MySQL Error: "Could not increase number of max_open_files" - Explained

• max_open_files: This refers to a setting that controls the maximum number of files a process can have open at once. In this case, it's specifically for the MySQL or MariaDB server process.
• 4096: This is the current limit on the number of open files. On some systems, the default is set to a low value like 1024 or 4096.
• request: 4214: This indicates that MySQL or MariaDB tried to increase the limit to 4214 files, but failed.

There are two main reasons why this error might occur:

1. System-wide Limit: The operating system itself might have a hard limit set on the number of open files allowed for any process. This limit could be lower than 4214, preventing MySQL or MariaDB from raising its own limit.
2. Permissions: The user running MySQL or MariaDB might not have permission to change the process's resource limits.

# This command shows the current system-wide limit
ulimit -n

Increase System-wide Open File Limit (if necessary):

• Edit the system configuration file /etc/security/limits.conf (requires root access).
• Add a line like this for the user running MySQL/MariaDB (often mysql):

mysql soft nofile  <new_limit>
mysql hard nofile  <new_limit>

• Replace <new_limit> with a value higher than 4214 (choose wisely based on server needs).
• Save the file and restart the system for changes to take effect.

Alternatively, Increase Limit for MySQL/MariaDB process (if allowed):

• Edit the systemd service file for MySQL/MariaDB (e.g., /etc/systemd/system/mysql.service).
• Look for a section with options like LimitNOFILE or LimitMEMLOCK.
• Add or modify the line to specify the desired limit:

LimitNOFILE=<new_limit>

• Save the file and reload systemd configurations:

sudo systemctl daemon-reload

• Restart the MySQL/MariaDB service:

sudo systemctl restart mysql

Important Note:

• Increasing system-wide open file limits can impact other processes. Choose a new limit carefully based on your server's resource availability.
• It's recommended to consult your Linux distribution's documentation for specific instructions on modifying these configuration files.