samba - What is the meaning of these Windows Environment variables: HOMEDRIVE, HOMEPATH, HOMESHARE, USERPROFILE

Question

What is the meaning of these Windows Environment variables:

• HOMEDRIVE,
• HOMEPATH,
• HOMESHARE,
• and USERPROFILE?

Who set them? When? Who use them? For doing what?

How the configuration of the samba server modify these variables?

Answer 1

USERPROFILE is set by userenv!LoadUserProfileW which is called when, well, loading the user's profile (the HKEY_USERS<sid> hive).

• This typically happens the first time a process is started for the user.
• If you specifically arranged not to load the profile (e.g. with /noprofile for runas) then the process is run in the Default User profile which still has this variable set - since the moment it was loaded at system's startup.

HOMEDRIVE, HOMEPATH and HOMESHARE (as well as several other variables) are set by shell32!RegenerateUserEnvironment which is called on Explorer initialization¹. They are placed in the (volatile) HKCUVolatile Environment key which, being volatile, persists until the profile's unload.

• Consequently, they are only set when the user logins into their desktop session. NOT for secondary logons or services.
  • No wonder people prefer USERPROFILE nowadays.
• For HOMEPATH to be set, SYSTEM must have permissions for the profile's directory (they are initially set, of course, but may vanish when e.g. playing with Cygwin's chmod).

¹_{The code also sets a few variables that are already set by userenv. This suggests that this is an older code that persists since NT4 days. Difference between profile and home path - Server Fault confirms that.}