WordPress 3.9 upgrade fails

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When I try to upgrade a WordPress 3.8.1 site to 3.9, I get the following error:

The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.: wp-admin/includes/update-core.php

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Installation Failed

I’ve checked all the folders and files in the site, and they all the same permissions.

WordPress is running on Windows Server 2008 R2.

Must I go through the manual upgrade process, or is they a way to tell why I’m getting this error message?

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6 comments

  1. The only way I’ve found to make this work is to give your IIS user the Modify permission on the wp-admin folder and the WordPress files in the root. That user will be ApplicationPoolIdentity, IIS_IUSR, or something else depending on your IIS version.

    Obviously, this is a security risk. So I manually add those permissions when I need to upgrade and then remove it again when the upgrade is done.

    Here are the commands I use to automatically add the permissions:

    icacls [your path]*.php /grant BUILTINIIS_IUSRS:M
icacls [your path]license.txt /grant BUILTINIIS_IUSRS:M
icacls [your path]readme.html /grant BUILTINIIS_IUSRS:M
icacls [your path]wp-admin /grant BUILTINIIS_IUSRS:M

    And to remove them:

    icacls [your path]*.php /remove BUILTINIIS_IUSRS
icacls [your path]license.txt /remove BUILTINIIS_IUSRS
icacls [your path]readme.html /remove BUILTINIIS_IUSRS
icacls [your path]wp-admin /remove BUILTINIIS_IUSRS

  2. I found this question while searching for solution to same problem with update to WordPress 4.4.1 on Windows 2012 R2. Josh’s answer helped me find solution for my problem.

    Here is what I used to add the permissions:

    icacls [WordPress path] /grant IUSR:(OI)(CI)(M)

    And to remove:

    icacls [WordPress path] /remove IUSR

  3. The solution I found when I encountered this problem was to add the IUSR group in the security settings of the whole folder of your website. Once you are done with the update, remove it again.

  4. I had this same issue today. After searching for hours, one site mentioned:

    The wp-cron.php file should have 644 file permissions. If the
    wp-cron.php file permissions are not 644 then change the file
    permissions to 644.

    I made that change, and the automatic upgrade worked.

  5. I added these permissions for IUSR as suggested by @blu, but that by itself was not enough. For me I also had to add IIS_IUSRS with Modify permissions. After updating WordPress I removed the permissions again.

  6. Easier to do it through IIS Edit Permissions/Security Tab. Just grant Modify to Users account at the root directory of the website, Press apply, install the WordPress update (10 seconds), and then change the permissions back.