mysql启动报错------Another process with pid 2683 is using unix socket file.

测试库，重启报如下的错：

2019-04-25T09:59:02.628965+08:00 0 [Warning] Failed to set up SSL because of the following SSL library error: SSL context is not usable without certificate and private key
2019-04-25T09:59:02.628980+08:00 0 [Note] Server hostname (bind-address): '*'; port: 3309
2019-04-25T09:59:02.629024+08:00 0 [Note] IPv6 is available.
2019-04-25T09:59:02.629031+08:00 0 [Note]   - '::' resolves to '::';
2019-04-25T09:59:02.629035+08:00 0 [Note] Server socket created on IP: '::'.
2019-04-25T09:59:02.633093+08:00 0 [ERROR] Another process with pid 2683 is using unix socket file.
2019-04-25T09:59:02.633101+08:00 0 [ERROR] Unable to setup unix socket lock file.
2019-04-25T09:59:02.633104+08:00 0 [ERROR] Aborting

看到的提示是不能设置socket lock文件导致终止了，到对应的目录下面看了下，发现在mysql没有启动的时候有
-rw——-. 1 mysql mysql          6 Oct 17 10:00 mysql.sock.lock
这个文件存在，应该是因为存在了sock的锁文件，导致启动的时候不能创建该文件导致的失败，删除或改名备份后，再次启动正常。