibernatemode 0 standby 0 autopoweroff 0 powernap 0
sudo pmset -a disablesleep 1    # allow lid-closed operation without an external display

Verify:

pmset -g | grep -E 'sleep|hibernatemode|standby'

2. Active assertion with caffeinate

Keep a caffeinate process running for as long as you want the Mac awake:

caffeinate -simdu

Flags:

Flag	Prevents
-s	system sleep (AC)
-i	idle sleep
-m	disk sleep
-d	display sleep
-u	declares user activity

Pick whichever way keeps it running long enough for your use case.

Option A: Dedicated terminal window

Open a new Terminal/iTerm/Ghostty window and run:

caffeinate -simdu

Leave the window open. Closing the window or pressing Ctrl-C stops it.

Option B: nohup (background, survives logout)

nohup caffeinate -simdu >/dev/null 2>&1 &
disown

Check it is running:

pgrep -fl caffeinate

Stop it:

pkill caffeinate

Option C: tmux

brew install tmux           # if not installed
tmux new -d -s caffeinate 'caffeinate -simdu'

Reattach to inspect:

tmux attach -t caffeinate

Stop it:

tmux kill-session -t caffeinate

Option D: screen

screen -dmS caffeinate caffeinate -simdu

Reattach:

screen -r caffeinate

Stop it:

screen -S caffeinate -X quit

3. Verify

pmset -g assertions

You should see PreventUserIdleSystemSleep and PreventSystemSleep held by caffeinate.

Revert

pkill caffeinate
sudo pmset -a restoredefaults

Troubleshooting

• Still sleeps on lid close: confirm disablesleep is 1 in pmset -g.
• Docker hangs after wake: disksleep must be 0; restart Docker Desktop.
• Something else forces sleep: check pmset -g assertions for other processes (backup tools, VPNs) holding conflicting assertions.