Solve the error problem caused by modifying mysql data_dir

Today, I set up a newly purchased Alibaba Cloud ECS environment (Ubuntu 16.04 LTS). I need to save the MySQL data on the newly mounted disk (mounted to /mnt). First, I stop the MySQL service, and then check the location where the MySQL data is saved:

vi /etc/mysql/mysql.conf.d/mysqld.cnf

I found datadir＝/var/lib/mysql , which is the directory where the data is located, so I changed it to datadir=/mnt/mysql , then saved it, and finally copied the data saved in mysql to /mnt:

cp -r /var/lib/mysql /mnt
chown -R mysql:mysql /mnt/mysql

After the copy is complete, I thought everything was ready, so I started the mysql service:

systemctl start mysql

But I found that the startup failed, so I looked at the mysql error log:

tail -f -n100 /var/log/mysql/error.log

The error information is as follows:

[Warning] Can't create test file /mnt/mysql/iZwz9c03srb2lq9l374if5Z.lower-test

If you think about it carefully, there should be no problem with the mysql configuration. Check the apparmor configuration:

vi /etc/apparmor.d/usr.sbin.mysqld

The following configuration was found:

# Allow data dir access
/var/lib/mysql/ r,
/var/lib/mysql/** rwk,

What a pitfall. I just changed datadir的/var/lib/mysql , but it is still restricted here, so I changed it to:

# Allow data dir access
/var/lib/mysql/ r,
/var/lib/mysql/** rwk,
/mnt/mysql/ r,
/mnt/mysql/** rwk,

save. Restart the apparmor service:

service apparmor restart

Then start the mysql service again:

systemctl start mysql

The service finally started successfully. . .

The above is the editor's introduction to solving the error problem caused by modifying mysql data_dir. I hope it will be helpful to everyone. If you have any questions, please leave me a message and I will reply to you in time. Thank you very much for your support of the 123WORDPRESS.COM website!