Provided by: nilfs-tools_2.1.0-1_amd64 bug


       dumpseg - print segment information of NILFS2


       dumpseg [-hV]

       dumpseg [device] segment-number ...


       The  dumpseg program is an analysis tool for on-disk logs of a NILFS2 file system found in
       device.  It displays the configuration of every log stored in the  segments  specified  by
       one or more segment-numbers.  The term segment here means a contiguous lump of disk blocks
       giving an allocation unit of NILFS2 disk space.  When device is omitted, it tries to  find
       an active NILFS2 file system from /proc/mounts.

       dumpseg  is  a  tool  for  debugging  rather  than  administration.   To list a summary of
       segments, lssu(1) is available instead.


       -h, --help
              Display help message and exit.

       -V, --version
              Display version and exit.


       dumpseg shows the configuration of each log with the following fields, where each field is
       printed in the style of ``field-name = value''.

       creation time
              Creation date and time of the log.

       nfinfo Number of file information summaries.

       finfo  File information summary. This information starts with the following fields:

              ino    Inode number of the file.

              cno    Number  of  the  checkpoint  that the blocks included in the file belong to.
                     For normal writings, this is equal to the latest checkpoint number.  For the
                     writings  involved  in  garbage collection, this indicates a past checkpoint

                     Number of blocks of the file written in the log.  This number is  a  sum  of
                     the  number  of  data  blocks and B-tree node blocks.  The contents of these
                     blocks are written serially in the payload part of the log.   Only  modified
                     or newly created blocks are written to each log.

                     Number of data blocks of the file written in the log.

              Then,  for  each  update  block  in the file, the following information will follow
              these headings.

                     Virtual block number.  Not printed for  data  blocks  of  the  Disk  Address
                     Translation file (DAT file).

              blkoff Block  offset number.  Not printed for B-tree node blocks except for the DAT

              level  Level of B-tree node block.  Printed only for the DAT file.

                     Block address on the device.  This is not an actual field in the summary but
                     is calculated from the disk address of each log.


       Koji Sato <>


       dumpseg is part of the nilfs-utils package and is available from


       nilfs(8), lssu(1).