Adding an external CAB to an MSI with an internal

Question

I have a visual studio installer (vs2015) that installs an application. I want it to also install a set of configuration files, the contents of which vary by physical install location, that will be delivered as a cab file in the same directory as the msi. The cab has a known set of files that will be distributed across 2 folders in the install location and is created by a different project than the installer. How do I get the msi to install both its internal contents and the contents of the external cabinet file?

Answer 1

Wise Package Studio

I actually successfully updated MSI files with new files to install using Wise Package Studio back in the day. It added a CAB file to the Cabs table (I don't know if this table is actually a Wise "view" or a real MSI table - it seems missing from Orca if all CABs are embedded in the MSI). There is a corresponding entry in the Media table where the LastSequence value (in the Media table) describes which CAB contains what files. In the File table you will find a field called Sequence which specifies the "order" of the files listed. Essentially your new files will be at the end of the "order" and hence in a new CAB. A bit involved the whole thing.

However, I successfully got Wise Package Studio to both embed a new CAB file, and to use an external CAB file to install the new files during installation, but I don't have the procedure documented and don't recall all the steps. Moreover I don't recommend the procedure - in fact I would never use this approach now. It was just used at the place I worked at the time. In most cases we used a transform to add this content to the main package, rather than hacking the MSI itself.

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MSI SDK: Including a Cabinet File in an Installation

The procedure to add a CAB file to your MSI is documented in the MSI SDK here: Including a Cabinet File in an Installation. Quite involved - as I said, but definitely possible. As you will see the lack of a # flag at the start of the CAB name in the Media table indicates an external CAB file.

So I suppose, in short:

1. Add a new entry to the file table, set the Sequence number to +1 from the highest sequence File entry already there. I would add a new, corresponding entry in the Component table as well.
2. Add a new row to the Media table, specify the number you set for the file in the LastSequence column. Add the name of your cabinet file to Cabinet. Make sure to not prefix the CAB name with #.
3. Wise would also add entries in the MsiFileHash table. Not sure if this is required or not. Pretty sure it is not required to add entries here.
4. As you will see in the linked MSI SDK article, you can embed the whole cab following the last few steps listed in the linked MSDN content.

I wish I had time to test all this, but I don't. Which brings me to the next point:

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Default / Instantiate Your Settings?

When I see questions like these I invariably ask myself: what is in these files? Are they "trivial settings" that could actually be defaulted instead of hard coded in config files? This has saved me a lot of work, many times.

The deployment of settings and data files have always been problematic with both MSI and legacy style installers. My philosophy of deployment for such files is to treat what you install as "read-only" and then you copy them to per-user locations or set them in HKCU on application launch, using some sane process of obtaining appropriate values (from settings written to HKLM during installation, retrieved from the user, retrieved from the Internet, etc...). Please see this longer answer on the subject: Create folder and file on Current user profile, from Admin Profile. The best approach, in my opinion, is to retrieve settings on launch from an online database (as you will see if you read that linked content), but that is involved.

Answer 2

It's not clear precisely what you mean, but you cannot alter the MSI to unpack all the files in your separate CAB as if they were in the MSI as the other files are. There is too much internal data on the files inside the MSI file, in the file table, component table, and so on.

So if the CAB file is in the same location as the MSI file then you could create a custom action to copy it to the target system, and unpack if you want. The copy can be told where the MSI location is by using the [SourceDir] property or the [OriginalDatabase] property OriginalDatabase property

You'd parse that location to get the path and then do the copy to the TARGETDIR location.