Linux samba server: cifs_mount failed w/return code = -12

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This is an oldie, but considering it’s unanswered and I was looking into IPC$ and Samba, I will give it a try for the sake of documentation.

Why would smbd not clean up IPC$ shares?

As stated above in the comments to your question, the service is used for remote administration and communication among servers, and particularly in Samba it’s used for some browsing and tcp/ip purposes. Unless you need it for some reason or something doesn’t work, it’s safe to disable it. [1]

Why establish one IPC$ per user connection to a share rather than one
per client connection?

Because a user can have multiple client connections.

Can you disable IPC$ share creation from the client side?

Yes and no. It doesn’t really disable the creation of the IPC$ share, but you can disable access to it from the windows client.[2]

For windows Vista, Windows 7, Windows 8 and Windows 10, you can do the following registry edit:

  1. Click Start, type “regedit” in the Search box, and then click regedit.exe in the search results. The User Account Control dialog box appears.
  2. Say “Yes” to the UAC prompt and the Registry Editor should open.
  3. Open the HKEY_LOCAL_MACHINE branch.
  4. Open the SYSTEM branch.
  5. Open the CurrentControlSet branch.
  6. Open the Services branch.
  7. Open the LanmanServer branch.
  8. Select the Parameters branch.
  9. Select Edit, New, “DWORD (32-bit) Value”
  10. Type “AutoShareWks” and press Enter. (Leave the default value of 0.)
  11. Reboot or restart the service using a Command Prompt (DOS or terminal): “net stop server” then “net start server”.

Is there a way to increase the max # connections per share (not that
this would have helped in this case)? I didn’t see it in the docs.

Yes[3]. Below the share just input:

[share]
   max connections = ##

Where XX is the number of connections.

Sources:

  • [1] https://www.samba.org/samba/docs/old/Samba3-HOWTO/securing-samba.html
  • [2] https://www.petri.com/disable_administrative_shares
  • [2] https://www.weavweb.net/2015/08/27/disabling-hidden-shares-in-windows-10-windows-vista-windows-7-and-windows-8-1/
  • [2] https://support.microsoft.com/en-us/help/954422/how-to-remove-administrative-shares-in-windows-server-2008
  • [3] https://www.samba.org/samba/docs/using_samba/ch09.html

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