服务器上原本安装了mysql8.0版本，但是项目需要mysql5.7。
删除mysql8.0后安装mysql5.7，无法启动，出现故障如下：
Thread pointer: 0x0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0 thread_stack 0x40000
/usr/sbin/mysqld(my_print_stacktrace+0x3b)[0xf80ffb]
/usr/sbin/mysqld(handle_fatal_signal+0x486)[0x80ec06]
/lib64/libpthread.so.0(+0xf630)[0x7ff44c35b630]
/lib64/libc.so.6(gsignal+0x37)[0x7ff44ad43387]
/lib64/libc.so.6(abort+0x148)[0x7ff44ad44a78]
/usr/sbin/mysqld[0x7debd8]
/usr/sbin/mysqld(_ZN2ib5fatalD1Ev+0xfd)[0x13e622d]
/usr/sbin/mysqld[0x149df22]
/usr/sbin/mysqld[0x149e46b]
/usr/sbin/mysqld(_Z6fil_ioRK9IORequestbRK9page_id_tRK11page_size_tmmPvS8_+0x208)[0x14a9c98]
/usr/sbin/mysqld(_Z13buf_read_pageRK9page_id_tRK11page_size_t+0xe4)[0x1457ff4]
/usr/sbin/mysqld(_Z16buf_page_get_genRK9page_id_tRK11page_size_tmP11buf_block_tmPKcmP5mtr_tb+0x42d)[0x14273cd]
/usr/sbin/mysqld(_Z31trx_rseg_get_n_undo_tablespacesPm+0x15d)[0x13c538d]
/usr/sbin/mysqld[0x138d1b8]
/usr/sbin/mysqld(_Z34innobase_start_or_create_for_mysqlv+0x3996)[0x1391906]
/usr/sbin/mysqld[0x12572ff]
/usr/sbin/mysqld(_Z24ha_initialize_handlertonP13st_plugin_int+0x51)[0x861ae1]
/usr/sbin/mysqld[0xd62115]
/usr/sbin/mysqld(_Z40plugin_register_builtin_and_init_core_sePiPPc+0x2f0)[0xd68440]
/usr/sbin/mysqld[0x807164]
/usr/sbin/mysqld(_Z11mysqld_mainiPPc+0xa85)[0x80a985]
/lib64/libc.so.6(__libc_start_main+0xf5)[0x7ff44ad2f555]
/usr/sbin/mysqld[0x7fe5e4]
The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains
information that should help you find out what is causing the crash.
根据报错完全无法发现问题所在。
后来猜测是因为mysql8.0删除的不完全，故删除如下目录及文件，重新启动故障解决。
rm -rf /etc/my.cnf #mysql配置文件
rm -rf /var/lib/mysql #mysql数据目录目录可能不完全一样，需要根据具体部署目录删除。
