z/VM's NFS Client Support - Hints and Tips

  • Supported Services
    Use the rpcinfo -p hostname command to see which services are available at the host. You need to see mountd and nfs in the list, and having pcnfsd makes life much easier, although you can live without it.

  • Export list
    Some systems, such as AIX and LINUX, require you to define which directories can be mounted. This is called an export list. For AIX and LINUX, this is contained in the /etc/exports file, which usually requires root authority to edit. You may need to contact the system administrator to add entries to the export list.

    Use the openvm showmount hostname (export command to see which directories are exported.

    If the export list contains an entry allowing you to mount but you get a permission error on OPENVM MOUNT it may be because the target NFS server requires the use of a low port number (in the range 0 to 1023). (This is commonly the default on LINUX systems, for example.) Contact the System Administrator for the remote host to ask that the NFS server configuration be changed to permit clients to use any port number. The System Administrator should consult the NFS server documentation to determine how this is done. The documentation may make reference to "secure" or "insecure" port numbers.

    Alternatively, you can use the LOCALPORT option on the mount to force the NFS client to use a low port number. Using LOCALPORT may require additional configuration as the z/VM TCP/IP stack restricts all "Well-Known" ports (ports 1-1023) from general use on a default basis. You may need to configure specific port reservations via the PORT statement in PROFILE TCPIP.

  • Specifying username for remote host
    When the pcnfsd service is available, you can specify a username on the OPENVM MOUNT command which indicates how you want to be known at the remote host. You can provide a shortcut for this by creating entries in the NETRC DATA file for each remote host.

    machine hostname login username password password

    This uses the PC-NFS protocol, so you will receive an error if the target NFS server does not support PC-NFS.

  • NFS server options
    Some NFS servers, such as VM's and OS/390's, allow you to specify options for the NFS server. Serveroptions can be included in the NFS pathname on the OPENVM MOUNT command. Use the NFS server documentation for the target platform to decide whether serveroptions are needed.

    openvm mount /../nfs:host/dirname,serveroptions nfssubdir

  • EBCDIC/ASCII Translation
    The default behavior for VM's NFS client is to translate data files into ASCII and to bypass translation for executable files. VMFILETYPE statements in the TCPIP DATA file define which files are translated. For example, files with an extension of .html are translated, while files with an extension of .bin are not.

    By default, data translation uses the POSIX translation table, POSIX TCPXLBIN.

    Is the remote host running VM or OS/390? If so, you can eliminate the overhead of data translation.

    • Use the NOTRANSLATE option on OPENVM MOUNT to tell the NFS Client not to translate text files into ASCII.
    • Use the trans=no VM NFS server option to tell the VM NFS server not to translate text files from ASCII to EBCDIC.

  • Line end processing
    You may need to tell CMS which line end characters to use to XEDIT or OPENVM GET a file in an NFS-mounted file system. Some remote systems use CRLF, some use LF, and some use NL. Specify this using the BFSLINE option.