如何在Debian或Ubuntu Linux上失败时安装和配置监控程序，以重新启动Nginx/Apache/OpenVPN服务器等服务？

Monit是一个免费的开源软件，可充当过程监督。
它具有重启失败服务的能力。
您可以出于相同目的使用Systemd，daemontools或任何其他此类工具。
本教程显示了如何在Debian或Ubuntu Linux上将monit安装和配置为进程监督。

monit的作用是什么？

Monit是用于管理和监视Unix系统的小型开源实用程序。

Monit会进行自动维护和修复，并且可以在错误情况下执行有意义的因果操作。
具有系统监视和错误恢复所需的所有功能。
就像在服务器上使用带有工具箱的看门狗一样。
监视与本地主机或远程主机上的各种服务器的网络连接。
支持TCP，UDP和Unix域套接字。
网络测试可以在协议级别执行； Monit具有针对主要Internet协议(例如HTTP，SMTP等)的内置测试。
如果发生错误情况，例如，Monit可以采取行动。
如果sendmail未运行，则Monit可以自动再次启动sendmail，或者apache使用的资源过多(例如，正在进行DoS攻击)，Monit可以停止或重新启动apache并向您发送警报消息。

安装monit

执行以下apt-get命令/apt命令：

$ sudo apt-get install monit

如何在启动时启用监控服务？

执行以下命令：

$ sudo systemctl enable monit

如何启动/停止/重启监控服务？

语法为：

$ sudo systemctl status monit
$ sudo systemctl stop monit
$ sudo systemctl restart monit
$ sudo systemctl start monit

配置监控

您需要编辑以下文件：

• 主配置文件：/etc/monit/monitrc
• 进程/服务器特定文件的目录：/etc/monit/conf-available /和/etc/monit/conf-enabled /

让我们使用诸如vim命令或nano命令之类的文本编辑器来编辑/etc/monit/monitrc：

$ sudo vi /etc/monit/monitrc

或者

$ sudo nano /etc/monit/monitrc

首先设置警报接收者的电子邮件地址(必须将您的Linux框配置为路由电子邮件。

set alert admin@your-domain-name-here

使用以下语法可能只获得有关安全性的警报：

set alert security@your-domain-name-here on { checksum, permission, uid, gid }

请注意，默认情况下，monit在服务失败时仅发送一封电子邮件通知，而在服务恢复时则仅发送一封电子邮件通知。
例如，如果您希望在服务保持失败状态时每五个周期收到一次通知，则可以使用：

alert [email protected] with reminder on 5 cycles

启用嵌入式HTTP接口，该接口可用于查看监视的服务状态并通过Web界面管理服务：

set httpd port 2812 and
     use address localhost  # only accept connection from localhost
     allow localhost        # allow localhost to connect to the server and
     allow admin:monit      # require user 'admin' with password 'monit'

保存并关闭文件。

如何配置监视我自己的名为foo的进程的monit？

创建一个名为/etc/monit/conf-available/foo的文件：

$ sudo vi /etc/monit/conf-available/foo

追加以下配置：

check process foo
        matching "foo"
        start program = "/etc/init.d/foo start"
        stop program = "/usr/bin/killall foo"

保存并关闭文件。
启用它：

$ sudo ln -s /etc/monit/conf-available/foo /etc/monit/conf-enabled/

检查并运行monit控件/配置文件的语法检查：

$ monit -t
`Control file syntax OK`

重新加载monit，运行：

$ sudo /etc/init.d/monit reload

或者

$ sudo systemctl reload monit

如何为OpenVPN服务器配置监控程序？

OpenVPN是一个免费的开源VPN服务器，适用于Linux和类似Unix的系统。
确保OpenVPN由于某种原因死亡时启动：

$ sudo vi /etc/monit/conf-available/openvpn

追加以下配置：

check process openvpn  with pidfile /var/run/openvpn/server.pid
   group nogroup
   start program = "/etc/init.d/openvpn start"
   stop  program = "/etc/init.d/openvpn stop"
   if failed host localhost port 1194 then restart
   if 5 restarts with 5 cycles then timeout
   depend on openvpn_bin
 
check file openvpn_bin with path /usr/sbin/openvpn
   group nogroup
   include /etc/monit/templates/rootbin

保存并关闭文件。
启用它：

$ sudo ln -s /etc/monit/conf-available/openvpn /etc/monit/conf-enabled/

检查并运行monit控件/配置文件的语法检查：

$ monit -t
`Control file syntax OK`

重新加载monit，运行：

$ sudo /etc/init.d/monit reload

或者

$ sudo systemctl reload monit

如何配置监视MariaDB/MySQL服务器的监控程序？

$ cat /etc/monit/conf-available/mysql

输出示例：

check process mysqld with pidfile /var/run/mysqld/mysqld.pid
   group database
   group mysql
   start program = "/etc/init.d/mysql start"
   stop  program = "/etc/init.d/mysql stop"
   if failed host localhost port 3306 protocol mysql with timeout 15 seconds for 3 times within 4 cycles then restart
   if failed unixsocket /var/run/mysqld/mysqld.sock protocol mysql for 3 times within 4 cycles then restart
   if 5 restarts with 5 cycles then timeout
   depend mysql_bin
   depend mysql_rc
 
check file mysql_bin with path /usr/sbin/mysqld
   group mysql
   include /etc/monit/templates/rootbin
 
check file mysql_rc with path /etc/init.d/mysql
   group mysql
   include /etc/monit/templates/rootbin

