错误提示：
(error) MISCONF Redis is configured to save RDB snapshots,
but it is currently not able to persist on disk.
Commands that may modify the data set are disabled,
because this instance is configured to report errors during writes if RDB snapshotting fails (stop-writes-on-bgsave-error option).
Please check the Redis logs for details about the RDB error.
首先想到有两种可能，一个是启动 redis 的用户没有写权限，二是磁盘满了
解决方法：
查看 redis 日志发现了是权限问题
12402:C 26 Nov 18:06:13.077 # Failed opening the RDB file root (in server root dir /var/spool/cron) for saving: Permission denied
30640:M 26 Nov 18:06:13.177 # Background saving error
换 root 用户启动 reids，或者使用 chown 命令授权即可。chown 命令使用
