upgrade mysql 8.0 from 5.7 inplace

Sep 07 07:39:52 ntgmysql06.ap.acxiom.net mysqld[72973]: 2019-09-06T23:39:52.986257Z 0 [Warning] [MY-010441] [Server] Failed to open optimizer cost constant tables
Sep 07 07:39:52 ntgmysql06.ap.acxiom.net mysqld[72973]: 2019-09-06T23:39:52.986404Z 0 [ERROR] [MY-013129] [Server] A message intended for a client cannot ...'t exist
Sep 07 07:39:52 ntgmysql06.ap.acxiom.net mysqld[72973]: 2019-09-06T23:39:52.986419Z 0 [Warning] [MY-013129] [Server] A message intended for a client canno...inition.
Sep 07 07:39:52 ntgmysql06.ap.acxiom.net mysqld[72973]: 2019-09-06T23:39:52.986505Z 0 [ERROR] [MY-000067] [Server] unknown variable 'query_cache_type=0'.
Sep 07 07:39:54 ntgmysql06.ap.acxiom.net mysqld[72973]: 2019-09-06T23:39:52.986788Z 0 [ERROR] [MY-010119] [Server] Aborting
 

need to disable that option;

try to start service again:

Sep 07 07:58:56 ntgmysql06.ap.acxiom.net mysqld[74069]: 2019-09-06T23:58:56.455603Z 0 [ERROR] [MY-013129] [Server] A message intended for a client cannot be sent there as no client-session
Sep 07 07:58:56 ntgmysql06.ap.acxiom.net mysqld[74069]: 2019-09-06T23:58:56.455617Z 0 [Warning] [MY-013129] [Server] A message intended for a client cannot be sent there as no client-sessio
Sep 07 07:58:56 ntgmysql06.ap.acxiom.net mysqld[74069]: 2019-09-06T23:58:56.456026Z 0 [ERROR] [MY-010326] [Server] Fatal error: Can't open and lock privilege tables: Table 'mysql.user' does
Sep 07 07:58:56 ntgmysql06.ap.acxiom.net mysqld[74069]: 2019-09-06T23:58:56.456095Z 0 [ERROR] [MY-010952] [Server] The privilege system failed to initialize correctly. For complete instruct
Sep 07 07:58:57 ntgmysql06.ap.acxiom.net mysqld[74069]: 2019-09-06T23:58:56.456424Z 0 [ERROR] [MY-010119] [Server] Aborting
Sep 07 07:58:57 ntgmysql06.ap.acxiom.net mysqld[74069]: 2019-09-06T23:58:57.499797Z 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 8.0.17)  MySQL Community Serv
Sep 07 07:58:57 ntgmysql06.ap.acxiom.net systemd[1]: mysqld.service: main process exited, code=exited, status=1/FAILURE
Sep 07 07:58:57 ntgmysql06.ap.acxiom.net systemd[1]: Failed to start MySQL Server.
Sep 07 07:58:57 ntgmysql06.ap.acxiom.net systemd[1]: Unit mysqld.service entered failed state.
 

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mysqld --initialize-insecure
2019-09-07T00:05:56.474696Z 0 [System] [MY-013169] [Server] /usr/sbin/mysqld (mysqld 8.0.17) initializing of server in progress as process 74454
2019-09-07T00:05:56.476577Z 0 [ERROR] [MY-010457] [Server] --initialize specified but the data directory has files in it. Aborting.
2019-09-07T00:05:56.476588Z 0 [ERROR] [MY-013236] [Server] The designated data directory /var/lib/mysql/ is unusable. You can remove all files that the server added to it.
2019-09-07T00:05:56.476638Z 0 [ERROR] [MY-010119] [Server] Aborting
2019-09-07T00:05:56.476863Z 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 8.0.17)  MySQL Community Server - GPL.

ok, now I have to move all mysql folder out:

$mv /var/lib/mysql /var/lib/mysql2
and run again, Bingo, good to go now~~