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================
CephFS Snapshots
================
CephFS snapshots create an immutable view of the file system at the point
in time they are taken. CephFS support snapshots which is managed in a
special hidden subdirectory named ``.snap`` .Snapshots are created using
``mkdir`` inside this directory.
Snapshots can be exposed with a different name by changing the following client configurations.
- ``snapdirname`` which is a mount option for kernel clients
- ``client_snapdir`` which is a mount option for ceph-fuse.
Snapshot Creation
==================
CephFS snapshot feature is enabled by default on new file systems. To enable
it on existing file systems, use the command below.
.. code-block:: bash
$ ceph fs set <fs_name> allow_new_snaps true
When snapshots are enabled, all directories in CephFS will have a special ``.snap``
directory. (You may configure a different name with the client snapdir setting if
you wish.)
To create a CephFS snapshot, create a subdirectory under ``.snap`` with a name of
your choice.
For example, to create a snapshot on directory ``/file1/``, invoke ``mkdir /file1/.snap/snapshot-name``
.. code-block:: bash
$ touch file1
$ cd .snap
$ mkdir my_snapshot
Using snapshot to recover data
===============================
Snapshots can also be used to recover some deleted files.
- ``create a file1 and create snapshot snap1``
.. code-block:: bash
$ touch /mnt/cephfs/file1
$ cd .snap
$ mkdir snap1
- ``create a file2 and create snapshot snap2``
.. code-block:: bash
$ touch /mnt/cephfs/file2
$ cd .snap
$ mkdir snap2
- ``delete file1 and create a new snapshot snap3``
.. code-block:: bash
$ rm /mnt/cephfs/file1
$ cd .snap
$ mkdir snap3
- ``recover file1 using snapshot snap2 using cp command``
.. code-block:: bash
$ cd .snap
$ cd snap2
$ cp file1 /mnt/cephfs/
Snapshot Deletion
==================
Snapshots are deleted by invoking ``rmdir`` on the ``.snap`` directory they are
rooted in. (Attempts to delete a directory which roots the snapshots will fail;
you must delete the snapshots first.)
.. code-block:: bash
$ cd .snap
$ rmdir my_snapshot
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