Games - NTFS junction point

Home > Listing Index > Games > NTFS junction point

	Games - NTFS junction point

In computing, an NTFS junction point (JP) is a type of NTFS reparse point in the NTFS file system. It requires NTFS on-disk version 3.0 or later, which can be created (or converted from a FAT partition) using Windows 2000 and later (e.g. Windows XP) Windows operating systems (technically Windows 2000 is NT 5, which explains the 5.0 version of the filesystem driver file ntfs.sys, but the file system version it creates is 3.0. Windows XP's native NTFS version is 3.1, while the ntfs.sys filesystem driver version is 5.1 - the NT version number of XP). Junction Points can be used in a similar way to symbolic links - allowing you to create a link to a folder that is, for most intents and purposes, the same as the folder itself. This has many benefits over a Windows shell shortcut (.lnk) file, such as allowing you to access files within the shortcut via explorer, the console, etc.

Note: junction points link only to folders (*). You can create a similar link to a file, but with the restriction that the file must belong to the same logical volume, use hard links.

(*) This isn't 100% correct, as you can also use it to point to e.g. devices for removable media, or other filesystem partitions, and in early incarnations you could even use it to access (already authenticated) SMB shares. Unfortunately, that latter part of it was not too well though out and/or designed, why the behaviour changes depending on even service-pack levels, but that's another story.

Warning

NOTE: Microsoft
strongly recommends:
*Use NTFS
ACLs
to protect junction points from inadvertent deletion.
*Use NTFS ACLs to protect files and directories targeted by junction points from inadvertent deletion or other file system operations.
*Never delete a junction point using Explorer, a del /s command, or other file system utilities that walk recursively into directory trees. These utilities will affect the target directory and all subdirectories. Instead, use the utilities described below to delete junction points.
*Use caution when applying ACLs or changing file compression in a directory tree that includes NTFS Junction Points.
*Do not create namespace cycles with NTFS or DFS junction points.
*Place all your junction points at a secure location in a namespace where you can test them out in safety, and other users will not mistakenly delete them or walk through them.
Obscure: There are issues relating to junction points on Win2000 domain controllers & certain Active Directory files. See for more details.

Examples of use

Program redirection

:By setting a JP that points to a directory containing a particular version of a piece of software, you can, in most cases, seemlessly add another version of the software and redirect the JP to point to the version you wish to use.

Space saving

:If you are running out of space on a drive, you can move those files to a new drive - but this can cause some problems with old links, configuration files, registry, etc. By creating a JP at the previous location (pointing to the new location) windows will treat it the same as if the directory still exists there, redistributing the load to the filesystem with more space.

Observed effects

WinXP Pro

Explorer

Deleting a JP using explorer is not safe - it will delete the targeted files immediately if using shift-delete.
Beware: if the JP is sent to the recycle bin, the targeted files will look safe, but will be deleted when the recycle bin is emptied.
Moving the JP to a different location on the same drive only moves the JP, however moving to another drive turns the JP into a normal folder and moves all files there (leaving the targeted directory empty).
Whilst walking through the directory with explorer, it seems impossible to delete folders, however files can be deleted.
A solution for these issues is installing NTFS Link (see external links section), which makes sure that the Explorer handles junctions correctly. One can also use the fsutil application to delete and query reparse points (administration privileges are required).

Console

(command prompt - cmd.exe)

The dir command in Windows 2000 or later recognizes junction points, displaying instead of in directory listings.
Any commands that would normally affect files inside a normal directory will act the same here, so don't use del myjunction - this will just delete all the files in the targeted folder.
rmdir & move seem to work fine with junctions, with the caveat that move won't let you move the junction to another volume (as opposed to Windows explorer, as mentioned above.)
rmdir seems safe in that it only deletes the JP, not the targeted files.
Whilst walking through the directory with the console, files can be deleted, but unlike explorer, directories can also be deleted (using rmdir /s dirname for example.)

[ Visit the complete Wikipedia entry for NTFS junction point ]

Searches on eBay

ntfs junction point