redis启动时，提示信息如下：
>>> redis-server
# oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
# Redis version=4.0.9, bits=64, commit=00000000, modified=0, pid=23974, just started
# Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf
* Increased maximum number of open files to 10032 (it was originally set to 1024).
# Creating Server TCP listening socket *:6379: bind: Address already in use
原因：
是因为linux中已经启动redis.
解决办法：
第一种（最简单）：
>>> /etc/init.d/redis-server stop
[ ok ] Stopping redis-server (via systemctl): redis-server.service.
更多关于redis命令：http://www.chenxm.cc/post/548.html
第二种方法：
找到redis-server的进程，然后杀死对应的进程，然后重新启动redis
>>> ps -ef | grep -i redis
root 3585 19590 0 10:36 pts/20 00:00:00 redis-server *:6379
user 3684 3663 0 10:38 pts/21 00:00:00 grep --color=auto -i redis
进程3585是redis的服务，
kill -9 3585
启动redis服务
>>> redis-server
# oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
# Redis version=4.0.9, bits=64, commit=00000000, modified=0, pid=3585, just started
# Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf
* Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 4.0.9 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in standalone mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 6379
| `-._ `._ / _.-' | PID: 3585
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
# WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
# Server initialized
# 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.
# WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.
* Ready to accept connections
