Cannot install plugins even though www-data has write permissions

Question

All the files in my WordPress path are owned by myuser:www-data and Apache is running as www-data. All files and folders have group write permissions, e.g. -rw-rw----, but I keep being prompted for FTP details when I try to install a plugin.

If I chown the path to the www-data user, plugin installation and deletion work as expected, but then myuser cannot edit files. I could add myuser to the www-data group, but then myuser could access all other sites.

My files are chown'ed as follows:

chown -R myuser:www-data wordpress-folder/*

And chmod'ed as follows:

find wordpress-folder/ -type d -exec chmod 755 {} \;
find wordpress-folder/ -type f -exec chmod 644 {} \;

If my files are owned by the www-data group and are group-writable, then surely WordPress should be able to install plugins. Why can't WordPress install plugins?

Here is the output of ls -la in my plugins folder:

total 48
drwxrwx---  9 myuser www-data 4096 Aug  5 01:26 .
drwxrwx---  6 myuser www-data 4096 Aug  5 01:51 ..
drwxrwx---  6 myuser www-data 4096 Jul 10 16:27 disqus-comment-system
-rw-rw----  1 myuser www-data 6148 Jul 10 15:37 .DS_Store
drwxrwx---  7 myuser www-data 4096 Jul 10 16:30 gravityforms
-rw-rw----  1 myuser www-data   30 Jul 10 15:37 index.php
drwxrwx---  3 myuser www-data 4096 Jul 10 16:30 lime-export
drwxrwx---  6 myuser www-data 4096 Aug  1 11:17 mp6
drwxrwx---  6 myuser www-data 4096 Aug  5 01:26 rewrite
drwxrwx--- 10 myuser www-data 4096 Jul 10 16:38 wordpress-seo
drwxrwx---  7 myuser www-data 4096 Jul 24 17:14 wp-minify

Answer 1

If you add the following to your wp-config.php file it will force WordPress to use the 'direct' filesystem method:

define( 'FS_METHOD', 'direct' );

Answer 2

I think, I've answered a similar question here before. OP claims all file permission are set correctly but still ask for ftp credentials.

Well, this is very weird. But I think, it is still about permission.

Wordpress will write a temp file and compare the file owner by getmyuid() == @fileowner($temp_file_name).

If ture, it'll install the plugin directly without asking ftp details.

For more details, wp-admin/includes/file.php and get_filesystem_method function.

So, I would suggest you, write an independent php script in the root folder of wordpress installation to check out.

1, write a temp file

2, check the owner of the temp file

$dir = dirname(__FILE__);

$temp_file = $dir.'/wp-content/'.time();
$temp_handle = fopen($temp_file, 'w');
if ( $temp_handle ) {
    if ( getmyuid() == fileowner($temp_file) ){
        echo 'file owner correct';
    }

    fclose($temp_handle);
    unlink($temp_file);
}else{
    echo 'cant write file';
}

Answer 3

Simple workaround would be to add FTP credentials inside wp-config.php file, like this:

define( 'FTP_USER', 'username' );
define( 'FTP_PASS', 'password' );
define( 'FTP_HOST', 'ftp.example.org:21' );

But the problem might be related to your hosting using some different PHP process instead of suPHP.