dumpseg(8)

1DUMPSEG(8)                  System Manager's Manual                 DUMPSEG(8)
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NAME

6       dumpseg - print segment information of NILFS2
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SYNOPSIS

9       dumpseg [-hV]
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11       dumpseg [device] segment-number ...
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DESCRIPTION

14       The  dumpseg  program  is an analysis tool for on-disk logs of a NILFS2
15       file system found in device.  It displays the  configuration  of  every
16       log  stored  in  the segments specified by one or more segment-numbers.
17       The term segment here means a contiguous lump of disk blocks giving  an
18       allocation unit of NILFS2 disk space.  When device is omitted, it tries
19       to find an active NILFS2 file system from /proc/mounts.
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21       dumpseg is a tool for debugging rather than administration.  To list  a
22       summary of segments, lssu(1) is available instead.
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OPTIONS

25       -h, --help
26              Display help message and exit.
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28       -V, --version
29              Display version and exit.
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FIELD DESCRIPTION

32       dumpseg  shows the configuration of each log with the following fields,
33       where each field is printed in the style of ``field-name = value''.
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35       creation time
36              Creation date and time of the log.
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38       nfinfo Number of file information summaries.
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40       finfo  File information summary. This information starts with the  fol‐
41              lowing fields:
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43              ino    Inode number of the file.
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45              cno    Number  of the checkpoint that the blocks included in the
46                     file belong to.  For normal writings, this  is  equal  to
47                     the  latest checkpoint number.  For the writings involved
48                     in garbage collection, this indicates a  past  checkpoint
49                     number.
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51              nblocks
52                     Number  of  blocks  of the file written in the log.  This
53                     number is a sum of the number of data blocks  and  B-tree
54                     node  blocks.   The  contents of these blocks are written
55                     serially in the payload part of the log.   Only  modified
56                     or newly created blocks are written to each log.
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58              ndatblk
59                     Number of data blocks of the file written in the log.
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61              Then,  for each update block in the file, the following informa‐
62              tion will follow these headings.
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64              vblocknr
65                     Virtual block number.  Not printed for data blocks of the
66                     Disk Address Translation file (DAT file).
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68              blkoff Block  offset number.  Not printed for B-tree node blocks
69                     except for the DAT file.
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71              level  Level of B-tree node block.  Printed  only  for  the  DAT
72                     file.
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74              blocknr
75                     Block address on the device.  This is not an actual field
76                     in the summary but is calculated from the disk address of
77                     each log.
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AUTHOR

80       Koji Sato
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AVAILABILITY

83       dumpseg  is  part  of  the  nilfs-utils  package  and is available from
84       https://nilfs.sourceforge.io.
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