Section: Maintenance Commands (8)
Updated: Apr 2014
dumpseg - print segment information of NILFS2
[device] segment-number ...
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
it tries to find an active NILFS2 file system from /proc/mounts
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.
shows the configuration of each log with the following fields, where
each field is printed in the style of ``field-name =
- creation time
Creation date and time of the log.
Number of file information summaries.
File information summary. This information starts with the following fields:
Inode number of the file.
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.
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).
Block offset number. Not printed for B-tree node blocks except for
the DAT file.
Level of B-tree node block. Printed only for the DAT file.
Block address on the device. This is not an actual field in the
summary but is calculated from the disk address of each log.
is part of the nilfs-utils package and is available from