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       dumpseg - print segment information of NILFS2


       dumpseg [device] segment-number ...

       dumpseg -h


       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     Display help message 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 file.

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

                     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).