DUMPSEG(8)

📦
version 2.3.1 · 2 versions
, in alpine 3.24, arch rolling, nixpkgs unstable

💾 DUMPSEG — the dumpseg(8) page, but make it cute ✨

okay bestie, gather round, because we're about to talk about dumpseg from the System Manager's Manual section 8, and honestly? it's giving forensic girlboss 🔍💅

🌸 NAME 🌸

dumpseg — print segment information of NILFS2 🦋

✨ SYNOPSIS ✨

dumpseg [-hV]

dumpseg [device|node] segment-number ...

💖 DESCRIPTION 💖

so, the dumpseg program is an analysis tool for on-disk logs of a NILFS2 file system found in device. It shows you the configuration of every single log stored in the segments you specify with one or more *segment-number*s. no cap, every log. 👑

and when we say segment here, we mean a contiguous lump of disk blocks that acts as the allocation unit of NILFS2 disk space. that's the vibe. 🧱

device can be a block device, or it can be a filesystem node (a file or a directory) sitting on the filesystem. either one works, she's flexible like that. 🫶

and if you just... don't give her a device at all? she tries to find an active NILFS2 file system from /proc/mounts. she'll go looking for her own snack. iconic. 🍓

heads up bestie: dumpseg is a tool for debugging rather than administration. she's backstage, not front-of-house. if you want a summary of segments, lssu(1) is available instead. different girl, different job. 💅

🎀 OPTIONS 🎀

  • -h, --help — Display help message and exit. (she tells you how she works, then dips ✌️)
  • -V, --version — Display version and exit. (just the number, then gone 🌈)

🔥 FIELD DESCRIPTION 🔥

dumpseg shows the configuration of each log with these fields, and each field gets printed in the style of `field-name = value`. cute little key-value moment, we love a consistent format. ⭐

  • 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. no unnecessary rewrites, she's efficient 💅
    • 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. (she's doing math behind the scenes, respect her 🧮)

👑 AUTHOR 👑

Koji Sato 🌟

🌈 AVAILABILITY 🌈

dumpseg is part of the nilfs-utils package and is available from https://nilfs.sourceforge.io. go get her 🛍️

💜 SEE ALSO 💜

nilfs(8), lssu(1).

and that's the whole page, bestie!! this was nilfs-utils version 2.3, dated Jan 2026 — sending you all the segment-analysis energy, mwah 💖🎀🦋

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