Import drive letters for use after reinstall?

Winuser said:

What I was asking is if you hadn't connected the S drive first would the first drive you connected get it's own drive letter or would it automatically be assigned the drive letter S

Click to expand...

I just repeated the experiment.
I deleted the S entry I had put in before so I was starting from scratch.
I used the .reg file to add the desired S entry.
I connected a disk it had not seen before and it was assigned F:\, the next letter in turn.
I connected the S disk and it was assigned S:\.


All the best,
Denis

hsehestedt said:

I'll have to make note of this for "bag of tricks", although I have to admit I'm not really sure if I will ever use it

Click to expand...

Hannes,

I felt the same until I realised it could be used to save the current configuration.

I have exported the Registry Key and deleted all the non-"\\DosDevices\\ entries so I have a restoration file [it is so tedious working with that exported key]. I have also deleted all entries related to internal disks.
I do use the same assignments on all my computers so the .reg can be used on them all.

I'm having a stab at a script for extracting the relevant values and writing them into a Reg Add script for restoration.
I have the feeling that it won't work.
And it's late and I'm tired.


All the best,
Denis

So you'll get something in the pattern of my post #32.

Click to expand...

OK, thank you very much!

Donk said:

OK, thank you very much!

Click to expand...

Do delete all lines related to disks other than those external disks you asked about.
The file you create will have an entry for C:\ but Windows creates that for the particular hardware of that computer.
In my own file, I have deleted the lines for C:\, D:\ & M:\ because these are always disks / partitions on the particular computer concerned. I accept that I'll manually set up D:\ & M:\ after a Windows installation.


Denis

That's good point, so I would also delete some of those lines, I have two or three partitions on internal drive C:, yes, maybe better to assign the letters manually.

And I would do the registry mess immediately after an installation, if I completely would destroy the registry I just could install Win again. Respectively I would make a backup of the reg before.

Many thanks!

Yes, I expected it would be fine. I used to back up the key in winpe then restore it after macrium had screwed them up. I dont bother with that in winpe now, I just reset the shortcuts instead.

This script writes a batch file that can be run, with Admin approval, to restore the current external disk drive letter assignments.
I selected my approach to the job for these reasons
- the hardware used for external disks will change from time to time so the job will need to be done more than once, and
- running this script will be less work than editing an export of that Registry key, and
- using Reg Add commands is less work than running ["merging"] an exported Registry key.
The backing up script runs without any need for elevation.
The output file RestoreAssignedDrives.bat needs Admin approval to run because it writes to HKLM.
BackupAssignedDriveLetters.bat [attached]
:: This script backs up external drive letter assignments into a script file for writing them back into the Registry
:: My list of assignments to skip backing up for, the lines beginning If "%ThisLine:~0,13%", account for all my internal drives because it would be inappropriate to restore their drive letters to different computers [as I intend to do].
:: The output file is re-written every time this script is run.
:: Written by Denis, Try3
:: This script was originally posted in www.elevenforum.com/t/import-drive-letters-for-use-after-reinstall.22267

:: Alter the prompt to help see commands and their responses clearly
prompt $g
:: Some people like adding an @echo off command but I don't.
:: - The script does not take so long to run that I would ever feel any benefit from the time saved in execution by using @echo off.
:: - I run scripts such as these minimised so I would not benefit from hiding anything
:: - I would have to cancel the @echo off & run that modified version of the script if I needed to debug the script
:: - As it stands, if I wanted to debug then I would re-add the leading :: from the final line of this script [which I've left in for the time being but will remove when testing is complete]

:JustGetOnWithIt
:: Set up output
:: I will use a protected script folder because the output is an active object
:: I have tested that the output path can include spaces and special characters such as ampersands.
Set "OutputFolder=%~dp0"
:: Remove trailing \ from OutputFolder [swapping around values during testing can often lead me to mistakes in this regard]
If "%OutputFolder:~-1%"=="\" Set OutputFolder=%OutputFolder:~0,-1%
Set "OutputFile=%OutputFolder%\RestoreAssignedDrives.bat"

:: Write the preamble in the output file
echo ::This script restores the backed up drive letter assignments for external disks>"%OutputFile%"
echo ::This script must be run as Admin because it writes entries to HKLM>>"%OutputFile%"
echo :: Written by Denis, Try3 TenForums, ElevenForum, TwelveForums>>"%OutputFile%"
echo :: The parent script was originally posted in www.elevenforum.com/t/import-drive-letters-for-use-after-reinstall.22267>>"%OutputFile%"

:: Read each line of the Registry Key
For /F "tokens=*" %%A in ('Reg Query "HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices" ') Do Call :ProcessEachLine "%%A"
GoTo Endex

