When we install any software just by double clicking it, it creates some keys in HKLM and HKCU hives. There might be some settings or keys written to HKCU hive when installing a particular software and if that needs to be applied to all the users who use that software, in normal scenario of double clicking the setup.exe doesnt work. Hence, we need some monitoring tool which monitors all the changes to HKLM and HKCU hives and apply HKCU keys to all users who ever logs in. The tool which I am referring here is Install Application on Terminal Server option in control panel.

While installing a software if we open install application on terminal server and run the installation, it monitors HKLM and HKCU hives and applies any changes to HKCU to all users as HKLM is applied to the whole system. And mostly, while we run software installation with Install Application on Terminal Server option, it first changes the mode to installation mode.

We can install an application by .exe or .msi file. A .msi file will have all the info to change the installation mode while installing, but, Installing any application with “Install Application on Terminal Server option” is a best practice.

Whenever server reboots, it will be automatically set to /execute mode. If you have any software which requires mid install reboot, there might be an error after reboot is done and may not continue with the second half of the installation. This is because after reboot server automatically goes to /execute mode and not /install mode. Inorder to continue the installation after reboot, there are some keys created under,

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce

paths. Hence, allow first part of installation to complete, take a note of the keys mentioned at above location, delete those keys, and reboot. After reboot is complete, now change the installation mode to /install and run the same software to complete the installation.

Why should we put a server in install mode when installing any software?

When installing applications on multuser environment such as a Terminal/Citrix server, you must put the server into install mode, either via the command prompt or using Add/Remove programs wizard.

To put the server into install mode from command prompt type: change user /install To put serverback to execute mode after you’ve finished installing the app, type: change user /execute

When you install the application in Install mode, and information normally written to the HKEY_CURRENT_USER key will be written to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Terminal Server\Install

This key is then copied back to HKEY_CURRENT_USER when the user log son to the Terminal/Citrix Server.