Translations:Pacman troubleshooting/17/en
From Manjaro
It is therefore wise to first check to ensure that another installation is not (or had not been) in process at the time of the error. When satisfied that this is not the case, then the database lock file can be manually deleted. To do so, open up the terminal and enter the following command:
user $ sudo rm /var/lib/pacman/db.lck