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Fixing 'Unable to Open File' and Write Errors in All-in-One WP Migration

25 threads Sep 7, 2025 Plugin → All-in-one wp migration and backup

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If you've encountered errors like 'Unable to open file for reading', 'Unable to write to', or 'Unable to write header to file' while using the All-in-One WP Migration and Backup plugin, you're not alone. These are some of the most common issues users face during site export or import. This guide will walk you through the likely causes and the most effective solutions to get your migration back on track.

Why These Errors Occur

These errors are almost always related to server environment restrictions, not a problem with the plugin itself. The plugin needs to create, read, and write large temporary files in its storage folder during the backup and restore process. If the server has strict limits on file size, disk space, execution time, or file permissions, the process will fail, resulting in these frustrating errors.

Common Solutions to Try

1. Check and Increase PHP Configuration Limits

The most common culprit is a server PHP configuration that cannot handle the size of your website backup. You need to ensure the following values in your php.ini file are larger than your backup file:

  • upload_max_filesize
  • post_max_size
  • memory_limit
  • max_execution_time

If you do not have access to php.ini, you can often add these directives to your wp-config.php file or request your hosting provider to increase them for you.

2. Verify File and Folder Permissions

The plugin must have write permissions to its own directories. The necessary folders are:

  • wp-content/plugins/all-in-one-wp-migration/storage/
  • wp-content/ai1wm-backups/

Using an FTP client or your hosting file manager, check that these folders have the correct permissions (typically 755 or 775 for folders; 644 for files). In some cases, users have temporarily set them to 777 to test, though this is generally not recommended for security reasons long-term.

3. Confirm You Have Enough Disk Space

The export process requires free disk space significantly larger than your final .wpress file. A good rule of thumb is to have at least twice the size of your backup available. Contact your hosting provider to confirm your available disk quota if you are unsure.

4. Check for Hosting-Specific Restrictions

Some hosting providers impose hard limits on file sizes or execution times that cannot be overridden by standard php.ini changes. The easiest way to identify the specific limit you are hitting is to request your server's error logs from your hosting provider. The logs will clearly show which limit (e.g., mod_security, suPHP, or a custom rule) is blocking the process.

5. The Nuclear Option: Reinstall the Plugin

If permissions have become corrupted, a clean reinstall can often resolve the issue.

  1. Uninstall the All-in-One WP Migration plugin from your WordPress dashboard.
  2. Using FTP or your host's file manager, navigate to wp-content/plugins/ and ensure the all-in-one-wp-migration folder is completely deleted.
  3. Also, check the wp-content/ directory and delete the ai1wm-backups folder.
  4. Reinstall the plugin fresh from the WordPress plugin repository (Plugins -> Add New).

6. For Import Issues: Use the File via FTP Method

If you can export your site but run into 'Unable to open file for reading' during import, the upload process might be failing silently. A reliable workaround is to upload the file manually:

  1. Export your site and download the .wpress file.
  2. On the new site, use FTP to upload the file directly to the wp-content/ai1wm-backups/ folder.
  3. Go to the All-in-One WP Migration import screen on the new site. Your file should now appear in the list of backups, ready to be restored.

When to Contact Your Hosting Provider

If you have tried all the steps above and the problem persists, the issue is almost certainly a server-level restriction. Your next step should be to contact your hosting support, provide them with the exact error message, and ask them to:

  • Check the PHP and server error logs for relevant entries.
  • Confirm if there are any hard limits on file size, disk I/O, or execution time.
  • Ensure that no security modules (like mod_security) are blocking the plugin's operations.

By methodically working through these common causes, you can successfully resolve the file read/write errors and complete your website migration.

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