There are couple of ways to see the password.
First Approach – Don’t Run container in daemon mode
Check the below command
docker run --name=mysql mysql/mysql-server:latest
and this will print the password in the terminal as look at the below logs
2020-05-28T23:41:01.418347Z 0 [System] [MY-011323] [Server] X Plugin ready for connections. Socket: '/var/run/mysqld/mysqlx.sock'
2020-05-28T23:41:01.666070Z 0 [Warning] [MY-010068] [Server] CA certificate ca.pem is self signed.
2020-05-28T23:41:01.714420Z 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.20' socket: '/var/lib/mysql/mysql.sock' port: 0 MySQL Community
Server - GPL.
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: PopiKQIjAS#OGj3x]yJOBLEn80p
[Entrypoint] ignoring /docker-entrypoint-initdb.d/*
2020-05-28T23:41:06.208480Z 10 [System] [MY-013172] [Server] Received SHUTDOWN from user root. Shutting down mysqld (Version: 8.0.20).
2020-05-28T23:41:07.861667Z 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 8.0.20) MySQL Community Server - GPL.
[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 8.0.20-1.1.16
2020-05-28T23:41:08.534785Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.0.20) starting as process 1
2020-05-28T23:41:08.549216Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
2020-05-28T23:41:09.135591Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
2020-05-28T23:41:09.369412Z 0 [System] [MY-011323] [Server] X Plugin ready for connections. Socket: '/var/run/mysqld/mysqlx.sock' bind-address: '::' port: 33060
2020-05-28T23:41:09.448584Z 0 [Warning] [MY-010068] [Server] CA certificate ca.pem is self signed.
2020-05-28T23:41:09.500464Z 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.20' socket: '/var/lib/mysql/mysql.sock' port: 3306 MySQL Communi
ty Server - GPL.
Second Approach – Run container in daemon mode & fetch the password from logs
Check the below command to run the container
docker run -d --name=mysql mysql/mysql-server:latest
and then run the below command to fetch the password
docker logs mysql 2>&1 | grep GENERATED
Output of above command is:
[Entrypoint] GENERATED ROOT PASSWORD: PopiKQIjAS#OGj3x]yJOBLEn80p
Once you have the password by one of the above-mentioned methods, you can then login with the below command using that password
docker exec -it mysql mysql -uroot -p
When asked, enter the generated root password (see the instructions above on how to find it). Because the MYSQL_ONETIME_PASSWORD option is true by default, after you have connected a mysql client to the server, you must reset the server root password by issuing this statement:
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'password';
Substitute password with the password of your choice. Once the password is reset, the server is ready for use.
Ref: https://hub.docker.com/r/mysql/mysql-server/