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+:orphan:
+
+==============================================
+ ceph-dencoder -- ceph encoder/decoder utility
+==============================================
+
+.. program:: ceph-dencoder
+
+Synopsis
+========
+
+| **ceph-dencoder** [commands...]
+
+
+Description
+===========
+
+**ceph-dencoder** is a utility to encode, decode, and dump ceph data
+structures.  It is used for debugging and for testing inter-version
+compatibility.
+
+**ceph-dencoder** takes a simple list of commands and performs them
+in order.
+
+Commands
+========
+
+.. option:: version
+
+   Print the version string for the **ceph-dencoder** binary.
+
+.. option:: import <file>
+
+   Read a binary blob of encoded data from the given file.  It will be
+   placed in an in-memory buffer.
+
+.. option:: export <file>
+
+   Write the contents of the current in-memory buffer to the given
+   file.
+
+.. option:: list_types
+
+   List the data types known to this build of **ceph-dencoder**.
+
+.. option:: type <name>
+
+   Select the given type for future ``encode`` or ``decode`` operations.
+
+.. option:: skip <bytes>
+
+   Seek <bytes> into the imported file before reading data structure, use
+   this with objects that have a preamble/header before the object of interest.
+
+.. option:: decode
+
+   Decode the contents of the in-memory buffer into an instance of the
+   previously selected type.  If there is an error, report it.
+
+.. option:: encode
+
+   Encode the contents of the in-memory instance of the previously
+   selected type to the in-memory buffer.
+
+.. option:: dump_json
+
+   Print a JSON-formatted description of the in-memory object.
+
+.. option:: count_tests
+
+   Print the number of built-in test instances of the previosly
+   selected type that **ceph-dencoder** is able to generate.
+
+.. option:: select_test <n>
+
+   Select the given build-in test instance as a the in-memory instance
+   of the type.
+
+.. option:: get_features
+
+   Print the decimal value of the feature set supported by this version
+   of **ceph-dencoder**.  Each bit represents a feature.  These correspond to
+   CEPH_FEATURE_* defines in src/include/ceph_features.h.
+
+.. option:: set_features <f>
+
+   Set the feature bits provided to ``encode`` to *f*.  This allows
+   you to encode objects such that they can be understood by old
+   versions of the software (for those types that support it).
+
+Example
+=======
+
+Say you want to examine an attribute on an object stored by ``ceph-osd``.  You can do this:
+
+::
+
+    $ cd /mnt/osd.12/current/2.b_head
+    $ attr -l foo_bar_head_EFE6384B
+    Attribute "ceph.snapset" has a 31 byte value for foo_bar_head_EFE6384B
+    Attribute "ceph._" has a 195 byte value for foo_bar_head_EFE6384B
+    $ attr foo_bar_head_EFE6384B -g ceph._ -q > /tmp/a
+    $ ceph-dencoder type object_info_t import /tmp/a decode dump_json
+    { "oid": { "oid": "foo",
+          "key": "bar",
+          "snapid": -2,
+          "hash": 4024842315,
+          "max": 0},
+      "locator": { "pool": 2,
+          "preferred": -1,
+          "key": "bar"},
+      "category": "",
+      "version": "9'1",
+      "prior_version": "0'0",
+      "last_reqid": "client.4116.0:1",
+      "size": 1681,
+      "mtime": "2012-02-21 08:58:23.666639",
+      "lost": 0,
+      "wrlock_by": "unknown.0.0:0",
+      "snaps": [],
+      "truncate_seq": 0,
+      "truncate_size": 0,
+      "watchers": {}}
+
+Alternatively, perhaps you wish to dump an internal CephFS metadata object, you might
+do that like this:
+
+::
+
+   $ rados -p metadata get mds_snaptable mds_snaptable.bin
+   $ ceph-dencoder type SnapServer skip 8 import mds_snaptable.bin decode dump_json
+   { "snapserver": { "last_snap": 1,
+      "pending_noop": [],
+      "snaps": [],
+      "need_to_purge": {},
+      "pending_create": [],
+      "pending_destroy": []}} 
+
+
+Availability
+============
+
+**ceph-dencoder** is part of Ceph, a massively scalable, open-source, distributed storage system. Please
+refer to the Ceph documentation at http://ceph.com/docs for more
+information.
+
+
+See also
+========
+
+:doc:`ceph <ceph>`\(8)