UTMPDUMP(1) User Commands UTMPDUMP(1)
utmpdump - dump UTMP and WTMP files in raw format
utmpdump [options] [filename]
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
Output appended data as the file grows.
-o, --output file
Write command output to file instead of standard output.
Undump, write back edited login information into the utmp or
Display version information and exit.
Display help text and exit.
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.
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.
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.
last(1), w(1), who(1), utmp(5)
The utmpdump command is part of the util-linux package and is available
from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-
util-linux July 2014 UTMPDUMP(1)