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lssu - Man Page

list usage state of NILFS2 segments


lssu [options] [device]


lssu is a utility for displaying usage state of NILFS2 segments in device, where a segment is contiguous lump of disk blocks and an allocation unit of NILFS2 disk space.  When device is omitted, /proc/mounts is examined to find a NILFS2 file system.

This command will fail if the device has no active mounts of a NILFS2 file system.


-a,  --all

Do not hide clean segments.

-h,  --help

Display help message and exit.

-i index, --index=index

Skip index segments at start of input.

-l,  --latest-usage

Print usage status of the moment.

-n lines, --lines=lines

List only lines input segments.

-p period, --protection-period=period

Specify protection period.  This option is used when printing usage status of the moment (with -l option) to test if each block in segments is protected and is not reclaimable.  Optionally, the period parameter may be suffixed by one of the following units designators: ´s´, ´m´, ´h´, ´d´,´w´,´M´, or ´Y´, for seconds, minutes, hours, days, weeks, months, or years, respectively.

-V,  --version

Display version and exit.

Field Description

Every line of the lssu output consists of the following fields:


Segment number.


Creation date.


Creation time.


State of the segment.  It consists of the following flags:


The segment is active, meaning that it is recently created and cannot be reclaimed by the garbage collector.


The segment is dirty, meaning that it is in use.


The segment is erroneous, meaning that it has once caused an I/O error.  NILFS2 avoids allocating the segments with this flag.

p (optional)

The segment is protected, meaning that garbage collection for the segment is prevented for some reason, for instance, the protection period is not elapsed from its last modified time, the segment is pinned by the file system, or it is erroneous and unreclaimable, etc. This flag is displayed when -l option is specified.


Number of in-use blocks of the segment.

NLIVEBLOCKS (optional)

Number and ratio of in-use blocks of the moment.  This field is displayed when -l option is specified.


Koji Sato


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

See Also

nilfs(8), dumpseg(8).

Referenced By

dumpseg(8), nilfs(8).

Apr 2014 nilfs-utils version 2.2