A filesystem library based in librados
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README

README

==============================================
libradosfs - A filesystem library based in RADOS
==============================================

libradosfs is a complete client-side implementation of filesystem-like
functionality based on the RADOS object store (Ceph).
libradosfs was designed according to the requirements of the CERN Data Storage
Services group in terms of scalability and flexibility: it provides a scale-out
namespace and pseudo-hierarchical storage view with optimized directory and file
access (no strict POSIX semantics), parallel metadata queries, modification time
propagation, file striping and other features.

libradosfs should not be confused with CephFS. CephFS is a high-performance
POSIX-compliant filesystem implementation built on top of RADOS and supported by
Inktank/Redhat.

libradosfs is published under the terms of the LGPLv3 license:
  http://www.gnu.org/licenses/lgpl-3.0.html


Usage
======

Here is a quick example of how to use libradosfs (it might also be a good idea to
take a look at the unit tests for further examples):

  #include <libradosfs.hh>

  int ret;

  // Initialize libradosfs
  radosfs::Filesystem fs;
  ret = fs.init("someusername", "/path/to/conf/ceph.conf");

  if (ret != 0)
    return ret;

  // Add pools for prefixes
  fs.addDataPool("data-pool", "/");
  fs.addMetadataPool("mtd-pool", "/");

  // Create a directory
  radosfs::Dir dir(&fs, "/users");
  ret = dir.create();

  if (ret != 0)
    return ret;

  // Create a directory for a user with UID and GID = 1000
  radosfs::Dir userdir(&fs, "/users/joe");
  ret = userdir.create(S_IRWXU, , false, 1000, 1000);

  if (ret != 0)
    return ret;

  // Change the current UID and GID to the user mentioned above
  // (further operations will be done under these ids)
  radosFs.setIds(1000, 1000);

  // Create a file as user 1000
  radosfs::File file(&radosFs, "/userdir/myfile");
  ret = file.create();

  if (ret != 0)
    return ret;


Tools
======

libradosfs comes with a libradosfs-fsck tool for checking the filesystem for
issues and possibly correct them.

Here is how to use it:

  $ libradosfs-fsck --conf=CLUSTER_CONF /:data-pool:mtd-pool --check-dirs=/users -R

  Check the directory "/users" recursively in the cluster configured by
  CLUSTER_CONF with the data pool "data-pool" and metadata pool "mtd-pool" set
  for objects with the prefix "/" (all files and directories)

  $ libradosfs-fsck --conf=CLUSTER_CONF /:data-pool:mtd-pool --check-paths=/users/joe/file1,/trash/

  Simply check the file "/users/joe/file1" and the directory "/trash/" (does not
  check its entries) using the cluster and pools configured as in the previous
  example.

  $ libradosfs-fsck --conf=PATH_TO_CLUSTER_CONF /:data-pool:mtd-pool --check-dirs=/ -R --fix

  Checks all files and directories recursively in the filesystem. When a fixable
  issue is found, it will be fixed. Currently, the only fixable issues are
  broken links (to inodes, in the logical path objects) and broken back links
  (in inodes, to their logical path objects).

  $ libradosfs-fsck --conf=PATH_TO_CLUSTER_CONF /:data-pool:mtd-pool --check-inodes --fix

  Checks all the inode objects in the configured pools ("data-pool" and
  "mtd-pool") and attempts to fix the issues found. As mentioned before, the
  only fixable issues are broken links in both directions.

  $ libradosfs-fsck --conf=PATH_TO_CLUSTER_CONF --check-inodes=data-pool-2

  Checks all the inode objects in the given pool ("data-pool"). In this case,
  since there are no pools configured, the check will be less thorough than
  in the previous example.

  Whenever the --fix option is used, the --dry option can also be included so it
  only reports what would have been fixed, without really doing it.

  Using the --verbose option (or -v) will show all the issues found and not only
  a summary. If used together with the fix option, it will show what was fixed
  and how. If the dry run option is also used, it will show what would be done
  for each fix attempt.