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Description

MySQL Error 1878 indicates that the server failed to write data to a temporary file. These files are crucial for operations like sorting, complex joins, or handling large result sets. This error typically signifies an underlying issue with the server's file system, resource availability, or permissions.

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Error Message

Temporary file write failure.

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Known Causes

4 known causes

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Insufficient Disk Space

The server's disk partition where temporary files are stored has run out of free space, preventing MySQL from creating or writing to new temporary files.

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Incorrect File Permissions

The MySQL user or process lacks the necessary write permissions for the directory designated for temporary files (e.g., /tmp or a custom tmpdir).

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Disk Quota Exceeded

A user or group disk quota has been reached, even if overall disk space is available, preventing the MySQL process from writing more data.

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Filesystem Issues

The underlying filesystem where temporary files are stored may be corrupted, mounted as read-only, or configured with restrictive options.

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Solutions

4 solutions available

1. Increase Disk Space on Temporary Directory easy

Ensure the partition hosting the MySQL temporary directory has sufficient free space.

1

Identify the MySQL temporary directory. This is usually configured via the `tmpdir` system variable.

SHOW VARIABLES LIKE 'tmpdir';

2

Check the available disk space on the filesystem where the `tmpdir` is located. On Linux/macOS, you can use `df -h`.

df -h /path/to/your/tmpdir

3

If disk space is low, free up space by deleting unnecessary files or expanding the partition. Consider moving large temporary files from other directories if possible.

rm -rf /path/to/old/temp/file

4

Restart the MySQL server to ensure any changes to disk space are recognized and new temporary files can be created.

sudo systemctl restart mysql

2. Verify Permissions for MySQL User medium

Ensure the MySQL server process user has write permissions to the temporary directory.

1

Identify the MySQL temporary directory using `SHOW VARIABLES LIKE 'tmpdir';`.

SHOW VARIABLES LIKE 'tmpdir';

2

Determine the user that the MySQL server is running as. This is often 'mysql' on Linux systems.

ps aux | grep mysqld

3

Check the ownership and permissions of the temporary directory. The MySQL user needs read, write, and execute permissions.

ls -ld /path/to/your/tmpdir

4

If permissions are incorrect, grant the necessary permissions to the MySQL user. Replace 'mysql' with the actual MySQL user and '/path/to/your/tmpdir' with your directory.

sudo chown -R mysql:mysql /path/to/your/tmpdir
sudo chmod -R 755 /path/to/your/tmpdir

5

Restart the MySQL server after changing permissions.

sudo systemctl restart mysql

3. Adjust `tmpdir` to a Different Location medium

Configure MySQL to use a temporary directory on a different, more reliable filesystem.

1

Locate your MySQL configuration file (e.g., `my.cnf`, `my.ini`).

text

2

Edit the configuration file and add or modify the `tmpdir` setting under the `[mysqld]` section. Choose a directory on a filesystem with ample space and good performance.

[mysqld]
tmpdir = /new/path/to/mysql/tmp

3

Create the new temporary directory and ensure the MySQL user has ownership and write permissions.

sudo mkdir /new/path/to/mysql/tmp
sudo chown mysql:mysql /new/path/to/mysql/tmp
sudo chmod 755 /new/path/to/mysql/tmp

4

Restart the MySQL server for the changes to take effect.

sudo systemctl restart mysql

4. Monitor and Clean Up Temporary Files easy

Regularly monitor the temporary directory and remove stale or large temporary files.

1

Identify the MySQL temporary directory using `SHOW VARIABLES LIKE 'tmpdir';`.

SHOW VARIABLES LIKE 'tmpdir';

2

Periodically check the contents of the temporary directory for large or old files that are no longer needed. Files starting with `#` are often temporary files created by MySQL.

ls -lh /path/to/your/tmpdir

3

If you identify large, non-essential temporary files, you can safely remove them. **Caution:** Ensure MySQL is not actively using these files before deleting them. It's best to do this during a maintenance window or when the server load is low.

sudo rm -f /path/to/your/tmpdir/#sql_..._temp_file

4

Consider setting up a cron job to automatically clean up old temporary files (e.g., older than 24 hours).

find /path/to/your/tmpdir -type f -name '#sql_*' -mtime +1 -delete

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Related Errors

5 related errors

MySQL Error 1878: Temporary File Write Failure