MySQL数据目录在docker image中保持默认-v标志

I am trying to start MySQL using docker image, I wanted to have a look at the binlog files, however I couldn't find them in /var/lib/mysql. From a few stackoverflow and Google reads, potential reason could be that mysql doesn't have permissions to write in /var/lib/mysql.
So I tried providing a different path using -v flag while starting the docker using the command docker run -it --rm --name mysql -p 3306:3306 -e MYSQL_ROOT_PASSWORD=debezium -e MYSQL_USER=mysqluser -e MYSQL_PASSWORD=mysqlpw -v /home/username/mysql debezium/example-mysql:1.1
However, even after this, datadir variable in client still remains /var/lib/mysql. Can someone help me in this?
Using docker run -it --rm --name mysqlterm --link mysql --rm mysql:5.7 sh -c 'exec mysql -h"$MYSQL_PORT_3306_TCP_ADDR" -P"$MYSQL_PORT_3306_TCP_PORT" -uroot -p"$MYSQL_ENV_MYSQL_ROOT_PASSWORD" to start the MySQL client.