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21.4. Configuration Examples
21.4.1. MariaDB Changing Database Location
When using Red Hat Enterprise Linux, the default location for MariaDB to store its database is
/var/lib/mysql/. This is where SELinux expects it to be by default, and hence this area is already labeled appropriately for you, using the
The location where the database is stored can be changed depending on individual environment requirements or preferences, however it is important that SELinux is aware of this new location; that it is labeled accordingly. This example explains how to change the location of a MariaDB database and then how to label the new location so that SELinux can still provide its protection mechanisms to the new area based on its contents.
Note that this is an example only and demonstrates how SELinux can affect MariaDB. Comprehensive documentation of MariaDB is beyond the scope of this document. See the official MariaDB documentation for further details. This example assumes that the mariadb-server and setroubleshoot-server packages are installed, that the
auditdservice is running, and that there is a valid database in the default location of
- View the SELinux context of the default database location for
ls -lZ /var/lib/mysqldrwx------. mysql mysql system_u:object_r:mysqld_db_t:s0 mysqlThis shows
mysqld_db_twhich is the default context element for the location of database files. This context will have to be manually applied to the new database location that will be used in this example in order for it to function properly.
- Enter the following command and enter the
mysqldroot password to show the available databases:
mysqlshow -u root -pEnter password: ******* +--------------------+ | Databases | +--------------------+ | information_schema | | mysql | | test | | wikidb | +--------------------+
- Stop the
systemctl stop mariadb.service
- Create a new directory for the new location of the database(s). In this example,
mkdir -p /mysql
- Copy the database files from the old location to the new location:
cp -R /var/lib/mysql/* /mysql/
- Change the ownership of this location to allow access by the mysql user and group. This sets the traditional Unix permissions which SELinux will still observe:
chown -R mysql:mysql /mysql
- Enter the following command to see the initial context of the new directory:
ls -lZ /mysqldrwxr-xr-x. mysql mysql unconfined_u:object_r:usr_t:s0 mysqlThe context
usr_tof this newly created directory is not currently suitable to SELinux as a location for MariaDB database files. Once the context has been changed, MariaDB will be able to function properly in this area.
- Open the main MariaDB configuration file
/etc/my.cnfwith a text editor and modify the
datadiroption so that it refers to the new location. In this example the value that should be entered is
[mysqld] datadir=/mysqlSave this file and exit.
mysqld. The service should fail to start, and a denial message will be logged to the
systemctl start mariadb.serviceJob for mariadb.service failed. See 'systemctl status postgresql.service' and 'journalctl -xn' for details.However, if the
auditdaemon is running alongside the
setroubleshootservice, the denial will be logged to the
SELinux is preventing /usr/libexec/mysqld "write" access on /mysql. For complete SELinux messages. run sealert -l b3f01aff-7fa6-4ebe-ad46-abaef6f8ad71The reason for this denial is that
/mysql/is not labeled correctly for MariaDB data files. SELinux is stopping MariaDB from having access to the content labeled as
usr_t. Perform the following steps to resolve this problem:
- Enter the following command to add a context mapping for
/mysql/. Note that the
semanageutility is not installed by default. If it is missing on your system, install the policycoreutils-python package.
semanage fcontext -a -t mysqld_db_t "/mysql(/.*)?"
- This mapping is written to the
grep -i mysql /etc/selinux/targeted/contexts/files/file_contexts.local/mysql(/.*)? system_u:object_r:mysqld_db_t:s0
- Now use the
restoreconutility to apply this context mapping to the running system:
restorecon -R -v /mysql
- Now that the
/mysql/location has been labeled with the correct context for MariaDB,
systemctl start mariadb.service
- Confirm the context has changed for
ls -lZ /mysqldrwxr-xr-x. mysql mysql system_u:object_r:mysqld_db_t:s0 mysql
- The location has been changed and labeled, and
mysqldhas started successfully. At this point all running services should be tested to confirm normal operation.