system-update-pacman.service

# Some of the configuration in this unit was copied from:
#
# https://github.com/rpm-software-management/dnf-plugins-extras/blob/master/etc/systemd/dnf-system-upgrade.service

[Unit]
Description=Install system updates using pacman
DefaultDependencies=no

Requires=sysinit.target
After=sysinit.target systemd-journald.socket
Before=shutdown.target system-update.target

# `system-update.target` wants `system-update-cleanup.service`.
# `system-update-cleanup.service` removes `/system-update`
# and reboots the system.
# `system-update-cleanup.service` was added in systemd 233.
#
# Since we're not running as a oneshot service (see below),
# that service would start before the system update is complete.
# Fortunately, the dependency is a `Wants`, not a `Requires`,
# so we can use a `Conflicts` here
# to prevent `system-update-cleanup.service` from running.
Conflicts=system-update-cleanup.service

[Service]
# This unit is set up as a `simple` service.
# If it was set up as a `oneshot` service,
# then systemd would output "A start job is running for ..." messages
# through pacman's output.
Type=simple

# The command that performs the actual system update.
ExecStart=/usr/lib/systemd-system-update-pacman/perform-system-update

# Remove the symlink if it's still there, to protect against reboot loops.
ExecStopPost=/usr/bin/rm -fv /system-update

# If anything goes wrong, reboot back to the normal system.
FailureAction=reboot