Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Contact Us
Online Help
Domain Status
Man Pages

Virtual Servers

Topology Map

Server Agreement
Year 2038

USA Flag



Man Pages

checkpassword-pam - PAM-based checkpassword compatible authentication

checkpassword-pam [-s PAM-SERVICE] [-e|--noenv] -- prog args...

checkpassword-pam --help

checkpassword-pam --version

Additional debugging options (see below):

[--debug] [--stdout]

Additional rarely used options (see below):


checkpassword-pam uses PAM to authenticate the remote user with checkpassword protocol.

checkpassword-style programs are usually run by network server programs that wish to authenticate remote user.

checkpassword-pam uses PAM service name specified by PAM_SERVICE environment variable, or by the -s or --service command-line option.

After successful authentication, if --noenv option is not specified, checkpassword-pam sets up supplementary groups of authenticated user, its gid, its uid, and its working directory (those values are taken from the system user database).

Normally, checkpassword-pam switches to user home directory. If --no-chdir-home or -H option is specified, this step is skipped. This option is useful when you have automounted home directories, but mail is delivered to a central location.

Finally, checkpassword-pam executes prog with args as its arguments.

-- is used as usual to separate the checkpassword-pam own options from prog options.

checkpassword-pam logs authentication failures (or all actions, if --debug option is used) to syslog (or to stdout, if --stdout option is used).

checkpassword-pam uses contents of PAM_SERVICE environment variable to specify the PAM service name. This could be overriden by -s option, see above.

Before invoking prog, checkpassword-pam sets environment variables USER, HOME, and SHELL to appropriate values. If --noenv option is specified, this step is skipped and the variables are left alone. This is needed when you have virtual users which are not listed in your /etc/passwd, and you need to only do authentication. Setting up process environment is handled by some other application like setuidgid.

You can turn on debugging using the --debug option. checkpassword-pam starts to log all of its actions and the results of those actions to syslog (or to stdout, based on the state of --stdout option, see above).

There is a way to manually trace how the checkpassword-pam authenticates: use the shell redirection and the --stdout option. In this case checkpassword-pam reads checkpassword protocol data from stdin, and logs actions to stdout. You can trace the authentication for the given user and password with the following command-line (usually as root):

# echo -e "username\0password\0timestamp\0" \ | checkpassword-pam -s SERVICE \ --debug --stdout -- /usr/bin/id 3<&0

It will trace the PAM authentication process for the user username with password password, and run the id program, which will report the user and groups checkpassword-pam switched to.

The idea of this method is courtesy of Mark Delany <>.

If you've found a bug in checkpasswd-pam, please report it to

"PAM Administrator's Guide" for your operating system.

There are alternate older checkpassword-pam packages available. They are derived from original DJB's checkpassword code, and usually are less administrator-friendly than this version. You can tell those packages apart by looking at their version number: it is less than 0.95.

This version of checkpassword-pam was written from scratch by Alexey Mahotkin <>

checkpassword interface was designed by Daniel J. Bernstein.

22 Sep 2004 GNU/Linux

Search for    or go to Top of page |  Section 8 |  Main Index

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with ManDoc.