Examples for creating Systemd service units.

create_systemd_service_unit-nginx+docker.sh

#!/usr/bin/env bash
set -eu

# Made for EC2 Amazon Linux 2 "user data" script, but should work most places
# FROM: https://gist.github.com/RichardBronosky/6c748146615140b1abc5489d43a4f75c

main(){
    [[ $UID -eq 0 ]] && sudo="" || sudo="sudo"
    install_docker
    install_systemd_unit
    [[ -n $sudo ]] && sleep 5 && $sudo systemctl status $service_name
}

install_docker(){
    $sudo yum update
    $sudo yum install -y docker
    $sudo systemctl enable docker
    $sudo systemctl restart docker
}

install_systemd_unit(){
    cmd="$(which docker)"
    image_name="nginx:alpine"
    service_name="nginx.service"
    service_desc="Nginx (in Docker) Service"
    service_start_pre=(
        "/bin/sh -c '"
            "$cmd stop %n ||:;"
            "$cmd rm   %n ||:;"
            "$cmd pull $image_name;"
        "'"
    )
    service_start=("$cmd run --rm --name %n -p 80:80 $image_name")
    service_stop=("$cmd kill --signal QUIT %n")
    service_log="/var/log/$service_name.log"
    service_unit="/lib/systemd/system/$service_name"
    service_work_dir="/tmp"
    service_start_with_logging=(
        "/bin/sh -c '"
            "{ echo; echo; date -u +%%FT%%TZ; echo; } >>$service_log;"
            "exec ${service_start[*]} >>$service_log 2>&1;"
        "'"
    )
    $sudo tee $service_unit >/dev/null <<EOF
[Unit]
Description=$service_desc
After=docker.service
Requires=docker.service
[Service]
WorkingDirectory=$service_work_dir
# Service Types: https://wiki.archlinux.org/index.php/systemd#Service_types
Type=simple
TimeoutSec=10
Restart=always
ExecStartPre=${service_start_pre[*]}
ExecStart=${service_start_with_logging[*]}
ExecStop=-${service_stop[*]}
[Install]
WantedBy=multi-user.target
EOF

    $sudo chmod 644 $service_unit
    $sudo systemctl daemon-reload
    $sudo systemctl enable $service_name
    $sudo systemctl reset-failed $service_name
    $sudo systemctl start $service_name
}

main

# vim: set et ts=4 sts=4 sw=4 :

create_systemd_service_unit-sample.sh

#!/usr/bin/env bash
set -eu

# A slightly Raspberry Pi specific Systemd service unit example.
# FROM: https://gist.github.com/RichardBronosky/6c748146615140b1abc5489d43a4f75c

service_name="sample.service"
service_desc="My Sample Service"
service_cmd="/usr/bin/python /home/pi/sample.py"

sudo tee /lib/systemd/system/$service_name >/dev/null <<EOF
[Unit]
Description=$service_desc
After=multi-user.target

[Service]
# To cd first:
#WorkingDirectory=/usr/local
# Service Types: https://wiki.archlinux.org/index.php/systemd#Service_types
Type=idle
ExecStart=$service_cmd
# Or, to save stdout and stderr to a log file:
#ExecStart=$service_cmd > /home/pi/$service_name.log 2>&1

[Install]
WantedBy=multi-user.target
EOF

sudo chmod 644 /lib/systemd/system/$service_name
sudo systemctl daemon-reload
sudo systemctl enable $service_name
sudo reboot