# utmpdump

## NAME



           utmpdump - dump UTMP and WTMP files in raw format
    


## SYNOPSIS



           **utmpdump**[options] _filename_
    


## DESCRIPTION



           **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



           **-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



           **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



           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.
    


## AVAILABILITY



           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
           was found in the repository was 2025-08-05.) If you discover any
           rendering problems in this HTML version of the page, or you
           believe there is a better or more up-to-date source for the page,
           or you have corrections or improvements to the information in this
           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)
    


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