mysql: [Warning] Using a password on the command line interface can be insecure.

MySQL 使用 mysqldump 导出数据库提示：

mysql: [Warning] Using a password on the command line interface can be insecure.

解决办法：

cat > /tmp/myconfig.cnf <<EOF
[client]
user = "root"
password = "123456"
EOF

docker cp /tmp/myconfig.cnf mysql:/tmp/

# 导出并压缩
docker exec -it mysql mysqldump --defaults-extra-file=/tmp/myconfig.cnf -uroot dbname | gzip > /tmp/dbname.sql.gz

# 解压：
gzip -d /tmp/dbname.sql.gz