dumpseg - print segment information of NILFS2
dumpseg [-hV]
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.
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.
dumpseg is part of the nilfs-utils package and is available
from http://nilfs.sourceforge.net.