utmpdump - dump UTMP and WTMP files in raw format
is a simple program to dump UTMP and WTMP files in raw format,
so they can be examined. utmpdump
reads from stdin unless a
- -f, --follow
- Output appended data as the file grows.
- -o, --output file
- Write command output to file instead of standard
- -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.
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 >
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
for normal use, but for debugging only.
The utmpdump command is part of the util-linux package and is available from