DockerでMariadbが立ち上がらない（exited with code 1）

Question

DockerのMariadbのコンテナがすぐに下記のログを吐き出し、コンテナが終了します。

exited with code 1

dbのログと関連するコードが下記です。

db_1 | 2021-07-03 03:34:44+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 1:10.4.17+maria~focal started.

db_1 | 2021-07-03 03:34:46+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'


db_1 | 2021-07-03 03:34:46+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 1:10.4.17+maria~focal started.

db_1 | 2021-07-03 3:34:47 0 [Note] mysqld (mysqld 10.4.17-MariaDB-1:10.4.17+maria~focal-log) starting as process 1 ...

Dockerfile

FROM mariadb:10.4.17

RUN apt-get update && \
apt-get -y install locales-all

ENV LANG ja_JP.UTF-8
ENV LANGUAGE ja_JP:ja
ENV LC_ALL ja_JP.UTF-8
ENV TZ=UTC

COPY /docker/mysql/my.cnf /etc/my.cnf

my.conf

[mysqld]
explicit-defaults-for-timestamp= 1
character-set-server = utf8mb4
default-time-zone='Asia/Tokyo'
log-error = mysql-error.log
slow_query_log = 1
slow_query_log_file = mysql-slow.log
long_query_time = 1.0
log_queries_not_using_indexes = 0
general_log = 1
general_log_file = mysql-general.log

[mysql]
default-character-set = utf8mb4

[client]
default-character-set = utf8mb4

docker-compose.yml

  db:
    container_name: sample_db
    build:
      context: .
      dockerfile: ./docker/mysql/Dockerfile
    command: mysqld --character-set-server=utf8mb4 --collation-server=utf8mb4_general_ci
    ports:
      - ${DB_PORT}:3306
    volumes:
      - db-store:/var/lib/mysql
      - ./docker/mysql/initdb.d:/docker-entrypoint-initdb.d
    environment:
      - MYSQL_DATABASE=${DB_DATABASE}
      - MYSQL_USER=${DB_USERNAME}
      - MYSQL_PASSWORD=${DB_PASSWORD}
      - MYSQL_ROOT_PASSWORD=${DB_PASSWORD}

.ebv

DB_PORT=3306
DB_DATABASE=sample_db
DB_USERNAME=root
DB_PASSWORD=password

ログにエラーらしきものもないので詰まっております。
ご教授よろしくお願いします。