dumpseg - print segment information of NILFS2
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 Display help message 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 date and time of the log.
nfinfo Number of file information summaries.
finfo File information summary. This information starts with the
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
Koji Sato <firstname.lastname@example.org>
dumpseg is part of the nilfs-utils package and is available from