While updating a WordPress plugin if you are getting the folloiwng issue:
Update failed: The update cannot be installed because we will be unable to copy some files.
This is usually due to inconsistent file permissions.
The solution is to run the following commands:
sudo groupadd www-my-grp
sudo chgrp -R www-my-grp /var/www
sudo chmod 2775 /var/www
sudo find /var/www -type f -exec chmod 2775 {} +
sudo find /var/www -type d -exec chmod 2775 {} \;
sudo chown -R www-data:www-my-grp /var/www/my.wordpresssite.com
sudo chmod -R 775 /var/www/my.wordpresssite.com
Running the above command will give the following permissions to yowur wordpress site:
drwxrwsr-x 11 www-data www-my-grp 4096 Jun 23 03:35 my.wordpresssite.com
Updating the wordpress plugin will work now and will give the Updated! status to you.