如何为Nginx服务器配置监控？

$ cat /etc/monit/conf-available/nginx

输出示例：

check process nginx with pidfile /var/run/nginx.pid
   group www
   group nginx
   start program = "/etc/init.d/nginx start"
   stop program = "/etc/init.d/nginx stop"
   if 5 restarts with 5 cycles then timeout
   depend nginx_bin
   depend nginx_rc

check file nginx_bin with path /usr/sbin/nginx
   group nginx
   include /etc/monit/templates/rootbin

check file nginx_rc with path /etc/init.d/nginx
   group nginx
   include /etc/monit/templates/rootbin

如何为Apache服务器配置监控程序？

$ cat /etc/monit/conf-available/apache2

输出示例：

check process apache with pidfile /var/run/apache2/apache2.pid
   group www
   group apache
   start program = "/etc/init.d/apache2 start"
   stop program  = "/etc/init.d/apache2 stop"
   if 4 restarts within 20 cycles then timeout
   if failed host localhost port 80 with protocol http and request "/server-status" with timeout 25 seconds for 4 times within 5 cycles then restart
   depend apache_bin
   depend apache_rc
 
check file apache_bin with path /usr/sbin/apache2
   group apache
   include /etc/monit/templates/rootbin
 
check file apache_rc with path /etc/init.d/apache2
   group apache
   include /etc/monit/templates/rootbin

如何为OpenSSH SSHD服务器配置监控程序？

$ cat /etc/monit/conf-available/openssh-server

示例配置：

check process sshd with pidfile /var/run/sshd.pid
   group system
   group sshd
   start program = "/etc/init.d/ssh start"
   stop  program = "/etc/init.d/ssh stop"
   if failed host localhost port 22 with proto ssh then restart
   if 5 restarts with 5 cycles then timeout
   depend on sshd_bin
   depend on sftp_bin
   depend on sshd_rc
   depend on sshd_rsa_key
   depend on sshd_dsa_key
 
check file sshd_bin with path /usr/sbin/sshd
   group sshd
   include /etc/monit/templates/rootbin
 
check file sftp_bin with path /usr/lib/openssh/sftp-server
   group sshd
   include /etc/monit/templates/rootbin
 
check file sshd_rsa_key with path /etc/ssh/ssh_host_rsa_key
   group sshd
   include /etc/monit/templates/rootstrict
 
check file sshd_dsa_key with path /etc/ssh/ssh_host_dsa_key
   group sshd
   include /etc/monit/templates/rootstrict
 
check file sshd_rc with path /etc/ssh/sshd_config
   group sshd
   include /etc/monit/templates/rootrc

请记住，您必须使用ln命令链接这些文件并重新加载monit服务器。

$ cd /etc/monit/conf-enabled/
$ sudo ln -s /etc/monit/conf-available/openssh-server
$ sudo ln -s /etc/monit/conf-available/nginx
$ sudo ln -s /etc/monit/conf-available/mysql
$ sudo ln -s /etc/monit/conf-available/apache2
$ sudo monit -t
$ sudo /etc/init.d/monit reload

如何从CLI查看监控信息？

运行以下命令以查看monit的快速摘要：

$ sudo monit summary

输出示例：

The Monit daemon 5.16 uptime: 1h 9m 

Process 'openvpn'                   Running
File 'openvpn_bin'                  Accessible
System 'blr-theitroad-do-0001'       Running

要查看监视运行的状态：

$ sudo monit status

输出示例：
打印服务状态信息。

要仅查看有关openvpn进程的详细信息，请执行以下操作：

$ sudo monit status openvpn

输出示例：

The Monit daemon 5.16 uptime: 1h 15m 

Process 'openvpn'
  status                            Running
  monitoring status                 Monitored
  pid                               31577
  parent pid                        1
  uid                               65534
  effective uid                     65534
  gid                               65534
  uptime                            1h 17m 
  threads                           1
  children                          0
  memory                            6.1 MB
  memory total                      6.1 MB
  memory percent                    1.3%
  memory percent total              1.3%
  cpu percent                       0.0%
  cpu percent total                 0.0%
  port response time                2.091 ms to [localhost]:443 type TCP/IP protocol DEFAULT
  data collected                    Sun, 25 Jun 2016 00:12:40

如何查看监控日志文件？

您可以按以下方式使用tail命令：

$ sudo tail -f /var/log/monit.log

输出示例：

[IST Jun 24 23:54:40] info     : Starting Monit HTTP server at [localhost]:2812
[IST Jun 24 23:54:40] info     : Monit HTTP server started
[IST Jun 24 23:54:40] info     : 'blr-theitroad-do-0001' Monit reloaded

或按以下方式使用grep命令在日志文件中搜索内容：

$ grep foo /var/log/monit.log
$ grep sshd /var/log/monit.log
$ grep openvpn /var/log/monit.log

输出示例：

[IST Jun 24 22:55:28] info     : 'openvpn' start: /etc/init.d/openvpn

要从Web浏览器查看和控制监控，请在浏览器中执行服务器url(前提是您如上所述配置了set http)：

http://server1.theitroad.local:2812