config mysql by my.cnf but someitems don't work

[TINGTING GU]

i have docker run mysql by:
docker run --name mysql -d -p 3306:3306 -v /efs/data/mysql/cnf/:/etc/mysql/ -v /efs/data/mysql/data:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=xxxxxx -d mysql:5.7

when i set my.cnf as
[mysql]
default-character-set=utf8mb4

[client]
default-character-set=utf8mb4

[mysqld]
skip-name-resolve
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
server_id = 339393

configuration in mysqld didn't work, configuration in client and mysql worked.

>> mysqld --verbose --help i can see:
server-id 339393

>> mysqladmin variables -uroot -p
server-id 0

i don't know why? can you help me?