The error message "pg_dump: aborting because of server version mismatch" occurs when you're trying to create a PostgreSQL database backup, but the version  pg_dump doesn't match the version of the PostgreSQL server. This mismatch can happen if you've upgraded PostgreSQL on your server, and pg_dump from the older version is still being used.

To resolve this issue, follow these steps:

1. Determine the PostgreSQL Version:

   • First, determine the version of PostgreSQL that is currently running on your server. You can do this by connecting to PostgreSQL and running the following SQL command:

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     SELECT version();

   • This will display the PostgreSQL version number.

2. Locate the Correct pg_dump Binary:

   • Identify the location of the pg_dump binary that corresponds to the version of PostgreSQL you want to back up. PostgreSQL can have multiple versions installed on the same server, and each version has its own set of binaries.

   • Common locations for PostgreSQL binaries include /usr/bin, /usr/local/pgsql/bin, or a similar directory depending on your installation method.

3. Use the Correct pg_dump Binary:

   • Specify the full path to the pg_dump binary for the desired PostgreSQL version when creating your database backup. For example:

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     /path/to/correct/pg_dump -U your_username -d your_database > backup.sql

   • Replace /path/to/correct/pg_dump with the actual path to the pg_dump binary for the PostgreSQL version you want to use.

4. Verify the Backup:

   • After running the backup command, verify that the backup file (backup.sql in the example above) has been created successfully and contains the data you need.

By specifying the correct pg_dump binary for the PostgreSQL version, you should be able to create backups without encountering the version mismatch error.

If you have multiple versions of PostgreSQL installed on your server and need to switch between them frequently, consider adjusting your system's PATH environment variable to prioritize the directory containing the correct pg_dump binary for the version you intend to use.

The error message "pg_dump: aborting because of server version mismatch" occurs when there is a discrepancy between the version of PostgreSQL that pg_dump (the backup tool) is using the version of the PostgreSQL server that is running.

Here's how you can address this issue:

1. Check PostgreSQL Versions:

   • Verify the version of PostgreSQL installed on your server and the version that pg_dump is using. You can do this with the following commands:
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   # Check PostgreSQL version on the server psql --version # Check pg_dump version pg_dump --version

2. Update pg_dump:

   • If pg_dump is using an older version, you might need to update it to match the version of the PostgreSQL server. This can often be done by updating the PostgreSQL client packages.

   • For example, on Ubuntu, you can update the postgresql-client package:

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   sudo apt-get update sudo apt-get install postgresql-client

3. Verify Compatibility:

   • Ensure that the version of pg_dump is compatible with the version of PostgreSQL you're using. In some cases, there might be incompatibilities between major versions.

4. Specify Host and Port (if needed):

   • If you're connecting to a remote PostgreSQL server or using a non-standard port, make sure to specify the correct host and port in the pg_dump command.

   Example:

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   pg_dump -h your_postgres_host -p your_postgres_port -U your_username -d your_database > backup.sql

5. Check PATH Environment Variable:

   • Make sure that the directory containing the correct version  pg_dump is included in your system's PATH environment variable. This ensures that the correct version is used.

6. Consider Dumping Using SQL Format:

   • Instead of using pg_dump, you can try using pg_dumpall with the --file option to create a plain SQL dump:
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   pg_dumpall -h your_postgres_host -p your_postgres_port -U your_username --file=backup.sql

7. Check for Multiple PostgreSQL Installations:

   • If you have multiple versions of PostgreSQL installed on your server, ensure that you're using the correct version and that the pg_dump the command is associated with the right version.

8. Consult PostgreSQL Documentation:

   • Refer to the official PostgreSQL documentation for version-specific instructions and troubleshooting steps.

9. Contact PostgreSQL Community or Support:

   • If the issue persists, consider reaching out to the PostgreSQL community or support for further assistance.

By following these steps, you should be able to resolve the "server version mismatch" issue and create a backup of your PostgreSQL database successfully. Remember to always back up your data before making significant changes or performing critical operations.