在前面的笔记中，我们启动express项目都是使用命令“npm start”，如果是后台进程，需要借助nohup。

nohup npm start &

然后，怎么查看是否启动成功？

只能借助jobs或ps:

lee@mypc ~/works/nodejs/study21/log-morgan $ jobs
[1]+  Running                 nohup npm start &

lee@mypc ~/works/nodejs/study21/log-morgan $ ps -aux | grep 'npm'
lee       4062  0.0  0.0  13424  2436 pts/5    S+   10:15   0:00 grep --colour=auto npm
lee      30413  0.0  0.6 1069532 48752 pts/5   Sl   Jan18   0:00 npm 

怎么关闭进程？

只能借助kill:

lee@mypc ~/works/nodejs/study21/log-morgan $ kill 30413
lee@mypc ~/works/nodejs/study21/log-morgan $ ps -aux | grep 'npm'
lee       4180  0.0  0.0  13424  2444 pts/5    S+   10:18   0:00 grep --colour=auto npm

太麻烦了吧，有没有？!

其实，还可以这样启动：

pm2 start app.js

这样查看：

pm2 list
┌──────────┬────┬──────┬───────┬─────────┬─────────┬────────┬─────────────┬──────────┐
│ App name │ id │ mode │ pid   │ status  │ restart │ uptime │ memory      │ watching │
├──────────┼────┼──────┼───────┼─────────┼─────────┼────────┼─────────────┼──────────┤
│ demo1    │ 0  │ fork │ 0     │ errored │ 28      │ 0      │ 0 B         │ disabled │
│ app      │ 1  │ fork │ 0     │ stopped │ 0       │ 0      │ 0 B         │ disabled │
│ app      │ 2  │ fork │ 23174 │ online  │ 0       │ 18h    │ 36.695 MB   │ disabled │
│ app      │ 3  │ fork │ 0     │ stopped │ 0       │ 0      │ 0 B         │ disabled │
└──────────┴────┴──────┴───────┴─────────┴─────────┴────────┴─────────────┴──────────┘
 Use `pm2 show <id|name>` to get more details about an app

这样关闭：

pm2 stop 2

这样重启：

pm2 restart 2

简单，方便，使用，有没有？!

pm2是一个带有负载均衡功能的nodejs应用的进程管理产品，功能强大。它可以让应用保持后台运行，重启0等待。

pm2的安装和应用非常简单。

主要命令使用demo如下：

$ npm install pm2 -g            # Install PM2
$ pm2 start app.js              # Start, Daemonize and auto restart application
$ pm2 start app.js -i 4         # Start 4 instances of application in cluster mode
                                # it will load balance network queries to each app
$ pm2 start app.js --name="api" # Start application and name it "api"
$ pm2 start app.js --watch      # Restart application on file change
$ pm2 start script.sh           # Start bash script
 
$ pm2 list                      # List all processes started with PM2
$ pm2 monit                     # Display memory and cpu usage of each app
$ pm2 show [app-name]           # Show all informations about application
 
$ pm2 logs                      # Display logs of all apps
$ pm2 logs [app-name]           # Display logs for a specific app
$ pm2 flush
 
$ pm2 stop all                  # Stop all apps
$ pm2 stop 0                    # Stop process with id 0
$ pm2 restart all               # Restart all apps
$ pm2 reload all                # Reload all apps in cluster mode
$ pm2 gracefulReload all        # Graceful reload all apps in cluster mode
$ pm2 delete all                # Kill and delete all apps
$ pm2 delete 0                  # Delete app with id 0
$ pm2 scale api 10              # Scale app with name api to 10 instances
$ pm2 reset [app-name]          # Reset number of restart for [app-name]
 
$ pm2 startup                   # Generate a startup script to respawn PM2 on boot
$ pm2 save                      # Save current process list
$ pm2 resurrect                 # Restore previously save processes
$ pm2 update                    # Save processes, kill PM2 and restore processes
$ pm2 generate                  # Generate a sample json configuration file
 
$ pm2 deploy app.json prod setup    # Setup "prod" remote server
$ pm2 deploy app.json prod          # Update "prod" remote server
$ pm2 deploy app.json prod revert 2 # Revert "prod" remove server by 2
 
$ pm2 module:generate [name]    # Generate sample module with name [name]
$ pm2 install pm2-logrotate     # Install module (here a log rotation system)
$ pm2 uninstall pm2-logrotate   # Uninstall module
$ pm2 publish                   # Increment version, git push and npm publish