ceph/doc/ceph-volume/simple/scan.rst

   1 .. _ceph-volume-simple-scan:
   2
   3 ``scan``
   4 ========
   5 Scanning allows to capture any important details from an already-deployed OSD
   6 so that ``ceph-volume`` can manage it without the need of any other startup
   7 workflows or tools (like ``udev`` or ``ceph-disk``). Encryption with LUKS or
   8 PLAIN formats is fully supported.
   9
  10 The command has the ability to inspect a running OSD, by inspecting the
  11 directory where the OSD data is stored, or by consuming the data partition.
  12
  13 Once scanned, information will (by default) persist the metadata as JSON in
  14 a file in ``/etc/ceph/osd``. This ``JSON`` file will use the naming convention
  15 of: ``{OSD ID}-{OSD FSID}.json``. An OSD with an id of 1, and an FSID like
  16 ``86ebd829-1405-43d3-8fd6-4cbc9b6ecf96`` the absolute path of the file would
  17 be::
  18
  19     /etc/ceph/osd/1-86ebd829-1405-43d3-8fd6-4cbc9b6ecf96.json
  20
  21 The ``scan`` subcommand will refuse to write to this file if it already exists.
  22 If overwriting the contents is needed, the ``--force`` flag must be used::
  23
  24     ceph-volume simple scan --force {path}
  25
  26 If there is no need to persist the ``JSON`` metadata, there is support to send
  27 the contents to ``stdout`` (no file will be written)::
  28
  29     ceph-volume simple scan --stdout {path}
  30
  31
  32 .. _ceph-volume-simple-scan-directory:
  33
  34 Directory scan
  35 --------------
  36 The directory scan will capture OSD file contents from interesting files. There
  37 are a few files that must exist in order to have a successful scan:
  38
  39 * ``ceph_fsid``
  40 * ``fsid``
  41 * ``keyring``
  42 * ``ready``
  43 * ``type``
  44 * ``whoami``
  45
  46 If the OSD is encrypted, it will additionally add the following keys:
  47
  48 * ``encrypted``
  49 * ``encryption_type``
  50 * ``lockbox_keyring``
  51
  52 In the case of any other file, as long as it is not a binary or a directory, it
  53 will also get captured and persisted as part of the JSON object.
  54
  55 The convention for the keys in the JSON object is that any file name will be
  56 a key, and its contents will be its value. If the contents are a single line
  57 (like in the case of the ``whoami``) the contents are trimmed, and the newline
  58 is dropped. For example with an OSD with an id of 1, this is how the JSON entry
  59 would look like::
  60
  61     "whoami": "1",
  62
  63 For files that may have more than one line, the contents are left as-is, except
  64 for keyrings which are treated specially and parsed to extract the keyring. For
  65 example, a ``keyring`` that gets read as::
  66
  67     [osd.1]\n\tkey = AQBBJ/dZp57NIBAAtnuQS9WOS0hnLVe0rZnE6Q==\n
  68
  69 Would get stored as::
  70
  71     "keyring": "AQBBJ/dZp57NIBAAtnuQS9WOS0hnLVe0rZnE6Q==",
  72
  73
  74 For a directory like ``/var/lib/ceph/osd/ceph-1``, the command could look
  75 like::
  76
  77     ceph-volume simple scan /var/lib/ceph/osd/ceph1
  78
  79
  80 .. _ceph-volume-simple-scan-device:
  81
  82 Device scan
  83 -----------
  84 When an OSD directory is not available (OSD is not running, or device is not
  85 mounted) the ``scan`` command is able to introspect the device to capture
  86 required data. Just like :ref:`ceph-volume-simple-scan-directory`, it would
  87 still require a few files present. This means that the device to be scanned
  88 **must be** the data partition of the OSD.
  89
  90 As long as the data partition of the OSD is being passed in as an argument, the
  91 sub-command can scan its contents.
  92
  93 In the case where the device is already mounted, the tool can detect this
  94 scenario and capture file contents from that directory.
  95
  96 If the device is not mounted, a temporary directory will be created, and the
  97 device will be mounted temporarily just for scanning the contents. Once
  98 contents are scanned, the device will be unmounted.
  99
 100 For a device like ``/dev/sda1`` which **must** be a data partition, the command
 101 could look like::
 102
 103     ceph-volume simple scan /dev/sda1
 104
 105
 106 .. _ceph-volume-simple-scan-json:
 107
 108 ``JSON`` contents
 109 -----------------
 110 The contents of the JSON object is very simple. The scan not only will persist
 111 information from the special OSD files and their contents, but will also
 112 validate paths and device UUIDs. Unlike what ``ceph-disk`` would do, by storing
 113 them in ``{device type}_uuid`` files, the tool will persist them as part of the
 114 device type key.
 115
 116 For example, a ``block.db`` device would look something like::
 117
 118     "block.db": {
 119         "path": "/dev/disk/by-partuuid/6cc43680-4f6e-4feb-92ff-9c7ba204120e",
 120         "uuid": "6cc43680-4f6e-4feb-92ff-9c7ba204120e"
 121     },
 122
 123 But it will also persist the ``ceph-disk`` special file generated, like so::
 124
 125     "block.db_uuid": "6cc43680-4f6e-4feb-92ff-9c7ba204120e",
 126
 127 This duplication is in place because the tool is trying to ensure the
 128 following:
 129
 130 # Support OSDs that may not have ceph-disk special files
 131 # Check the most up-to-date information on the device, by querying against LVM
 132 and ``blkid``
 133 # Support both logical volumes and GPT devices
 134
 135 This is a sample ``JSON`` metadata, from an OSD that is using ``bluestore``::
 136
 137     {
 138         "active": "ok",
 139         "block": {
 140             "path": "/dev/disk/by-partuuid/40fd0a64-caa5-43a3-9717-1836ac661a12",
 141             "uuid": "40fd0a64-caa5-43a3-9717-1836ac661a12"
 142         },
 143         "block.db": {
 144             "path": "/dev/disk/by-partuuid/6cc43680-4f6e-4feb-92ff-9c7ba204120e",
 145             "uuid": "6cc43680-4f6e-4feb-92ff-9c7ba204120e"
 146         },
 147         "block.db_uuid": "6cc43680-4f6e-4feb-92ff-9c7ba204120e",
 148         "block_uuid": "40fd0a64-caa5-43a3-9717-1836ac661a12",
 149         "bluefs": "1",
 150         "ceph_fsid": "c92fc9eb-0610-4363-aafc-81ddf70aaf1b",
 151         "cluster_name": "ceph",
 152         "data": {
 153             "path": "/dev/sdr1",
 154             "uuid": "86ebd829-1405-43d3-8fd6-4cbc9b6ecf96"
 155         },
 156         "fsid": "86ebd829-1405-43d3-8fd6-4cbc9b6ecf96",
 157         "keyring": "AQBBJ/dZp57NIBAAtnuQS9WOS0hnLVe0rZnE6Q==",
 158         "kv_backend": "rocksdb",
 159         "magic": "ceph osd volume v026",
 160         "mkfs_done": "yes",
 161         "ready": "ready",
 162         "systemd": "",
 163         "type": "bluestore",
 164         "whoami": "3"
 165     }