---
name: "utmpdump"
section: "1"
platform: "linux"
package: "util-linux"
version: "2.42.4-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/utmpdump"
---

# utmpdump(1)

dump UTMP and WTMP files in raw format

## 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)](/utmp/5.md) is standardised. Textual dumps may become incompatible in future.

The version 2.28 was the last one that printed text output using [**ctime**(3)](/ctime/3.md) 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.

## AUTHORS

Michael Krapp

## SEE ALSO

[**last**(1)](/last/1.md), [**w**(1)](/w/1.md), [**who**(1)](/who/1.md), [**utmp**(5)](/utmp/5.md)

## REPORTING BUGS

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

## 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/\>.