Debian解决 /etc/rc.local 开机启动问题

前言

由于某些软件并没有增加开启启动的服务，很多时候需要手工添加，一般我们都是推荐使用 systemd 写个系统服务，但是对于一些简单的脚本或者懒人来说，添加命令到 /etc/rc.local 文件更方便，但是自从 Debian 9 开始，Debian 默认不带 /etc/rc.local 文件，而 rc.local 服务却还是自带的：

我们可以看到系统自带了服务

root@debian:~# cat /lib/systemd/system/rc-local.service
#  SPDX-License-Identifier: LGPL-2.1-or-later
#
#  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

并且它是默认关闭的

root@debian:~# systemctl status rc-local.service
● rc-local.service - /etc/rc.local Compatibility
     Loaded: loaded (/lib/systemd/system/rc-local.service; enabled-runtime; vendor preset: enabled)
    Drop-In: /usr/lib/systemd/system/rc-local.service.d
             └─debian.conf
     Active: failed (Result: exit-code) since Mon 2023-06-19 13:01:32 CST; 1min 32s ago
       Docs: man:systemd-rc-local-generator(8)
    Process: 517124 ExecStart=/etc/rc.local start (code=exited, status=1/FAILURE)
        CPU: 7ms

启用服务

那么如果我们想启用的话，首先要添加一个/etc/rc.local 文件：

cat <<EOF >/etc/rc.local
#!/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.

exit 0
EOF

在exit 0之前写要启动的命令即可

然后赋予它执行权限

chmod +x /etc/rc.local

接着启动服务

systemctl enable --now rc-local

root@debian:~# systemctl enable --now rc-local
The unit files have no installation config (WantedBy=, RequiredBy=, Also=,
Alias= settings in the [Install] section, and DefaultInstance= for template
units). This means they are not meant to be enabled using systemctl.
 
Possible reasons for having this kind of units are:
• A unit may be statically enabled by being symlinked from another unit's
  .wants/ or .requires/ directory.
• A unit's purpose may be to act as a helper for some other unit which has
  a requirement dependency on it.
• A unit may be started when needed via activation (socket, path, timer,
  D-Bus, udev, scripted systemctl call, ...).
• In case of template units, the unit is meant to be enabled with some
  instance name specified.
Job for rc-local.service failed because the control process exited with error code.
See "systemctl status rc-local.service" and "journalctl -xe" for details.

解决报错

其实上面的警告可以无视，但是下面的报错我们要找一下原因

我们按提示运行以下看看报错

systemctl status rc-local.service
● rc-local.service - /etc/rc.local Compatibility
     Loaded: loaded (/lib/systemd/system/rc-local.service; enabled-runtime; vendor preset: enabled)
    Drop-In: /usr/lib/systemd/system/rc-local.service.d
             └─debian.conf
     Active: failed (Result: exit-code) since Mon 2023-06-19 13:22:16 CST; 1min 40s ago
       Docs: man:systemd-rc-local-generator(8)
    Process: 590479 ExecStart=/etc/rc.local start (code=exited, status=1/FAILURE)
        CPU: 7ms

Jun 19 13:22:16 debian systemd[1]: Starting /etc/rc.local Compatibility...
Jun 19 13:22:16 debian rc.local[590482]: Neither the JAVA_HOME nor the JRE_HOME environment variable is defined
Jun 19 13:22:16 debian rc.local[590482]: At least one of these environment variable is needed to run this program
Jun 19 13:22:16 debian systemd[1]: rc-local.service: Control process exited, code=exited, status=1/FAILURE
Jun 19 13:22:16 debian systemd[1]: rc-local.service: Failed with result 'exit-code'.
Jun 19 13:22:16 debian systemd[1]: Failed to start /etc/rc.local Compatibility.

可以看到提醒我们java的环境变量没有配置，但是我们其实有配置过环境变量

root@debian:~# echo $JAVA_HOME
/home/java/jdk1.8.0_301

所以到底是为什么呢？

其实我们是在 /etc/profile 文件中设置了环境变量，但是 systemd 这个系统服务管理器可能并不能看到这些变量。因为 systemd 并不会加载 /etc/profile，所以在 /etc/profile 中设定的环境变量在 systemd 启动的服务中可能无法获取到。

解决的办法就是在 systemd 的服务定义文件中设定环境变量。你可以尝试在 rc.local 服务的 systemd 单元文件中设置 JAVA_HOME。

nano /lib/systemd/system/rc-local.service.d/debian.conf

在 [Service] 段下添加 Environment 行：

[Service] Environment=JAVA_HOME=/home/java/jdk1.8.0_301

我们保存并退出，然后重新加载‘systemd‘的配置文件

systemctl daemon-reload

之后再尝试启动‘rc.local‘服务就发现成功啦~

systemctl start rc-local.service

接着我们重新开启下systemd里rc-local服务的开机自启动就可以了

systemctl enable --now rc-local