Ubuntu升級到了20.04之后，默認的rc.local是不啟動的，這也就導致了，我配置的一些自定義的腳本是沒有辦法在開機的時候就自動啟動了。
rc-local.service默認內容如下
# 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
這個時候啟動的時候會提示沒有Install，所以在如上的腳本上增加【Install】，下面是增加完【install】的全量腳本
# 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
[Install]
WantedBy=multi-user.target
Alias=rc-local.service
根據上面代碼中ExecStart，我們編輯/etc/rc.local腳本
#!/bin/sh
iptables-restore < /etc/iptables.up.rules #你需要開機自啟動的腳本或者命令
exit 0
這里一定要有exit的退出，否則會報錯的。
然后把rc-local.service設置為開機啟動
systemctl start rc-local # 啟動
systemctl restart rc-local # 重啟
systemctl status rc-local # 查看狀態，如果是active就表示沒問題了
