SCCM Gotcha: Task Sequence Media Size and FAT32

In SCCM, you have the option to create Task Sequence Media, which allows you to build a flash drive, DVD, or other bootable media that you can use to deploy operating system task sequences when no network connection is available (specifically, this is "stand-alone media" mode, versus "bootable media" and other options). This is very useful for off-site situations where you may not have any access to your organization's central network, or for computers whose NICs are not working correctly, but still need to be imaged.

In our environment, we tend to use USB flash drives for Task Sequence Media, and I was recently asked to create one for the first time with my newly-granted SCCM Administrator permissions. So, I went through the Create Task Sequence Media wizard, following the steps in the Microsoft docs, but it repeatedly failed, complaining that the USB media did not have enough space available to hold the task sequence. But that didn't make sense - I was using a 64 GB flash drive, and yet when I looked at it in the Disk Management console, I saw that it was only formatted with a single 32 GB partition.

It turns out that the reason for this is that Microsoft does not support partition sizes of greater than 32 GB on FAT32-formatted drives on anything other than Windows NT 3.51. As Wikipedia notes, FAT32 can actually support up to 8 TB or 16 TB partitions, so it's not totally clear why Microsoft chooses to impose this limit. Some conspiratorialists online claim that this was a move to force users onto Microsoft's then-new NTFS filesystem; others say that it has to do with USB flash drives' internal specifications. Whatever the reason, the fact remains that the SCCM Task Sequence Media wizard only offers to format a USB flash drive as FAT32.

This means that if you have a task sequence whose contents are near to or greater than 32 GB, you are likely to encounter the same problems I did. In our case, it is because of the vast range of hardware that our imaging drives must support, causing the driver packages to take up almost 20 GB, but in situations with a lot of software - CAD, Adobe Creative Cloud, etc. -  you could hit the limit with just one driver package.

The solution seems to be not to ask the wizard to create a bootable USB flash drive for you. Instead, choose the second option, "CD/DVD set." The default media size is 4.7GB, but you can increase this, all the way up to "unlimited." Then, using the Browse button, you select the location to which the wizard should save the resulting .ISO file, and continue through the wizard like normal. Once the .ISO is built, you can use a tool like Rufus to copy it to a USB flash drive of an appropriate size and make it bootable. Once you've confirmed that it's working, you can use another tool like ImageUSB to capture a binary copy of that flash drive, and then write it concurrently to a batch of drives.