Docker MySQL 8 how to set --secure-file-priv - mysql

Question

I would like to solve this problem:
ERROR 1290 (HY000): The MySQL server is running with the --secure-file-priv option so it cannot execute this statement
with the official MySQL 8 image on docker.
the command:
SHOW VARIABLES LIKE "secure_file_priv";
gives:
+------------------+-------+
| Variable_name | Value |
+------------------+-------+
| secure_file_priv | NULL |
+------------------+-------+
1 row in set (0.01 sec)
Is it possible to overwrite the default value NULL for the --secure-file-priv by using the official MySQL 8 Docker image?
the default value in this image is set to NULL
config/my.cnf
Perfectly I would like to set just an environmental variable or parameter when using docker run or create instead of bringing my own config file.
but if this is not possible then how to use custom config file?
is it possible that custom file just overwrites this one parameter and leaves others as they are in the official image config?

Answer 1

According to this documentation, you can configure secure-file-priv through command-line by passing --secure-file-priv=dir_name
secure-file-priv possible values are: empty string, dirname or NULL as explained in the privous url.
From mysql-docker page:
Configuration without a cnf file: Many configuration options can be passed as flags to mysqld. This will give you the flexibility to customize the container without needing a cnf file. For example, if you want to change the default encoding and collation for all tables to use UTF-8 (utf8mb4) just run the following:
$ docker run --name some-mysql -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql:tag --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci
So in our case would be like this:
dir_name should be a directory inside your container otherwise you will get the following error: mysqld: Error on realpath() on 'dir_name' (Error 2 - No such file or directory)
$ docker run --name some-mysql -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql:tag --secure-file-priv=dir_name
And now our change is committed in MySQL
mysql> SHOW VARIABLES LIKE "secure_file_priv";
+------------------+----------+
| Variable_name | Value |
+------------------+----------+
| secure_file_priv | dir_name |
+------------------+----------+
Alternatively, you can use a custom configuration file as explained in here:
Using a custom MySQL configuration file: The default configuration for MySQL can be found in /etc/mysql/my.cnf, which may !includedir additional directories such as /etc/mysql/conf.d or /etc/mysql/mysql.conf.d. Please inspect the relevant files and directories within the mysql image itself for more details.
If /my/custom/config-file.cnf is the path and name of your custom configuration file, you can start your mysql container like this (note that only the directory path of the custom config file is used in this command):
$ docker run --name some-mysql -v /my/custom:/etc/mysql/conf.d -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql:tag
This will start a new container some-mysql where the MySQL instance uses the combined startup settings from /etc/mysql/my.cnf and /etc/mysql/conf.d/config-file.cnf, with settings from the latter taking precedence.