start-stop-daemon: matching on world-writable pidfile /var/run/redis/redis-server.pid is insecurefailed
Microsoft Store上 看到最新的Ubuntu 20.04 LTS 已经适配到WSL上了, 于是卸载了老版本 18.04 LTS，安装上了最新版本的。
第一次启动会比较慢，需耐心等待，接着是创建用户帐户和密码(Ref-1)
Installing, this may take a few minutes...
Please create a default UNIX user account. The username does not need to match your Windows username.
For more information visit: https://aka.ms/wslusers
Enter new UNIX username:
看了下WSL的官方文档，发现WSL对各种数据库的支持(Ref-2)还真是蛮全的。 更让我惊喜的是WSL和Window其实可以互操作(Ref-3,Ref-4): 既可以从 Windows 命令行运行 Linux 工具，也可以从 Linux 命令行运行 Windows 工具。以前一直以为WSL只是提供了 Linux 模拟环境，可以让使用 Windows 的开发人员敲敲 Linux 命令，哈哈，认识真的太浅薄了。这对于Redis尤其有用，再也不用安装万年不变的3.2.100(Ref-5)了(当然也可以在Windows安装Docker Desktop，直接运行Redis--> docker run -d -p 6389:6389 redis，简单粗暴)。
启动运行Redis，解决启动问题
安装好Redis以后，在WSL中运行Redis
root@WSL:~# redis-server --version
Redis server v=5.0.7 sha=00000000:0 malloc=jemalloc-5.2.1 bits=64 build=636cde3b5c7a3923
root@WSL:~# sudo service redis-server start
Starting redis-server: redis-server.
root@WSL:~# redis-cli
127.0.0.1:6379> set Redis "Hello Redis!"
OK
127.0.0.1:6379> get Redis
"Hello Redis!"
设置Redis在后台运行，并查看当前进程(有两个Redis实例在运行，注意后台实例的启动PID是1738，运行子PID是1739)
root@WSL:~# redis-server --daemonize yes
1738:C 16 Aug 2020 18:03:11.055 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
1738:C 16 Aug 2020 18:03:11.055 # Redis version=5.0.7, bits=64, commit=00000000, modified=0, pid=1738, just started
1738:C 16 Aug 2020 18:03:11.056 # Configuration loaded
root@WSL:~# ps -aux --sort=tty,command
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.0 8892 284 ? Ssl 17:34 0:00 /init
redis 1602 0.0 0.0 61300 3836 ? Ssl 17:44 0:00 /usr/bin/redis-server 127.0.0.1:6379
root 1739 0.0 0.0 55668 2828 ? Ssl 18:03 0:00 redis-server *:6379
kevin 1643 0.0 0.0 18076 3528 tty1 S 17:46 0:00 -bash
root 1721 0.0 0.0 18080 3516 tty1 S 17:59 0:00 -bash
root 1642 0.0 0.0 8900 204 tty1 Ss 17:46 0:00 /init
root 1743 0.0 0.0 18880 1996 tty1 R 18:06 0:00 ps -aux --sort=tty,command
root 1720 0.0 0.0 18908 2680 tty1 S 17:59 0:00 sudo -i
把玩了一番，发现Redis无法启动，搜了一下，通过删除/var/run/redis/redis-server.pid 解决了问题。
root@WSL:~# sudo service redis-server start
Starting redis-server: start-stop-daemon: matching on world-writable pidfile /var/run/redis/redis-server.pid is insecurefailed
root@WSL:~# rm -f /var/run/redis/redis-server.pid
root@WSL:~# sudo service redis-server start
Starting redis-server: redis-server.
