Display systemd init messages on the plymouth boot screen

journalctl_to_plymouth.sh

#!/bin/sh

journalctl --quiet -f -n0 --system -t systemd -o cat | while read -r line; do
	plymouth display-message --text="$line"
	if [ $? -ne 0 ]; then
		break
	fi
done
echo "Plymouth died, exiting..."

plymouth-boot-messages.service

# /etc/systemd/system/plymouth-boot-messages.service
# Run "systemctl enable plymouth-boot-messages.service" after creating the file

[Unit]
Description=Display boot messages on the plymouth screen
DefaultDependencies=no

# You may want these if your plymouth is not started by initramfs, but I want the script to take effect as soon as possible...
#After=plymouth-start.service
#Requires=plymouth-start.service

[Service]
Type=simple
ExecStart=/usr/local/bin/journalctl_to_plymouth.sh
RemainAfterExit=yes

[Install]
WantedBy=sysinit.target