Event ID 1023 — Subsystem for UNIX-based Applications Functionality

Applies To: Windows Server 2008

Subsystem for UNIX-based Applications (SUA) Functionality is a measure of how the SUA send-and-receive utility, Psxss.exe, is functioning. When Psxss.exe is operating normally, SUA is able to accept user commands, and port applications over to Windows-based operating systems from UNIX-based operating systems.

Event Details

Product: Windows Subsystem for UNIX-based Applications
ID: 1023
Source: Microsoft-Windows-SUA-Psxss
Version: 6.0
Message: Could not connect to Mapping Server at host %1: Host name resolution failed while connecting.


Check mapping server

SUA was unable to resolve the name of the Network File Service (NFS) mapping server. SUA might not have access to NFS files or folders because the program cannot map the identity of one or more UNIX-based host computers.

To check the mapping server:

  1. Open Registry Editor.
    • Click Start, type regedit in the Start Search text box, and then press Enter.
  2. Locate the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSNFS\MappingServers.
  3. Double-click the registry key to view its properties. Copy the server name or IP address provided in the registry key.
  4. In a Command Prompt window, ping the mapping server.
    • To open a Command Prompt window, click Start, and then either click Command Prompt on the Start menu, or type cmd in the Start Search text box, and then press Enter.
  5. If pinging the server is successful, and the server name in the registry key is a network and path name instead of an IP address, replace the value in the registry key with the server's IP address, obtained in the ping response. Save your changes, close Registry Editor, and then restart the computer that logged the error.
  6. If pinging the mapping server fails, verify that the mapping server is operational, and that it has been correctly configured in accordance with procedures in the Server for Network File Services Help.
    • You can learn more about configuring User Name Mapping by entering nfsadmin /? in a Command Prompt window on a computer that is running the Services for Network File System role service of the File Services role.


Verify that the Subsystem for UNIX-based Applications (SUA) Psxss.exe utility is functioning, first by viewing Psxss.exe in the Windows Task Manager, and then by using an SUA application that you have developed or are porting to Windows to transmit data over the network.

To verify that Psxss.exe is running:

  1. Open Windows Task Manager by pressing CTRL+ALT+DEL, and then clicking Task Manager.
  2. On the Processes tab, select the Show processes from all users check box.
  3. Verify that PSXSS.exe is running.

Next, use an application on which you are working in SUA, or that you are porting to Windows by using SUA, to send some data over the network. For example, attempt to use your application to modify files or documents in another location on the network. If PSXSS.exe is functioning properly, and is active in the list of processes in Task Manager, sending SUA application data over the network should succeed.

Subsystem for UNIX-based Applications Functionality

Subsystem for UNIX-based Applications