# Fixing passwd(1) broken due to PAM

I encountered the following issue on Ubuntu. It can theoretically affect other unixy systems that use [PAM (pluggable authentication modules)](!W "Pluggable authentication module").

Suppose you find your system in this unusual state:

1. `passwd` is broken: it reports success without even prompting you for a password;
2. You can log in as any user without entering a password on the console and through `su` and `sudo`. (I did not notice this at first, since I logged in remotely with an SSH key.)

Then your system probably has bad PAM configuration.

This is how your session may look:

```plaintext
user@system$ passwd
passwd: password updated successfully
user@system$
```

The most likely cause is that the Unix authentication module is disabled. In order to reenable it on Debian and Ubuntu, run the following command:

```shell
sudo dpkg-reconfigure pam-runtime
```

In the menu that appears enable "Unix authentication".

On other operating systems look up how to enable PAM modules.

## Source

- <https://forums.debian.net/viewtopic.php?p=300244>

## See also

- NetBSD's nice [introductory article on PAM](https://www.netbsd.org/docs/guide/en/chap-pam.html). It is not especially platform-specific.

## Page metadata

URL: <https://dbohdan.com/passwd-pam-fix.md>

Published 2023-01-29, updated 2023-01-29.

Tags:

- how-to
- Linux
- security
- sysadmin
- troubleshooting
- Unix