Ubantu : FTP details required during installation of themes and plugins

First you need to add the following code in your wp-config.php file.

define(‘FTP_USER’, ‘username’);
define(‘FTP_PASS’, ‘mypassword’);
define(‘FTP_HOST’, ‘192.168.2.132’);
define(‘FTP_SSL’, false);
But this is old idea. If you dont want to add the ftp access in wp-config.php file then Just add the following line wp-config.php file.

define(‘FS_METHOD’, ‘direct’);
Note: You need to give 755 permission to wp-content folder. Create the upgrade folder in wp-content folder.

If still you are facing issue then give 777 permission to all wp-content folder.

For permission use following command

cd your_wordpress_directory
sudo chown -R www-data wp-content
sudo chmod -R 755 wp-content
More information:

WordPress will try to write a temporary file to your /wp-content directory. If this succeeds, it compares the ownership of the file with it’s own uid, and if there is a match it will allow you to use the ‘direct’ method of installing plugins, themes, or updates.