FAQ

Common errors and fixes for MySQL and MariaDB backup operations.

Most MySQL backup failures fall into two categories: permission issues that prevent mysqldump from acquiring the locks it needs, and connection timeouts caused by large tables or slow queries. The entries below cover the most common cases and how to resolve them.

Backups fail after upgrading to MySQL 5.7.41 or 8.0.32

MySQL versions 5.7.41+ and 8.0.32+ require additional privileges for mysqldump to execute FLUSH TABLES. If your backups were working before a recent MySQL upgrade and are now failing, grant the required permissions to your backup user:

GRANT RELOAD, PROCESS ON *.* TO 'backup_user'@'%';
FLUSH PRIVILEGES;

Replace backup_user with the actual user SimpleBackups uses to connect to your database.

If granting permissions does not resolve the issue and you are using your own server, you can pin mysqldump to an earlier version (8.0.30) to work around the bug:

sudo apt-get install libncurses5
mkdir -p /opt/mysql && cd /opt/mysql
curl https://cdn.mysql.com/archives/mysql-8.0/mysql-8.0.30-linux-glibc2.17-x86_64-minimal.tar.xz | tar -xvJ
mv mysql-8.0.30-linux-glibc2.17-x86_64-minimal 8.0.30
sudo ln -s /opt/mysql/8.0.30/bin/mysqldump /usr/local/bin/mysqldump

Couldn't execute 'FLUSH TABLES WITH READ LOCK'

The error Couldn't execute 'FLUSH TABLES WITH READ LOCK': Access denied means your backup user lacks the RELOAD privilege. This privilege is required for mysqldump to acquire a consistent snapshot of MyISAM tables. Grant it with:

GRANT RELOAD ON *.* TO 'backup_user'@'%';
FLUSH PRIVILEGES;

For InnoDB-only databases, you can avoid the lock entirely by adding --single-transaction to your Custom Dump Flags in the backup settings.

mysqldump: Couldn't execute 'show create table'

The error Couldn't execute 'show create table table_name': Table is marked as crashed means a table is corrupted. Repair it with mysqlcheck before retrying the backup:

mysqlcheck -u username -p --repair database_name

To repair a specific table only:

mysqlcheck -u username -p --repair database_name table_name

If you have phpMyAdmin access, you can also repair via Operations → Table maintenance → Repair table. After the repair, re-run the backup to confirm it succeeds.

Error 2013: Lost connection during dump

The error Error 2013: Lost connection to MySQL server during query when dumping table occurs when a query takes longer than the net_read_timeout or net_write_timeout value. This is common with large tables.

Check your current timeout values:

SHOW VARIABLES LIKE 'net%timeout%';

Increase both to 900 seconds:

SET GLOBAL net_read_timeout = 900;
SET GLOBAL net_write_timeout = 900;

These values reset when MySQL restarts. To make them permanent, add them to your MySQL configuration file under [mysqld]:

[mysqld]
net_read_timeout = 900
net_write_timeout = 900