DUMPSEG(8)                  System Manager's Manual                 DUMPSEG(8)

       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 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).

nilfs-utils version 2.2            Apr 2014                         DUMPSEG(8)