TechNet describes Windows’ built-in REAgentC.exe command as able to “configure a Windows Recovery Environment (Windows RE) boot image and a push-button reset recovery image, and to administer recovery options and customizations.” The same reference goes onto observe that “You can run the command on an offline Windows image or on a running Windows operating system.” As one should expect with a command that operates on the way the OS recovers from problems with booting or running, this command must be run from an elevated command prompt (easily accessible through the Command Prompt (Admin) option in the pop-up menu that results from striking Windows Key-X in Windows 8 or 10).
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Here’s a bit of syntax by way of example that grabs information from REAgentC for use in the disk partition (diskpart) command that provides some powerful illustration of what this command can do, and why one might want to do it. The screen capture comes from my Surface Pro 3, originally purchased running Windows 8.1, and then to 10 (it’s currently running Build 10586.36).
This SP3 tablet shows the remains of two previous OSes in its listing of recovery partitions.
[Click on image to see full-size screencap]
The preceding screenshot shows how you can combine the info option for REAgentC with the diskpart command to figure out which WinRE partition your current OS is using, to see where it fits into your current disk layout. What this information tells me is that a WinRE partition for Windows 8.1 may still be hanging around (probably in partition 1) even though it’s no longer in use, that partition 5 is where the WinRE partition boots from, and that it gets its boot image from partition 6. Were one in need of extra disk space, one could use a tool like Paragon’s Hard Disk Manager Suite to recover the space that unused partitions consume, though I’d recommend a complete image backup and a known working image restore capability (which the Paragon utility also provides) before mucking about with recovery partitions of any kind. In my case, that’s only 350 MB of disk space, so it’s not worth the effort to me to get less than 0.1% of my drive space back (the drive has 230 GB of usable storage space in all).
This is a useful tool for inspecting recovery partitions to see what’s on machines under one’s management, but REAgentC.exe also supports setting the location of a WinRE boot image of one’s construction and/or choosing. It’s also suitable for working on images offline, for admins who must manage libraries or collections of such things. You can also use the command “REAgentC.exe /BootToRE” to force Windows to boot into the Recovery Environment the next time a target machine reboots.
Good stuff, and worth getting to know!