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ERROR_SUBST_TO_JOIN
What ERROR_SUBST_TO_JOIN means
ERROR_SUBST_TO_JOIN is a Win32 system result whose documented message is: “The system tried to SUBST a drive to a directory on a joined drive.” In practical troubleshooting, it belongs to legacy mapping rules that prohibit creating a SUBST drive whose target lies on a joined drive.
Typical causes
- the selected target path is exposed through a JOIN mapping
- a script sees only the logical path and misses the underlying topology
- configuration was generated on a system without the same JOIN state
How to investigate the result
- resolve the target directory to its underlying drive
- enumerate JOIN mappings before running SUBST
- Compare path resolution under the user and service accounts
Developer guidance
Point SUBST directly at a canonical directory on a normal drive and perform mapping-state validation before creation.
Administrator and support guidance
Remove unnecessary JOIN dependencies or select a target outside the joined namespace. Test logon scripts in a clean session.
Example
A compatibility script maps R: to a directory that is visible only through an existing JOIN, and Windows returns this result.
How it differs from related results
It is the mirror of ERROR_JOIN_TO_SUBST and identifies the direction of the unsupported mapping combination.
References
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