Silent Windows Installer installer without rebooting automatically

Currently I have an MSI which performs a major upgrade, and it is launche开发者_运维知识库d as:

msiexec.exe /i installer.msi /qn REBOOT=ReallySuppress

My question is regarding that particular property REBOOT=ReallySuppress: does this mean it will not restart the system but will do proper changes (if applied) when user reboot her system manually? Or will it simply ignore those things that require to restart the system?

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The installer performs all the operations. The value ReallySuppress of REBOOT property, or /norestart option, simply suppress system restart, if it's needed. And msiexec.exe exit code would be 3010 (ERROR_SUCCESS_REBOOT_REQUIRED) to indicate to the calling application that system restart is required.

The files that were in use during installation will have been moved out of the way and will be permanently deleted when system restarts. It is recommended to restart the system as soon as possible because until then some processes will be using the old (locked) files whereas new processes will be using the new, updated files, so there is room for ambiguity, especially since there may be registry changes as well. As such the /noreboot option is useful when you have several packages to install and you want to reboot after the last one, but only if it's absolutely necessary. Just ignoring the reboot prompt is not a good way to go.