System Admin

13-Dec-05 22:16

Hi,

Can anyone tell me how Windows Update works? I mean how does it update the operating system, what type of files does it download and how the updates are seen in the Add-Remove programs dialog?

Anyone -- Help Cry | :((

Bikash Rai

Ray Cassick14-Dec-05 6:42

14-Dec-05 6:42

As far as I know the update files themselves are just Windows installer MSI files or exe files. They are downloaded to the machine and then run silently to install the update.

If the autoupdate wizard is activated the files are downloaded using BITS and then installed when you shut down and restart the system. If you have autoupdate activated you will see a new option on the shutdown screen that says 'install updates and shut down'.

I don't think there is very much magic here aside form the BITS implementation.

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HakunaMatada14-Dec-05 17:10

14-Dec-05 17:10

Yes I admit, read about the BITS implementation and its truly great, but the sad part, it doesn't work with winME and lower. Any free implemention similar to BITS but for WinME and lower?

Also, It does download MSIs, I think, but how the heck does it update the OS with MSIs. I want this in my own application but have no clue how to go about doing it.

Can you help? Sigh | :sigh:

Bikash Rai

Ray Cassick14-Dec-05 17:30

14-Dec-05 17:30

The problem there is that none of Windows desktop versions (95, 98, ME, SE) supported the concept of background services at all. All you had here were things that would run in the system tray.

The server OSes (Windows NT, 2000, 2003) and XP do support them.

I don't think there would be anything from stopping you from writing an app that does what BITS does and setting it up to run in the system tray. Well, nothing aside form the fact that some of the older OSes do not support the .NET run time an way.

Updating the OS is nothing new. The MSI file (or EXE file) gets run in a silent mode (no UI) and then you are prompted to reboot when you need to.

What is it that you are exactly trying to do here?

HakunaMatada14-Dec-05 17:58

14-Dec-05 17:58

Thank you for the prompt reply. Its people like you, willing to help others, which makes the programming world a better place to code in. Smile | :)

Well, I do know that the MSIs can be run in Silent mode using the /q option but how do you create an update for an application using MSIs? I googled and found out that patches for applications can be made (.msp) but to use an MSI means to reinstall everthing. Now how do I use an MSI to reinstall everthing with the applciation running? Also, I would not want to package the whole application in the MSI, just the updates or patches. Of course, I could just download the changed files and update the application, but I would like to do this through a MSI file or an installation file.

Can you help? Sigh | :sigh:

Bikash Rai

Ray Cassick14-Dec-05 18:16

14-Dec-05 18:16

Aw shucks

If you are creating the installer for your application part of that will have to be knowing how to handle cases where you try to copy a file over where one exists already and get an error showing that it is already in use. This is why installers tell people that they need to reboot after installing an update, to allow the files to be copied upon reboot before the application has been started up again.

This is typically done by the installer writing a small batch file on the fly that shows where files need to be copied (and from where - like a temp area) then placing a reference to the batch file into the Windows registry in the RunOnce key. The idea behind this key is that any executable file listed here is run on the next reboot, but Windows knows that (because it is called the RunOnce key) that once this file is run the reference to it is removed (so it is not run again, and again, and again...)

Doing all this is something that you need to manage in what ever tool you use to write your installations. Usually tools like Installshield and such handle this for you.

You could also have the installer look to see if the application is it trying to update is running and then either warn the user to close it first and retry the install or just close it yourself and restart it when your installer is done.

Until Windows Vista arrives, no matter what you do you will always have to deal with files that are in use and figure out what to do. Vista will have some things in place to handle this a bit better so you should not have to reboot as much as you do now, but until then you are on your own as to what to do. Depending on what you are updating (user level application or a system service or device driver) you will need to deal with files that are in use.

Personally, if you are updating something like a system service you can always just tell the user that you have to stop the service to do the update, then use the SCM APIS to stop the service, install the new files and then restart the service. Just keep in mind things like user security levels (The person running the update might not have the same security access as the person that installed the service in the first place so you might not be able to do this.

When I do updates, if I am just updating one file I only write that one file to keep the installer small. I know other people that install an entire new version of the application and only change one file. Again, it is up to you.

Good luck...

HakunaMatada14-Dec-05 18:38

14-Dec-05 18:38

Hi Ray,

Thanks a mil. Smile | :)

Just one small question though. Supposing I update the application using the method you told me, and it replaces the file in question, will the update be visible in the Add-REmove programs list. Supposing I add a new dll file to the update which was not there during the original installation, will the original uninstaller be able to detect the addition of the new dll file and do a clean uninstall? I want the original installer to detect the changes made by the updates. Also is it possible to make the updates visible in the Add-Remove programs so that the updates can be removed by the user if he/she wants?

Lastly, I am using VS.NET 2003 and the installer I use is the one that comes with VS.NET 2003.

Sorry for the volley of questions and thanks for helping. Smile | :)

Bikash Rai

Ray Cassick14-Dec-05 18:51

14-Dec-05 18:51

The installer engine should be taking care of listing things in the add-remove programs list for you. That is what the installer engine in there for. Also, managing what happens upon un-install should be managed by that as well.

To be honest I have never looked into how the engine does it though so I am not sure how it knows what files to put back if you un-install an update that had replaced files.

I have seen some installers explicitly ask you where you want the originals backed up and then they create that folder and copy the original files there but I am not sure if that is just the fault of their installer engine or not.

If you make the updates visible on the add remove list then why worry about if the original installer will remove files that you added ad updates. Typically installers will NOT touch files, folders or registry entries that they did not put there. They do this to make sure that they do not inadvertently remove a file that they are not supposed to (like a users data file). This is how systems can get cluttered with 'stuff' after an application is un-installed. This is what system cleaners take care of.

HakunaMatada14-Dec-05 18:55

14-Dec-05 18:55

Thanks Ray.

Any idea about the AVG Antivirus and where it stores it scheduled update information.

Bikash Rai

Ray Cassick14-Dec-05 19:13

14-Dec-05 19:13

Nope, but I bet using Filemon from Sysinternals.com[^]and a few trys watching the update run I could find out.

Applications like that typically have their own custom updating schemes though. My quick guess is that they do one of the following:

1) Create a folder in user isolated storage, download the updates there and then put the files (uncompressing where needed) into the proper spots, then stop and restart their service...

2) Download the updated signatures and stuff into a temp folder in the temp directory and deal with them form there.

HakunaMatada14-Dec-05 19:23