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I believe RedHat (Fedora?) uses pam_cracklib: <a href="http://www.deer-run.com/~hal/sysadmin/pam_cracklib.html" rel="ugc">http://www.deer-run.com/~hal/sysadmin/pam_cracklib.html</a>
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I believe RedHat (Fedora?) uses pam_cracklib: http://www.deer-run.com/~hal/sysadmin/pam_cracklib.html [http://www.deer-run.com/~hal/sysadmin/pam_cracklib.html]

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Depends a little on what you consider to be a &quot;unique&quot; password. &nbsp;Do you mean that no one else on the system should have the same password as anyone else?
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Depends a little on what you consider to be a "unique" password.  Do you mean that no one else on the system should have the same password as anyone else?

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You can not do that, and, realistically, it would make very little sense if you could.<br />
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If you enforced the rule, the error message would alert the user that the password already exists. From there, it's only one step to try all usernames in /etc/passwd which is world-readable.<br />
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The encrypted passwords in /etc/shadow use username/uid as part of crypt salt, so even if 2 different users do have the same password, their hashes would look different in that file.
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You can not do that, and, realistically, it would make very little sense if you could.

If you enforced the rule, the error message would alert the user that the password already exists. From there, it's only one step to try all usernames in /etc/passwd which is world-readable.

The encrypted passwords in /etc/shadow use username/uid as part of crypt salt, so even if 2 different users do have the same password, their hashes would look different in that file.

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I realise that unique passwords would be very silly, I suspect &quot;unique&quot; should read &quot;strong&quot;.
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I realise that unique passwords would be very silly, I suspect "unique" should read "strong".

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Could you try your luck in helping me find a way to require unique passwords on Red Hat? &nbsp;Everything I've found so far is advice on CHOOSING a unique password - nothing so far on requiring that your users choose one.
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Could you try your luck in helping me find a way to require unique passwords on Red Hat?  Everything I've found so far is advice on CHOOSING a unique password - nothing so far on requiring that your users choose one.

How to Require Unique Passwords

Linux is a UNIX-like open source operating system with hundreds of distinct distributions, including: Fedora, openSUSE, Ubuntu, Debian, Slackware, Gentoo, CentOS, and Arch Linux. Linux is generally associated with web and database servers, but has become popular in many niche industries and applications.

Linux

Security is the protection of information systems from theft or damage to the hardware, the software, and the information on them, as well as from disruption or misdirection of the services they provide. The main goal of security is protecting assets, and an asset is anything of value and worthy of protection.  Information Security is a discipline of protecting information assets from threats through safeguards to achieve the objectives of confidentiality, integrity, and availability or CIA for short. On the other hand, disclosure, alteration, and disruption (DAD) compromise the security objectives.

Security

A Linux distribution is an operating system made as a software collection based on the Linux kernel and, often, on a package management system and are available for a variety of systems. A typical Linux distribution comprises a Linux kernel, GNU tools and libraries, additional software, documentation, a window system (the most common being the X Window System), a window manager, and a desktop environment. Most Linux systems are open-source software made available both as compiled binaries and in source code form, allowing modifications to the original software. Over three hundred distributions are in active development, including commercially backed distributions (such as Fedora, openSUSE and Ubuntu) and community-driven distributions (such as Debian, Slackware, Gentoo and Arch Linux).