In most cases, you can upgrade Centrify software on computers that are accessed by multiple users without entering single-user mode. However, upgrading authentication, authorization, and auditing services on a computer can potentially prevent users from logging on or using computer resources. If possible, you should perform upgrades when other users who might access the computer are logged off, then reboot the computer after completing the upgrade.
You should note that having all users logged off and rebooting the computer after an upgrade are not required steps, but are best practices to ensure the upgrade does not interrupt services for any users. In most cases, users who are already logged on are not affected by the upgrade. However, users who attempt to log on while files are being replaced during the upgrade process might be temporarily locked out of the managed computer you are upgrading.