How in the Tech

Keeping subst mounts across Windows reboots

By Adam Myers ⋅ August 19, 2009 ⋅ Tags: Command Prompt, System Administration

Longtime PC users may be familiar with the DOS command subst – short for substitute. For those unfamiliar, subst allows you to substitute a physical folder path with a virtual drive. As an example, you could map the path of your iTunes Music folder from c:\Users\username\Music\iTunes\iTunes Music to the virtual drive M. Then under My Computer, you would see your traditional C drive as well as a virtual drive M. You may already see some potential applications for this; in my situation here it allows me to have a consistent iTunes Library mapping across different computers where I may not have the same username. iTunes is told to look on M drive for all my music.

This is all well and good but there is one rather large and frustration catch, subst commands do not stick after a reboot – you must repeat the process each time. This truly cuts into the usefulness of subst, at least to me. Thankfully, there is a solution!

Psubst is a free utility that address that little problem above, perhaps you can already guess what the p stands for? Persistent subst utilizes the exact same syntax as the native subst command complete with the somewhat dated process of launching a Command window to execute.

1. Download psubst from the link above and extract the files into a folder within your PATH – I suggest c:\windows\system32. The advantage of putting the program in your PATH means you don’t have to type the full folder path when running the program.
2. Launch a Command Prompt with WIN+R and typing cmd.
3. To create a virtual disk use the syntax psubst <virtual drive> <physical drive>:/path from inside the Command Prompt. Deleting the virtual drive can be accomplished with psubst <virtual drive> /D while just psubst will list all the virtual drives.
4. To make the virtual drive persistent across reboots simply append the flag /P. Using my situation from above the command I would use is: psubst m: “c:\users\username\Music\iTunes\iTunes Music” /P.