Ubuntu Manpage: dumpseg - print segment information of NILFS2

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.