o2info(1) Show OCFS2 file system information.


o2info [-C|--cluster-coherent] [--fs-features] [--volinfo] [--mkfs] [--freeinode] [--freefrag chunksize] [--space-usage] [--filestat] <device or file>


o2info shows information about OCFS2 file systems. It differs from debugfs.ocfs2(8) in that it allows users with limited read priviledges to query similar information. Users do not have to have the read privilege on the device as is expected by debugfs.ocfs2(8). This utility allows users to provide a path to an object on a mounted file system. The user needs to have the read priviledge on that object.


-C, --cluster-coherent
Force cluster coherency when querying a mounted file systems. The is disabled by default. Enable this only if accurate information is required as it involves taking cluster locks.

Show all the file system features (compat, incompat, ro compat) enabled on the file system.

Show file system information such as label, uuid, block and cluster sizes, node slots, etc.

Show file system information in mkfs.ocfs2(8) format.

Show the inode (allocated/free) count for all slots in the file system.

--freefrag chunksize
Show the free space fragmentation of the file system. The chunksize should be equal to or greater than the cluster size.

Show the disk space used by a file in block sized units. It also provides the block count of the holes, shared extents and unwritten extents.

Show the extended stat(1) information that includes the number of clusters consumed by extended attributes, unwritten extents, shared extents and holes, along with the file fragmentation score.

-V, --version
Show version and exit.

-h, --help
Show help and exit.


The utility uses custom info ioctls to query information from a mounted file system. As these info ioctls were added starting in Linux kernel 2.6.37, this utility will not work on mounted OCFS2 file systems running on systems having older kernels.


Non-priviledged users can query the volume information by providing the path to a file on a mounted file system. Priviledged users can provide the path to the device.

# o2info --volinfo /ocfs2/testfile
       Label: webhome
        UUID: 8AB016CD59FC4327A2CDAB69F08518E3
  Block Size: 4096
Cluster Size: 131072
  Node Slots: 8
    Features: backup-super strict-journal-super sparse extended-slotmap 
    Features: inline-data xattr indexed-dirs refcount discontig-bg clusterinfo 
    Features: unwritten

The same goes for querying file system fragmentation.

# o2info --freefrag 128 /ocfs2/testfile
Blocksize: 4096 bytes
Clustersize: 131072 bytes
Total clusters: 409599
Free clusters: 376537 (91.92%)
Min. free extent: 256 KB 
Max. free extent: 4091648 KB
Avg. free extent: 172672 KB
Chunksize: 131072 bytes (1 clusters)
Total chunks: 409600
Free chunks: 376537 (91.9%)
Extent Size Range :  Free extents  Free Clusters  Percent
  256K...  512K-  :             4            10    0.00%
  512K... 1024K-  :           251          1179    0.31%
    1M...    2M-  :             5            72    0.02%
    8M...   16M-  :             3           288    0.08%
   32M...   64M-  :             1           447    0.12%
  128M...  256M-  :             2          3371    0.90%
    1G...    2G-  :             1         13823    3.67%
    2G...    4G-  :            12        357347   94.90%


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