Hi,

Your /var/log/mysql/error.log has the following: [ERROR] [FATAL] InnoDB: Table flags are 0 in the data dictionary but the flags in file ./ibdata1 are 0x4000!

Are you attempting to open a mysql 8 database with mysql 5? I don't think that's supported. Make sure all traces of mysql 8 are removed (including databases) before installing mysql 5.

I'm marking this as invalid for now, but if this error really is caused during normal operation of mysql 5 without interference from an old mysql 8, please let us know and reopen the ticket. In such a case you should probably also check on the mysql bug tracker https://bugs.mysql.com/


Full error message:

2019-01-22T06:54:17.395378Z 0 [ERROR] [FATAL] InnoDB: Table flags are 0 in the data dictionary but the flags in file ./ibdata1 are 0x4000!
2019-01-22 12:24:17 0x7ff02a461740  InnoDB: Assertion failure in thread 140669478115136 in file ut0ut.cc line 942
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to http://bugs.mysql.com.
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.7/en/forcing-innodb-recovery.html
InnoDB: about forcing recovery.
06:54:17 UTC - mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
Attempting to collect some information that could help diagnose the problem.
As this is a crash and something is definitely wrong, the information
collection process might fail.

key_buffer_size=16777216
read_buffer_size=131072
max_used_connections=0
max_threads=151
thread_count=0
connection_count=0
It is possible that mysqld could use up to 
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 76387 K  bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

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 0x30000
/usr/sbin/mysqld(my_print_stacktrace+0x3b)[0xebde1b]
/usr/sbin/mysqld(handle_fatal_signal+0x48b)[0x790bbb]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x12890)[0x7ff028fbf890]
/lib/x86_64-linux-gnu/libc.so.6(gsignal+0xc7)[0x7ff0282bbe97]
/lib/x86_64-linux-gnu/libc.so.6(abort+0x141)[0x7ff0282bd801]
/usr/sbin/mysqld[0x7675ca]
/usr/sbin/mysqld(_ZN2ib5fatalD1Ev+0x66)[0x1094aa6]
/usr/sbin/mysqld[0x11426ec]
/usr/sbin/mysqld[0x1142c6d]
/usr/sbin/mysqld(_Z6fil_ioRK9IORequestbRK9page_id_tRK11page_size_tmmPvS8_+0x322)[0x114d6d2]
/usr/sbin/mysqld(_Z13buf_read_pageRK9page_id_tRK11page_size_t+0xdd)[0x11007fd]
/usr/sbin/mysqld(_Z16buf_page_get_genRK9page_id_tRK11page_size_tmP11buf_block_tmPKcmP5mtr_tb+0x4e5)[0x10d2555]
/usr/sbin/mysqld(_Z31trx_rseg_get_n_undo_tablespacesPm+0x14f)[0x1072dbf]
/usr/sbin/mysqld[0x103a218]
/usr/sbin/mysqld(_Z34innobase_start_or_create_for_mysqlv+0x2de6)[0x103e546]
/usr/sbin/mysqld[0xf05cc8]
/usr/sbin/mysqld(_Z24ha_initialize_handlertonP13st_plugin_int+0x4f)[0x7de31f]
/usr/sbin/mysqld[0xc99ce5]
/usr/sbin/mysqld(_Z40plugin_register_builtin_and_init_core_sePiPPc+0x1e5)[0xc9d1f5]
/usr/sbin/mysqld[0x788e70]
/usr/sbin/mysqld(_Z11mysqld_mainiPPc+0x785)[0x78a585]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7)[0x7ff02829eb97]
/usr/sbin/mysqld(_start+0x2a)[0x780c1a]
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.