utmpdump(1) — Linux manual page

UTMPDUMP(1)                   User Commands                   UTMPDUMP(1)

NAME         top

       utmpdump - dump UTMP and WTMP files in raw format

SYNOPSIS         top

       utmpdump [options] filename

DESCRIPTION         top

       utmpdump is a simple program to dump UTMP and WTMP files in raw
       format, so they can be examined. utmpdump reads from stdin unless
       a filename is passed.

OPTIONS         top

       -f, --follow
           Output appended data as the file grows.

       -o, --output file
           Write command output to file instead of standard output.

       -r, --reverse
           Undump, write back edited login information into the utmp or
           wtmp files.

       -h, --help
           Display help text and exit.

       -V, --version
           Display version and exit.

NOTES         top

       utmpdump can be useful in cases of corrupted utmp or wtmp entries.
       It can dump out utmp/wtmp to an ASCII file, which can then be
       edited to remove bogus entries, and reintegrated using:

          utmpdump -r < ascii_file > wtmp

       But be warned, utmpdump was written for debugging purposes only.

   File formats
       Only the binary version of the utmp(5) is standardised. Textual
       dumps may become incompatible in future.

       The version 2.28 was the last one that printed text output using
       ctime(3) timestamp format. Newer dumps use millisecond precision
       ISO-8601 timestamp format in UTC-0 timezone. Conversion from
       former timestamp format can be made to binary, although attempt to
       do so can lead the timestamps to drift amount of timezone offset.

BUGS         top

       You may not use the -r option, as the format for the utmp/wtmp
       files strongly depends on the input format. This tool was not
       written for normal use, but for debugging only.

AUTHORS         top

       Michael Krapp

SEE ALSO         top

       last(1), w(1), who(1), utmp(5)

REPORTING BUGS         top

       For bug reports, use the issue tracker
       <https://github.com/util-linux/util-linux/issues>.

AVAILABILITY         top

       The utmpdump command is part of the util-linux package which can
       be downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
       part of the util-linux (a random collection of Linux utilities)
       project. Information about the project can be found at 
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
       bug report for this manual page, send it to
       util-linux@vger.kernel.org. This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2025-08-11. (At that time, the date of the most recent commit that
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       COLOPHON (which is not part of the original manual page), send a
       mail to man-pages@man7.org

util-linux 2.42-start-521-ec46  2025-08-09                    UTMPDUMP(1)

Pages that refer to this page: getutmp(3),  utmp(5)

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