NAME

       dumpseg - print segment information of NILFS2

SYNOPSIS

       dumpseg [-hV]

       dumpseg [device] segment-number ...

DESCRIPTION

       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.

OPTIONS

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

       -V, --version
              Display version and exit.

FIELD DESCRIPTION

       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.

              nblocks
                     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.

              ndatblk
                     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.

              vblocknr
                     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 file.

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

AUTHOR

       Koji Sato

AVAILABILITY

       dumpseg    is    part    of    the    nilfs-utils    package   and   is   available   from
       https://nilfs.sourceforge.io.

SEE ALSO

       nilfs(8), lssu(1).