add_updategrub-service

Install or refresh a systemd shutdown service that regenerates the GRUB configuration immediately before shutdown, reboot, or halt.

Version 1.0.1

When used with grub-btrfs, newly created Snapper snapshots may not be incorporated into the complete GRUB menu until grub-mkconfig is executed. This utility automates that step so newly created snapshot boot entries are available after the next reboot.

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Features

• Installs or refreshes a dedicated systemd shutdown service
• Automatically regenerates the GRUB configuration before shutdown, reboot, or halt
• Uses the distribution-neutral grub-mkconfig command
• Works with existing grub-btrfs installations
• Safe to rerun to refresh the installed helper and service
• Self-contained with no installation package required

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Requirements

• Linux system using systemd
• GRUB
• grub-mkconfig
• sudo

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Usage

Run the script as your normal user.

chmod +x add_updategrub-service.sh

./add_updategrub-service.sh

Do not run the script with sudo.

The script requests elevated privileges only when required.

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What Gets Installed

The utility installs or refreshes:

/opt/snapper/bin/update-grub-shutdown.sh

/etc/systemd/system/updategrub-shutdown.service

The service is enabled automatically.

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Use Case

This utility is intended for systems using grub-btrfs.

Whenever a new Snapper snapshot is created, the corresponding GRUB boot entry may not appear in the complete menu until grub-mkconfig has been executed.

The installed helper runs:

grub-mkconfig -o /boot/grub/grub.cfg

By updating the GRUB configuration during system shutdown, the latest snapshot entries are automatically available at the next boot without requiring any manual intervention.

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Compatibility

Tested on Debian, Ubuntu, Kubuntu, and CachyOS. The utility is designed for Debian/Ubuntu-based and Arch-based systems using systemd, GRUB, Snapper, and grub-btrfs.

Verified test cases

Distribution	Test case	Result
Debian	Installed and enabled the service; verified full GRUB regeneration during shutdown/reboot	Passed
Ubuntu	Installed, enabled, and executed the shutdown helper	Passed
Kubuntu	Installed, enabled, and executed the shutdown helper	Passed
CachyOS	Installed alongside grub-btrfsd and the Pacman GRUB hook; verified full shutdown regeneration	Passed

Version 1.0.1 was regression-tested on Debian and CachyOS after replacing the Debian-specific update-grub wrapper with grub-mkconfig -o /boot/grub/grub.cfg.

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Architecture

See ARCHITECTURE.md for the installed components, systemd lifecycle, and compatibility model.

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License

GPL-3.0-or-later