I have an issue recently while I try to upgrade my WP version to 5.4. That is because we don’t have a enough write permission on folders especially on Linux. So, we can resolve the issue by changing the permission temporary.
1. Change your WordPress root folder and sub-folders permission to 777 temporary.
$ chmod -R 777 public_website
2. Upgrade the WordPress version from WP admin console.
3. Change back the folders permission to 755.
$ chmod -R 755 public_website
4. Please verify the recommended permission from Admin console > WP Security > Filesystem security page. Normally we need to change back the 2 files permission as below.
$ chmod -R 644 public_website/wp-admin/index.php $ chmod -R 640 public_website/wp-config.php
That’s it. I hope this will help. 🙂