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This is the FreeRADIUS implementation of the well known radius server program. Even though this program is largely compatible with Livingston’s radius version 2.0, it is not based on any part of that code.

FreeRADIUS is a high-performance and highly configurable RADIUS server. As a result, it can be difficult to configure in systems with complex requirements. Our suggestion is to proceed via the following steps:

  1. Always run the server in debugging mode ( radiusd -X ). We cannot emphasize this enough. If you are not running the server in debugging mode, you will not be able to see what is doing, and you will not be able to correct any problems.
  2. When editing the radiusd.conf file, change as little as possible, especially in the authorize{} section. The ordering of the modules is critical for the server to be able to "automatically" figure out how to handle the request. Changing the order of the modules ensures that the server will not work.
  3. When testing, start off by configuring a user and password in the users file. So long as the server knows about a user, and has a clear-text password for that user, almost all of the authentication methods will "just work".
  4. Gradually add more complex configurations to the server, while testing them as you go. If you start off by configuring the server in a complex configuration, you will never be able to debug it.
  5. Ask questions on the mailing list. When asking questions, include the output from debugging mode ( radiusd -X ). This information will allow people to help you. Without it, your message will get ignored.


RADIUS is a protocol spoken between an access server, typically a device connected to several modems or ISDN lines, and a radius server. When a user connects to the access server, (s)he is asked for a loginname and a password. This information is then sent to the radius server. The server replies with "access denied", or "access OK". In the latter case login information is sent along, such as the IP address in the case of a PPP connection.

The access server also sends login and logout records to the radius server so accounting can be done. These records are kept for each terminal server seperately in a file called detail, and in the wtmp compatible logfile /var/log/radwtmp.

Command Line Options

radiusd [-a] [-d] [-l] [-i] [-p] [-AcfnsSvXxyz]

Write a file detail.auth in addition to the standard detail file in the same directory. This file will contain all the authentication-request records. This can be useful for debugging, but not for normal operation.
This command line option is accepted only for backwards compatibility. It no longer does anything. See the configuration for the detail module in radiusd.conf.
Write the stripped usernames (without prefix or suffix) in the detail file instead of the raw record as received from the terminal server.
This command line option is deprecated. See the log_stripped_names configuration item in the radiusd.conf file.
-a accounting directory
This defaults to /var/log/radacct. If that directory exists, radiusd will write an ascii accounting record into a detail file for every login/logout recorded. The location of the detail file is acct_dir/terminal_server/detail.
This command line option is deprecated. See the radacctdir configuration item in the radiusd.conf file.
-l logging directory
This defaults to /var/log. Radiusd writes a logfile here called radius.log. It contains informational and error messages, and optionally a record of every login attempt (for aiding an ISP’s helpdesk). The special arguments stdout and stderr cause the information to get written to the standard output, or standard error instead. The special argument syslog sends the information with syslog(3).
This command line option is deprecated. See the log_dir configuration item in the radiusd.conf file.
-g facility
Specifies the syslog facility to be used with -l syslog. Default is daemon. Another reasonable choice would be authpriv.
-d config directory
Defaults to /etc/raddb. Radiusd looks here for its configuration files such as the dictionary and the users files.
-i ip-address
Defines which IP addres to bind to for sending and receiving packets - useful for multi-homed hosts.
This command line option is deprecated. See the bind_address configuration item in the radiusd.conf file.
If the radius server binary was compiled with dbm support, this flag tells it to actually use the database files instead of the flat users file.
This command line option is deprecated, and does not do anything.
This is still an experimental feature. Cache the password, group and shadow files in a hash-table in memory. This makes the radius process use a bit more memory, but username lookups in the password file are much faster.
After every change in the real password file (user added, password changed) you need to send a SIGHUP to the radius server to let it re-read its configuration and the password/group/shadow files!
This command line option is deprecated. See the cache configuration item for the unix module in the radiusd.conf file.
Do not fork, stay running as a foreground process.
-p port
Normally radiusd listens on the ports specified in /etc/services (radius and radacct). With this option radiusd listens on the specified port for authentication requests and on the specified port +1 for accounting requests.
This command line option is deprecated. See the port configuration item in the radiusd.conf file.
Run in "single server" mode. The server normally runs with multiple threads and/or processes, which can lower its response time to requests. Some systems have issues with threading, however, so running in "single server" mode may help to address those issues. In single server mode, the server will also not "daemonize" (auto-background) itself.
Print server version information and exit.
Debug mode. In this mode the server will print details of every request on its stderr output. Most useful in combination with -s. You can specify this option 2 times (-x -x or -xx) to get a bit more debugging output.
Extended debug mode. Equivalent to -sfxx, but simpler to explain.
Write details about every authentication request in the radius.log file.
This command line option is deprecated. See the log_auth configuration item in the radiusd.conf file.
Include the password in the radius.log file even for successful logins. This is very insecure!
This command line option is deprecated. See the log_auth_badpass and the log_auth_goodpass configuration items in the radiusd.conf file.


Radiusd uses a number of configuration files. Each file has it’s own manpage describing the format of the file. These files are:

The main configuration file, which sets the administrator-controlled items.
This file is usually static. It defines all the possible RADIUS attributes used in the other configuration files. You don’t have to modify it. It includes other dictionary files in the same directory.
Contains the IP address and a secret key for every client that wants to connect to the server.
[Deprecated] Contains an entry for every NAS (Network Access Server) in the network. This is not the same as a client, especially if you have radius proxy server in your network. In that case, the proxy server is the client and it sends requests for different NASes.
It also contains an abbreviated name for each terminal server, used to create the directory name where the detail file is written, and used for the /var/log/radwtmp file. Finally it also defines what type of NAS (Cisco, Livingston, Portslave) the NAS is.
Defines certain hints to the radius server based on the users’s loginname or other attributes sent by the access server. It also provides for mapping user names (such as Pusername -> username). This provides the functionality that the Livingston 2.0 server has as "Prefix" and "Suffix" support in the users file, but is more general. Of course the Livingston way of doing things is also supported, and you can even use both at the same time (within certain limits).
Defines the huntgroups that you have, and makes it possible to restrict access to certain huntgroups to certain (groups of) users.
Here the users are defined. On a typical setup, this file mainly contains DEFAULT entries to process the different types of logins, based on hints from the hints file. Authentication is then based on the contents of the UNIX /etc/passwd file. However, it is also possible to define all users, and their passwords, in this file.

See Also