Sometimes when running an automatic upgrade of your WordPress installation you may get the warning message, “Briefly unavailable for scheduled maintenance. Check back in a minute.”
WordPress places a hidden file on your web server called .maintenance. All you need to do to restore your website is delete the .maintenance file. To do this, either log in to your web server’s command line and rm the file. If you don’t know how to do this, then open an FTP client connection and you can delete the file this way too. Note that any files that begin with a dot are “hidden files,” so you will need to set your FTP client to display hidden files.
If the upgrade didn’t work the first time, you can run the automatic upgrade again after you remove the .maintenance file.
