Попробуйте использовать docker cp db:/var/log/mysqld.log -
для просмотра журнала mysqld
- возможно, это покажет, в чем проблема.
Хотя я не смог воспроизвести то, с чем вы столкнулись:
$ docker run --name db mysql/mysql-server:5.7
[Entrypoint] MySQL Docker Image 5.7.26-1.1.11
[Entrypoint] No password option specified for new database.
[Entrypoint] A random onetime password will be generated.
[Entrypoint] Initializing database
[Entrypoint] Database initialized
Warning: Unable to load '/usr/share/zoneinfo/iso3166.tab' as time zone. Skipping it.
Warning: Unable to load '/usr/share/zoneinfo/leapseconds' as time zone. Skipping it.
Warning: Unable to load '/usr/share/zoneinfo/tzdata.zi' as time zone. Skipping it.
Warning: Unable to load '/usr/share/zoneinfo/zone.tab' as time zone. Skipping it.
Warning: Unable to load '/usr/share/zoneinfo/zone1970.tab' as time zone. Skipping it.
[Entrypoint] GENERATED ROOT PASSWORD: 0h@ziGqAracLyPEqk@GkOd$YKg@
[Entrypoint] ignoring /docker-entrypoint-initdb.d/*
[Entrypoint] Server shut down
[Entrypoint] Setting root user as expired. Password will need to be changed before database can be used.
[Entrypoint] MySQL init process done. Ready for start up.
[Entrypoint] Starting MySQL 5.7.26-1.1.11
... в другом терминальном сеансе:
$ docker exec -it db mysqladmin --defaults-extra-file=/healthcheck.cnf ping
mysqld is alive
$ docker cp db:/var/log/mysqld.log - | tail -n 3
2019-05-10T18:51:08.472164Z 0 [Note] mysqld: ready for connections.
Version: '5.7.26' socket: '/var/lib/mysql/mysql.sock' port: 3306 MySQL Community Server (GPL)