More weird; the GUI does contain the feature you want, but upon looking at the source code I found it is just named incorrectly:
Settings > Power > Suspend & Power Button > When the Power Button is pressed = Power Off actually prompts the user. It doesn't "Power Off". So for now set it to "Power Off". ** Changed in: gnome-control-center (Ubuntu) Assignee: (unassigned) => Daniel van Vugt (vanvugt) ** Changed in: gnome-control-center (Ubuntu) Status: Triaged => In Progress ** Description changed: Steps to reproduce: 1. Install Ubuntu 18.04 LTS 2. Login to session 3. Press ACPI Power button/key Expected behavior: * Ubuntu asks user about action Actual behavior: * Ubuntu immediately shutdowns - Workaround/fix: - gsettings set org.gnome.settings-daemon.plugins.power power-button-action interactive + Workaround/fix (1) + + gsettings set org.gnome.settings-daemon.plugins.power power-button- + action interactive + + Workaround/fix (2) + + Settings > + Power > + Suspend & Power Button > + When the Power Button is pressed = Power Off (actually does prompt the user) ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: ubuntu-desktop 1.417 ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17 Uname: Linux 4.15.0-20-generic x86_64 ApportVersion: 2.20.9-0ubuntu7 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Sat May 5 18:32:06 2018 InstallationDate: Installed on 2018-04-28 (7 days ago) InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426) SourcePackage: ubuntu-meta UpgradeStatus: No upgrade log present (probably fresh install) -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gnome-settings-daemon in Ubuntu. https://bugs.launchpad.net/bugs/1769372 Title: Prompt the user when the power button is pressed Status in gnome-control-center package in Ubuntu: In Progress Status in gnome-settings-daemon package in Ubuntu: Triaged Bug description: Steps to reproduce: 1. Install Ubuntu 18.04 LTS 2. Login to session 3. Press ACPI Power button/key Expected behavior: * Ubuntu asks user about action Actual behavior: * Ubuntu immediately shutdowns Workaround/fix (1) gsettings set org.gnome.settings-daemon.plugins.power power-button- action interactive Workaround/fix (2) Settings > Power > Suspend & Power Button > When the Power Button is pressed = Power Off (actually does prompt the user) ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: ubuntu-desktop 1.417 ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17 Uname: Linux 4.15.0-20-generic x86_64 ApportVersion: 2.20.9-0ubuntu7 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Sat May 5 18:32:06 2018 InstallationDate: Installed on 2018-04-28 (7 days ago) InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426) SourcePackage: ubuntu-meta UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1769372/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp