The error message "Upgrade after a crash is not supported" typically occurs when you attempt to start MySQL or MariaDB after a crash without performing the necessary recovery steps. This situation can arise if the database files are not shut down properly, potentially leading to corruption.

To address this issue, follow these steps:

1. Backup Your Data (if possible):

   • Before proceeding, make sure to back up your MySQL/MariaDB data directory. This will safeguard your data in case further actions inadvertently worsen the situation.

2. Check Database Logs:

   • Review the MySQL/MariaDB error logs (usually located in /var/log/mysql/ or /var/log/mariadb/) for any additional information on what caused the crash and if there are any corruption indications.

3. Start MySQL/MariaDB in Recovery Mode:

   • To initiate recovery, you'll need to start MySQL/MariaDB in recovery mode, which allows you to run specific commands to fix potential issues. The exact command can vary based on your Linux distribution and whether you're using MySQL or MariaDB:

   • For MySQL:

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     sudo mysqld --innodb_force_recovery=1 --user=mysql --datadir=/var/lib/mysql

   • For MariaDB:

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     sudo mariadb --innodb-force-recovery=1 --user=mysql --datadir=/var/lib/mysql

   • Note that --innodb_force_recovery=1 is a starting point. If it doesn't work, you can try increasing the value (up to 6) to apply more aggressive recovery techniques. However, higher values may lead to data loss.

4. Repair and Optimize Tables:

   • After starting in recovery mode, you can try to repair and optimize the tables in the database.
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   USE your_database_name; REPAIR TABLE your_table_name; OPTIMIZE TABLE your_table_name;
   • Replace your_database_name and your_table_name with the actual database and table names.

5. Restart MySQL/MariaDB:

   • Once you've performed the necessary recovery steps, try restarting MySQL/MariaDB normally.
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   sudo systemctl restart mysql # For MySQL sudo systemctl restart mariadb # For MariaDB

6. Check Database Integrity:

   • After restarting, monitor the database logs for any errors or warnings that might indicate ongoing issues.

7. Monitor System Resources:

   • Ensure that your server has sufficient resources (CPU, memory, disk space) to handle the database operations.

8. Verify Data Integrity:

   • Log in to the database and verify the integrity of your data. Check for any missing or corrupted records.

9. Consult Database Administrator:

   • If you're unsure about any of the steps or if the issue persists, consider consulting a database administrator or expert for further assistance.

If none of the above steps resolve the issue, it's recommended to contact a professional database administrator or support from your hosting provider for specialized assistance.