plucky (1) nbdkit-exportname-filter.1.gz

NAME

       nbdkit-exportname-filter - adjust export names between client and plugin

SYNOPSIS

        nbdkit --filter=exportname plugin [default-export=NAME]
         [exportname-list=MODE] [exportname-strict=true] [exportname=NAME]...
         [exportdesc=DESC]

DESCRIPTION

       Some plugins (such as nbdkit-file-plugin(1) and filters (such as nbdkit-ext2-filter(1) are able to serve
       different content based on the export name requested by the client.  The NBD protocol allows a server to
       advertise the set of export names it is serving.  However, the list advertised (or absent) from the
       plugin may not always match what you want an actual client to see.  This filter can be used to alter the
       advertised list, as well as configuring which export should be treated as the default when the client
       requests the empty string ("") as an export name.

PARAMETERS

       default-export=NAME
           When the client requests the default export name (""), request the export "NAME" from the underlying
           plugin instead of relying on the plugin's choice of default export.  Setting NAME to the empty string
           has the same effect as omitting this parameter.

       exportname-list=keep
       exportname-list=error
       exportname-list=empty
       exportname-list=defaultonly
       exportname-list=explicit
           This parameter determines which exports are advertised to a guest that requests a listing via
           "NBD_OPT_LIST".  The default mode is "keep" to advertise whatever the underlying plugin reports.
           Mode "error" causes clients to see an error rather than an export list.  Mode "empty" returns an
           empty list.  Mode "defaultonly" returns a list that contains only the canonical name of the default
           export.  Mode "explicit" returns only the exports set by "exportname=".  Note that the list of
           advertised exports need not reflect reality: an advertised name may be rejected, or a client may
           connect to an export name that was not advertised, but learned through other means.

       exportname-strict=false
       exportname-strict=true
           Normally, a client can pass whatever export name it wants, regardless of whether that name is
           advertised.  But setting this parameter to true will cause the connection to fail if a client
           requests an export name that was not included via an exportname= parameter.  At this time, it is not
           possible to restrict a client to exports advertised by the plugin without repeating that list via
           exportname; this technical limitation may be lifted in the future.

       exportname=NAME
           This parameter adds "NAME" to the list of advertised exports; it may be set multiple times.

       exportdesc=keep
       exportdesc=none
       exportdesc=fixed:STRING
       exportdesc=script:SCRIPT
           The "exportdesc" parameter controls what optional descriptions are sent alongside an export name.  If
           set to "keep" (the default), descriptions are determined by the plugin.  If set to "none",
           descriptions from the plugin are ignored (useful if you are worried about a potential information
           leak).  If set to "fixed:STRING", the same fixed string description is offered for every export.  If
           set to "script:SCRIPT", this filter executes script with $name set to the export to be described, and
           uses the output of that command as the description.

EXAMPLES

       Suppose that the directory /path/to/dir contains permanent files named file1, file2, and file3.  The
       following commands show various ways to alter the use of export names while serving that directory:

       Allow a client requesting "" to get the contents of file2, rather than an error:

        nbdkit --filter=exportname file dir=/path/to/dir default-export=file2

       Do not advertise any exports; a client must know in advance what export names to try:

        nbdkit --filter=exportname file dir=/path/to/dir exportname-list=empty

       Allow clients to connect to file1 and file3, but not file2:

        nbdkit --filter=exportname file dir=/path/to/dir \
          exportname-list=explicit exportname-strict=true \
          exportname=file1 exportname=file3

       Offer ls(3) long descriptions alongside each export name:

        nbdkit --filter=exportname file dir=/path/to/dir \
          exportdesc=script:'ls -l /path/to/dir/"$name"'

FILES

       $filterdir/nbdkit-exportname-filter.so
           The filter.

           Use "nbdkit --dump-config" to find the location of $filterdir.

VERSION

       "nbdkit-exportname-filter" first appeared in nbdkit 1.24.

SEE ALSO

       nbdkit(1), nbdkit-filter(3), nbdkit-ext2-filter(1), nbdkit-extentlist-filter(1), nbdkit-fua-filter(1),
       nbdkit-nocache-filter(1), nbdkit-noparallel-filter(1), nbdkit-nozero-filter(1), nbdkit-file-plugin(1),
       nbdkit-info-plugin(1).

AUTHORS

       Eric Blake

COPYRIGHT

       Copyright Red Hat

LICENSE

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       •   Neither the name of Red Hat nor the names of its contributors may be used to endorse or promote
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