www.LinuxHowtos.org

UTMPDUMP

Section: User Commands (1)
Updated: July 2014
Index Return to Main Contents

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.
-V, --version: Display version information and exit.
-h, --help: Display help text 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

The only 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.

AUTHOR

Michael Krapp

AVAILABILITY

The utmpdump command is part of the util-linux package and is available from Linux Kernel Archive

Index

File formats