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.