Ubuntu 16.10開始不再使用initd管理系統，改用systemd，包括用systemctl命令來替換了service和chkconfig的功能。比如以前啓動mysql服務用
sudo service mysql start，現在用sudo systemctl start mysqld.service。systemd 默認讀取 /etc/systemd/system 下的配置文件，該目錄下的文件會鏈接/lib/systemd/system/下的文件。
執行命令ls /lib/systemd/system可以看到很多啓動腳本，其中就有我們需要的rc.local.service，打開腳本內容如下
# SPDX-License-Identifier: LGPL-2.1+
#
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
# This unit gets pulled automatically into multi-user.target by
# systemd-rc-local-generator if /etc/rc.local is executable.
[Unit]
Description=/etc/rc.local Compatibility
Documentation=man:systemd-rc-local-generator(8)
ConditionFileIsExecutable=/etc/rc.local
After=network.target
[Service]
Type=forking
ExecStart=/etc/rc.local start
TimeoutSec=0
RemainAfterExit=yes
GuessMainPID=no
一般啓動文件需要三個組成部分
[Unit]段: 啓動順序與依賴關係
[Service] 段: 啓動行爲,如何啓動，啓動類型
[Install] 段: 定義如何安裝這個配置文件，即怎樣做到開機啓動
上面少了[Install] 段，把下面Install段添上去
[Install]
WantedBy=multi-user.target
Alias=rc-local.service
Ubuntu-18.04 默認是沒有 /etc/rc.local 這個文件的，需要自己創建
sudo touch /etc/rc.local
前面我們說 systemd 默認讀取 /etc/systemd/system 下的配置文件, 所以還需要在 /etc/systemd/system 目錄下創建軟鏈接
sudo ln -s /lib/systemd/system/rc.local.service /etc/systemd/system/
然後把你需要啓動腳本寫入 /etc/rc.local，先寫測試腳本進行測試
#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
sudo echo "看到這行字，說明添加自啓動腳本成功" > /usr/local/text.log
exit 0
給rc.local加可執行權限
sudo chmod +x /etc/rc.local
啓動服務並檢查服務狀態
sudo systemctl enable rc-local
sudo systemctl start rc-local.service
sudo systemctl status rc-local.service
重啓後查看是否有text.log生成，以及寫入內容是否爲this just a test