unable to open post permalink in wordpress

Solution 1)   Add below syntax in .htaccess 

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress


Solution 2) Enable Apache rewrite mode and add below syntax in virtual host.

sudo a2enmod rewrite


<Directory /var/www/>
        Options Indexes FollowSymLinks MultiViews
        AllowOverride All
        Order allow,deny
        allow from all
</Directory>

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Issue : Showing Ftp Option While Installing Any Plugin Or Theme In Wordpress

Solution : Add below syntax to your wp-config.php

define('FS_METHOD','direct');

Conclusion : Due to Linux having such more restrictive file system,
         this will enable to you write directly to the folder.
         This will solve that ftp problem while installing a new plugin or theme.