PCNFSD Support for VM

PCNFSD is available on all z/VM NFS servers, and all VM/ESA NFS servers that run at least TCP/IP level 320 for VM/ESA Version 2 Release 4.0. However, the administrator can disable it. To find out if it is active, from a CMS user ID enter:


PCNFSD function is also available for TCP/IP level 310 for VM/ESA Version 2 Release 3.0 when APAR PQ16301 is applied to the NFS server code.

  • User Information

    Many NFS client implementations contain calls to PCNFSD user ID Authentication services. The purpose of these calls is to present a user ID and password to be verified by the host system. Once verified, the UID and GID by which that user is known at the host is returned to the client. For VM, the POSIXINFO and POSIXGLIST CP directory entry statements define the UID and GID(s) associated with a user ID.

    The VM implementation includes Version 1 and Version 2 of the PCNFSD protocol for the VM NFS server.

    • For TCP/IP level 3A0 for z/VM Version 3, Release 1.0 PCNFSD returns a list of supplementary GIDs to the NFS client for Version 2 and the VM NFS server makes use of the supplementary GID list when determining file permissions.

    • For earlier releases, while PCNFSD allows a list of supplementary GIDs to be returned to the NFS client for Version 2, only the VM user's primary GID (from the POSIXINFO statement) is used for subsequent NFS requests. The user's supplementary GID list (from the POSIXGLIST statment) is not used.

    Note that a value of -1 is returned for both UID and GID when the user ID is ANONYMOU.

    When PCNFSD is used, there is no need to send user ID and logon password with the NFS MOUNT or MOUNTPW. If user ID or logon password is not provide by MOUNTPW or MOUNT, the PCNFSD values are used by the NFS server, as long as the MOUNT request is received by the NFS server immediately following the PCNFSD request. The NFS client typically sends the MOUNT request immediately following the PCNFSD request. (Note that if minidisks are password-protected, the link password must still be specified in MOUNT or MOUNTPW using the password= parameter, or mdiskpw= parameter.)

    Your system administrator has the option of disabling PCNFSD for your NFS server. Contact your system administrator if you receive a message that PCNFSD is not running or is inaccessible.

    The website at http://www.vm.ibm.com/NFS provides more information about NFS mounting VM file systems.

  • System Administrator Information

    When the PCNFSD function is available on your NFS server, users may see different behavior from their NFS clients. For example, an OS/2 NFS client may prompt for a password.

    You can tailor the VMNFS CONFIG file if you wish to disable the PCNFSD function in your VM NFS server machine. The PCNFSD keyword defines whether PCNFSD is available on the VM NFS server. Specify 'PCNFSD yes' if you want the function, and 'PCNFSD no' if you do not. A sample file called VMNFS SCONFIG is shipped.

Return to the main z/VM TCP/IP NFS Server Support page.