root@WSL:~# sudo service redis-server status
* redis-server is running
通过CMD或PowerShell运行 Redis
CMD/PowerShell 通过wsl命令进入WSL环境, 这时 WSL 会自动挂载当前目录(如何访问本地磁盘, 文件夹及文件)，也可以直接wsl redis-server(Ref-6)启动 Redis。Redis在standalone模式下，控制台无法进行交互。
C:\>wsl
kevin@WSL:/mnt/c# redis-server
2093:C 16 Aug 2020 18:44:15.097 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
2093:C 16 Aug 2020 18:44:15.097 # Redis version=5.0.7, bits=64, commit=00000000, modified=0, pid=2093, just started
2093:C 16 Aug 2020 18:44:15.097 # Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf
2093:M 16 Aug 2020 18:44:15.098 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 5.0.7 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in standalone mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 6379
| `-._ `._ / _.-' | PID: 2093
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
2093:M 16 Aug 2020 18:44:15.109 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
2093:M 16 Aug 2020 18:44:15.110 # Server initialized
2093:M 16 Aug 2020 18:44:15.111 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
2093:M 16 Aug 2020 18:44:15.113 * Ready to accept connections
直接挂载C盘根目录可能导致CTRL+C无法退出(常见的是权限问题), 在其他控制台，通过kill -9 PID可终止该Redis实例(2093)的运行(kill PID不起作用)。
2093:signal-handler (1597575573) Received SIGINT scheduling shutdown...
2093:M 16 Aug 2020 18:59:33.301 # User requested shutdown...
2093:M 16 Aug 2020 18:59:33.302 * Saving the final RDB snapshot before exiting.
2093:M 16 Aug 2020 18:59:33.303 # Failed opening the RDB file dump.rdb (in server root dir /mnt/c) for saving: Permission denied
2093:M 16 Aug 2020 18:59:33.304 # Error trying to save the DB, can't exit.
2093:M 16 Aug 2020 18:59:33.305 # SIGTERM received but errors trying to shut down the server, check the logs for more information
还可以通过redis-server &使Redis在后台运行, 和直接redis-server运行不同，CTRL+C关闭以后，通过ps命令查看，发现PID(2329)仍在运行, 但是这种后台模式和守护模式(daemonize yes)的STAT(Ref-7) 是不同的。
kevin@WSL:/$ redis-server &
[1] 2329
kevin@WSL:/$ 2329:C 16 Aug 2020 19:36:10.196 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
2329:C 16 Aug 2020 19:36:10.196 # Redis version=5.0.7, bits=64, commit=00000000, modified=0, pid=2329, just started
2329:C 16 Aug 2020 19:36:10.196 # Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf
2329:M 16 Aug 2020 19:36:10.197 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 5.0.7 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in standalone mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 6379
| `-._ `._ / _.-' | PID: 2329
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
2329:M 16 Aug 2020 19:36:10.202 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
2329:M 16 Aug 2020 19:36:10.202 # Server initialized
2329:M 16 Aug 2020 19:36:10.202 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
2329:M 16 Aug 2020 19:36:10.202 * Ready to accept connections
^C
kevin@WSL:/$ ps -aux --sort=tty,command
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.0 8892 264 ? Ssl 17:34 0:00 /init
redis 1602 0.0 0.0 61300 3836 ? Ssl 17:44 0:00 /usr/bin/redis-server 127.0.0.1:6379
root 1739 0.0 0.0 55668 2828 ? Ssl 18:03 0:00 redis-server *:6379
kevin 1643 0.0 0.0 18076 3084 tty1 S 17:46 0:00 -bash
root 1721 0.0 0.0 18212 3432 tty1 S 17:59 0:00 -bash
root 1642 0.0 0.0 8900 176 tty1 Ss 17:46 0:00 /init
root 1720 0.0 0.0 18908 2140 tty1 S 17:59 0:00 sudo -i
kevin 2178 0.0 0.0 18208 3684 tty2 S 19:12 0:00 -bash
root 2177 0.0 0.0 8900 200 tty2 Ss 19:12 0:00 /init
kevin 2333 0.0 0.0 18880 2000 tty2 R 19:36 0:00 ps -aux --sort=tty,command
kevin 2329 0.1 0.0 55668 4080 tty2 Sl 19:36 0:00 redis-server