:ProcessEachLine
:: This subroutine reads each line of the Registry Key
Set "ThisLine=%~1"
:: Escape if a blank line has been passed [I have not checked that that cannot happen and it's easyto assume it can]
If "FF%ThisLine%FF"=="FFFF" GoTo :EOF
:: Escape for all non-relevant lines in this huge Registry Key
If Not "%ThisLine:~0,12%"=="\DosDevices\" GoTo :EOF
::::: Put in escapes for internal drives C D E F M
::::: My method of escaping F:\ for the sake of the one computer that has an internal disk F:\ means that I will not backup any F:\ drive letter assignments from any computer but that's fine as I never use any
::::: If I backed them up I would have to insert a ComputerName-dependent escape into the restoration script anyway so I might as well keep it simple
If "%ThisLine:~0,13%"=="\DosDevices\C" GoTo :EOF
If "%ThisLine:~0,13%"=="\DosDevices\D" GoTo :EOF
If "%ThisLine:~0,13%"=="\DosDevices\E" GoTo :EOF
If "%ThisLine:~0,13%"=="\DosDevices\F" GoTo :EOF
If "%ThisLine:~0,13%"=="\DosDevices\M" GoTo :EOF

:: Write each relevant line, each drive letter assignemnt to be restored, into the output file
:: Lines extracted from the Registry key are in the pattern \DosDevices\S: REG_BINARY 444D494F3A49443A6C973A17EA6A53469D66AAAC5B339B57
:: Required syntax for the Reg Add command that does the restoration Reg Add HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices /v \DosDevices\S: /t REG_BINARY /d 444D494F3A49443A6C973A17EA6A53469D66AAAC5B339B57
echo Reg Add HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices /v %ThisLine:~0,14% /t REG_BINARY /d %ThisLine:~31%>>"%OutputFile%"

GoTo :EOF

:Endex
:: Pause at end during testing


A shortened example of its output, RestoreAssignedDrives.bat, is
::This script restores the backed up drive letter assignments for external disks
::This script must be run as Admin because it writes entries to HKLM
:: Written by Denis, Try3 TenForums, ElevenForum, TwelveForums
:: The parent script was originally posted in www.elevenforum.com/t/import-drive-letters-for-use-after-reinstall.22267
Reg Add HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices /v \DosDevices\S: /t REG_BINARY /d 444D494F3A49443A6C973A17EA6A53469D66AAAC5B339B57

I have tested
BackupAssignedDriveLetters.bat
RestoreAssignedDrives.bat
and they work.

I had intended to include a self-elevating code block in RestoreAssignedDrives.bat but am having trouble getting it to work [I last worked on this topic four years ago and it's difficult getting back into the right frame of mind to understand the notes I kept about it]. My problem is writing that code block into the output file in a manner that survives elevation.


Denis

Try3 said:

I just repeated the experiment.
I deleted the S entry I had put in before so I was starting from scratch.
I used the .reg file to add the desired S entry.
I connected a disk it had not seen before and it was assigned F:\, the next letter in turn.
I connected the S disk and it was assigned S:\.


All the best,
Denis

Click to expand...

Thanks for doing the test to see if it actually does keep the drive letter assigned to the original drive or not. I do have a few USB drives I always want to be the same drive letter. The drives I use for my system images and the drives I use for my media content as an example. Knowing this reg hack may come in handy for me when I replace one or more of my computers in the future.

I have a lot of data and I move a lot of data from drive to drive. Ever since I installed Windows 11 on my PC I've had trouble keeping all my drives in order. Admittedly, I have a number of hard drives but before Windows 11 was installed on this unit they kept themselves in alphabetical order in Disk Management and stayed that way. Even Windows 7 kept them in their proper alphabetical order. My friend thinks I'm being OCD about this but it does help to read what's what quickly and efficiently when transferring data. Order isn't necessarily a bad thing, especially when one is using a considerable number of drives.

Try3 said:

I had intended to include a self-elevating code block in RestoreAssignedDrives.bat but am having trouble getting it to work

Click to expand...

I solved my problem with this and can now include self-elevation in the output script RestoreAssignedDrives.bat [which needs elevation because it writes to HKLM].
I've also added self-elevation in BackupAssignedDriveLetters.bat because I am going to write the output file, RestoreAssignedDrives.bat, in a protected folder [as I do for all my scripts].


Denis

The more I consider my script, the more problems I find.
- As a tool to use on a new installation, it seems fine.
- As a tool to use to restore a configuration to an existing installation, it has serious shortcomings in that a saved configuration with a specific disk as H:\ could be restored after I had changed setup & made that disk, say, U:\. So my tool could result in that disk being assigned as both H:\ & U:\ which would cause unknown problems. I think the restoration process would have to start by removing all existing external disk drive letter assignments.

