So I ran into this problem. No matter what I did my WordPress installation displayed a stupid error that read as follows:
Briefly unavailable for scheduled maintenance. Check back in a minute.
Here is how to fix this problem with WP.
What is the hell is a .maintenance file in WP?
When you upgrade WP or plugin, it creates a .maintenance file WordPress installation directory. You can see this file with cat command:
$ cat .maintenance
<?php $upgrading = 1490382161; ?>
From the WordPress source code:
* Checks for a file in the WordPress root directory named “.maintenance”.
* This file will contain the variable $upgrading, set to the time the file
* was created. If the file was created less than 10 minutes ago, WordPress
* enters maintenance mode and displays a message.
So you need to wait for 10 minutes or simply delete this file using rm command or using ftp/sftp session to get rid of this annoying problem:
$ cd /var/www/html/
$ ls -l .maintenance
-rwxrwxrwx 1 www-data www-data 33 Mar 24 19:02 .maintenance
$ rm -v .maintenance
And my problem was solved.