GNU userv

Put the security boundary where it ought to be.

userv (pronounced you-serve) is a program which, according to the specification, is

a Unix system facility to allow one program to invoke another when only limited trust exists between them.

It is a tool for system administrators, who often find themselves with a program running as one user which needs to be able to do certain things as another user. For example, my machine's news system needs to scan my users' newsrcs to ensure that the right newsgroups are fetched. Before userv that part of the news system had to run as root, and clumsily use `su'.

It is also a component for application authors. For example, imagine a version of `cron' which didn't need to run as root, so that a security bug in cron would just mean that bad people could get cron jobs to run at the wrong times, rather than everyone on the system being able to break in completely. Imagine being able to do sophisticated mail filtering at delivery time without the mail transfer or delivery agents needing to be root.


If you are subscribed to userv-discuss please send bug reports there; otherwise mail them to


I have set up mailinglists userv-announce and userv-discuss. The announcements list is moderated and will contain only announcements of important bugs, new versions, &c. The bug reports address mentioned above is also a mailing list; feel free to subscribe to it.

There are archives and subscription web pages, or you can subscribe by sending mail containing the word `subscribe' to or


Available for download from are: You can also access the project CVS repositories: userv is also available from the GNU Project FTP servers and their mirrors.

Copyright and licensing

userv is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program and documentation is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with userv, or one should be available above; if not, see

Ian Jackson /; more free software by me.

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This web page is Copyright (C)1996-2017 Ian Jackson. See the Copyright/acknowledgements.

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