I can see how I might handle that.
But then I might identify further shortcomings.
I don't know if the game is worth the candle.


Denis

one possibilty could be could use a similar method to delete the dosdevices except for the os .Your processeachline could escape the os entry and reg delete the others

Yes, I can do that [I've already considered how best to do it] but the user will have to list the drive letters of all internal fixed disks & partitions so that they can be skipped over.
Once armed with that list, I could readily ensure that all other drive letters are removed before then restoring those generated by the backup script.
- Windows does not list fixed disk & partitions for us unfortunately.
- It will list "removable" disks but it only includes SD cards & USB sticks in that category not external HDDs-SSDs.
- I have been unable to derive any list of fixed disks or any list of external disks.


All the best,
Denis

but the user will have to list the drive letters of all internal fixed disks & partitions so that they can be skipped over.

Click to expand...

1. Not sure why. If the restore script derived from the previous installation has those entries should work fine deleting current dosdevices (except os ) then restore from that script.

2. For many people they would only want to escape the os entry when backing up the original dosdevice entries. Then after reinstall delete the new dosdevices ( except os) and restore the rest.

3. Your desire to exclude H and a few others is a bit unusual.

It is more complicated for people who use different osletters for their various installations. Not everybody is addicted to using C as the osletter but that is also unusual. For example an enthusiast could be triple booting. The first os has letter c, the second os has letter d and the third os has letter e. Some enthusiats do that kind of thing.

For the average punter paragraph 2 should do the job.

SIW2 said:

If the restore script derived from the previous installation has those entries

Click to expand...

The user has to list the drive letters of internal fixed disks.
No list of them exists anywhere.

I know which are internal drives and which are not.
- This is the response to fsutil fsinfo drives C:\ D:\ E:\ F:\ K:\ M:\ T:\ V:\
- echo.list vol | DiskPart | find /i "Removable" will correctly identify F:\ & T:\ as removable.
- Nothing will report that K:\ is an external HDD/SSD.
I can write the list in the backup script and can carry it over into the restoration script.
Nobody can do that for me.

Denis

Why?

I ran your script after commenting out these


the backup script looks ok

It has included the fixed, removable and usb dosdevice entries as far as I can see.

then to delete current dosdevs after reinstall ( except os ) something like this:



this is the output. looks ok.

I do not want to alter existing drive letters for fixed internal drives.
If, for example, you had run your amended version on my computer then removing M:\ would cause half an hours remedial work.
It's that need for user intervention that I hoped I'd be able to avoid but cannot.


All the best,
Denis

Try3 said:

I had intended to include a self-elevating code block in RestoreAssignedDrives.bat but am having trouble getting it to work

Click to expand...

Nice work! This is what I use to self-elevate my batch files:

hsehestedt said:

Nice work

Click to expand...

Hannes,

Well, it's nice of you to say so but I think the script is not [yet] worthwhile in a running system that needs its external disk letters restored to those first set up.
What it needs is an intervention that seeks a list of those drive letters not to interfere with so that all others can be removed prior to the restoration [because prior removal is required to avoid attempting to set multiple drive letters for the same hardware].
That intervention is what I had hoped to avoid but cannot.
Only the user can know which drive letters to avoid removing-restoring in order to avoid disrupting Windows

I can generate the list CDEFKMTV during the backup procedure and present it to the user early in the restoration procedure [probably in a vbs InputBox] for the user to remove or even add entries.
I had hoped not to need to do this but, as I say, it is unavoidable because nobody else knows the significance of any particular drive letter. Even C:\ has been known to vary [it's almost a decade since I've seen Windows 10 install itself to the drive letter F:\ and the very few reports by others also indicates its rarity - I wish now that I'd made a screenshot of it].

Incidentally, I use a very slightly different self-elevation method and one is pretty much as good as any other but I always combine mine with an ampersand check because no self-elevation method I have tried can work correctly with the batch file in a path that contains an ampersand.
Set "ThisPath=%~dp0"
If Not "%ThisPath:&=%"=="%ThisPath%" ((cls) & (Title ERROR) & (Echo This procedure cannot be used with the batch file in a path containing an ampersand. Move the batch file to a different location before running it again.) & (Pause) & (GoTo Endex))
reg query "HKU\S-1-5-19" >nul ||(PowerShell start """%~dpnx0""" -verb RunAs & Exit /B)

:Endex
pause at Endex during testing
If there's an ampersand in the path, the command
PowerShell start """%~dpnx0""" -verb RunAs
fails. I've tried the variations I would normally think of for coping with & but have not found a solution.


All the best,
Denis

Even C:\ has been known to vary

Click to expand...

could include some error checking something like this

reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion" /v PathName > tmpoutfile.out
if ERRORLEVEL 1 (
echo Failed to get current OS letter from registry.
goto :wherever
)