diff options
Diffstat (limited to 'doc/cephfs/cephfs-journal-tool.rst')
| -rw-r--r-- | doc/cephfs/cephfs-journal-tool.rst | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/doc/cephfs/cephfs-journal-tool.rst b/doc/cephfs/cephfs-journal-tool.rst new file mode 100644 index 00000000..bd70e817 --- /dev/null +++ b/doc/cephfs/cephfs-journal-tool.rst @@ -0,0 +1,238 @@ + +cephfs-journal-tool +=================== + +Purpose +------- + +If a CephFS journal has become damaged, expert intervention may be required +to restore the filesystem to a working state. + +The ``cephfs-journal-tool`` utility provides functionality to aid experts in +examining, modifying, and extracting data from journals. + +.. warning:: + + This tool is **dangerous** because it directly modifies internal + data structures of the filesystem. Make backups, be careful, and + seek expert advice. If you are unsure, do not run this tool. + +Syntax +------ + +:: + + cephfs-journal-tool journal <inspect|import|export|reset> + cephfs-journal-tool header <get|set> + cephfs-journal-tool event <get|splice|apply> [filter] <list|json|summary|binary> + + +The tool operates in three modes: ``journal``, ``header`` and ``event``, +meaning the whole journal, the header, and the events within the journal +respectively. + +Journal mode +------------ + +This should be your starting point to assess the state of a journal. + +* ``inspect`` reports on the health of the journal. This will identify any + missing objects or corruption in the stored journal. Note that this does + not identify inconsistencies in the events themselves, just that events are + present and can be decoded. + +* ``import`` and ``export`` read and write binary dumps of the journal + in a sparse file format. Pass the filename as the last argument. The + export operation may not work reliably for journals which are damaged (missing + objects). + +* ``reset`` truncates a journal, discarding any information within it. + + +Example: journal inspect +~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + # cephfs-journal-tool journal inspect + Overall journal integrity: DAMAGED + Objects missing: + 0x1 + Corrupt regions: + 0x400000-ffffffffffffffff + +Example: Journal import/export +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + # cephfs-journal-tool journal export myjournal.bin + journal is 4194304~80643 + read 80643 bytes at offset 4194304 + wrote 80643 bytes at offset 4194304 to myjournal.bin + NOTE: this is a _sparse_ file; you can + $ tar cSzf myjournal.bin.tgz myjournal.bin + to efficiently compress it while preserving sparseness. + + # cephfs-journal-tool journal import myjournal.bin + undump myjournal.bin + start 4194304 len 80643 + writing header 200.00000000 + writing 4194304~80643 + done. + +.. note:: + + It is wise to use the ``journal export <backup file>`` command to make a journal backup + before any further manipulation. + +Header mode +----------- + +* ``get`` outputs the current content of the journal header + +* ``set`` modifies an attribute of the header. Allowed attributes are + ``trimmed_pos``, ``expire_pos`` and ``write_pos``. + +Example: header get/set +~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + # cephfs-journal-tool header get + { "magic": "ceph fs volume v011", + "write_pos": 4274947, + "expire_pos": 4194304, + "trimmed_pos": 4194303, + "layout": { "stripe_unit": 4194304, + "stripe_count": 4194304, + "object_size": 4194304, + "cas_hash": 4194304, + "object_stripe_unit": 4194304, + "pg_pool": 4194304}} + + # cephfs-journal-tool header set trimmed_pos 4194303 + Updating trimmed_pos 0x400000 -> 0x3fffff + Successfully updated header. + + +Event mode +---------- + +Event mode allows detailed examination and manipulation of the contents of the journal. Event +mode can operate on all events in the journal, or filters may be applied. + +The arguments following ``cephfs-journal-tool event`` consist of an action, optional filter +parameters, and an output mode: + +:: + + cephfs-journal-tool event <action> [filter] <output> + +Actions: + +* ``get`` read the events from the log +* ``splice`` erase events or regions in the journal +* ``apply`` extract filesystem metadata from events and attempt to apply it to the metadata store. + +Filtering: + +* ``--range <int begin>..[int end]`` only include events within the range begin (inclusive) to end (exclusive) +* ``--path <path substring>`` only include events referring to metadata containing the specified string +* ``--inode <int>`` only include events referring to metadata containing the specified inode +* ``--type <type string>`` only include events of this type +* ``--frag <ino>[.frag id]`` only include events referring to this directory fragment +* ``--dname <string>`` only include events referring to this named dentry within a directory + fragment (may only be used in conjunction with ``--frag`` +* ``--client <int>`` only include events from this client session ID + +Filters may be combined on an AND basis (i.e. only the intersection of events from each filter). + +Output modes: + +* ``binary``: write each event as a binary file, within a folder whose name is controlled by ``--path`` +* ``json``: write all events to a single file, as a JSON serialized list of objects +* ``summary``: write a human readable summary of the events read to standard out +* ``list``: write a human readable terse listing of the type of each event, and + which file paths the event affects. + + +Example: event mode +~~~~~~~~~~~~~~~~~~~ + +:: + + # cephfs-journal-tool event get json --path output.json + Wrote output to JSON file 'output.json' + + # cephfs-journal-tool event get summary + Events by type: + NOOP: 2 + OPEN: 2 + SESSION: 2 + SUBTREEMAP: 1 + UPDATE: 43 + + # cephfs-journal-tool event get list + 0x400000 SUBTREEMAP: () + 0x400308 SESSION: () + 0x4003de UPDATE: (setattr) + / + 0x40068b UPDATE: (mkdir) + diralpha + 0x400d1b UPDATE: (mkdir) + diralpha/filealpha1 + 0x401666 UPDATE: (unlink_local) + stray0/10000000001 + diralpha/filealpha1 + 0x40228d UPDATE: (unlink_local) + diralpha + stray0/10000000000 + 0x402bf9 UPDATE: (scatter_writebehind) + stray0 + 0x403150 UPDATE: (mkdir) + dirbravo + 0x4037e0 UPDATE: (openc) + dirbravo/.filebravo1.swp + 0x404032 UPDATE: (openc) + dirbravo/.filebravo1.swpx + + # cephfs-journal-tool event get --path filebravo1 list + 0x40785a UPDATE: (openc) + dirbravo/filebravo1 + 0x4103ee UPDATE: (cap update) + dirbravo/filebravo1 + + # cephfs-journal-tool event splice --range 0x40f754..0x410bf1 summary + Events by type: + OPEN: 1 + UPDATE: 2 + + # cephfs-journal-tool event apply --range 0x410bf1.. summary + Events by type: + NOOP: 1 + SESSION: 1 + UPDATE: 9 + + # cephfs-journal-tool event get --inode=1099511627776 list + 0x40068b UPDATE: (mkdir) + diralpha + 0x400d1b UPDATE: (mkdir) + diralpha/filealpha1 + 0x401666 UPDATE: (unlink_local) + stray0/10000000001 + diralpha/filealpha1 + 0x40228d UPDATE: (unlink_local) + diralpha + stray0/10000000000 + + # cephfs-journal-tool event get --frag=1099511627776 --dname=filealpha1 list + 0x400d1b UPDATE: (mkdir) + diralpha/filealpha1 + 0x401666 UPDATE: (unlink_local) + stray0/10000000001 + diralpha/filealpha1 + + # cephfs-journal-tool event get binary --path bin_events + Wrote output to binary files in directory 'bin_events' + |