Section: oidentd User Manual (8)
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oidentd - flexible, RFC 1413 compliant ident daemon with NAT support  


oidentd [OPTIONS]  


oidentd implements the Identification Protocol as described in RFC 1413. By default, oidentd replies with the username of the owner of connections. This behavior can be altered in oidentd.conf(5) and by using the options specified in this document.  


-a, --address=ADDRESS

Bind to the specified address. This option causes oidentd to listen for incoming connections only on the specified address or addresses instead of on all interfaces. This option may be specified more than once to configure multiple addresses.

-c, --charset=CHARSET

Inform clients that ident replies use the specified character set as defined in RFC 1340 or its successors. The default is not to send a character set to clients.

-C, --config=FILE

Use the specified system-wide configuration file. If this option is not given, oidentd defaults to /etc/oidentd.conf. The format of the system-wide configuration file is described in oidentd.conf(5).

-d, --debug

Show debug messages, including detailed lookup information that may be useful for diagnosing issues with failed lookups. This option is only available if oidentd was compiled with debugging support.

-e, --error

Hide error messages, returning UNKNOWN-ERROR for all errors. This includes the NO-USER, HIDDEN-USER and INVALID-PORT errors. This option may be used to conceal the fact that oidentd is hiding ident responses for a user.

-f, --forward=[PORT]

Forward requests for hosts masquerading through the server oidentd is running on to the host that established the corresponding connection. The target host must be running oidentd with the --proxy option, or some ident server returning static responses regardless of the query. If no port is specified, the default ident port (113) is used. If forwarding fails, oidentd falls back to the response specified in oidentd_masq.conf(5). This option implies --masquerade. The --masquerade-first option can be used to forward queries only if no response was specified in oidentd_masq.conf(5).

-g, --group=GROUP|GID

Run as the specified group or GID. If this option is not given, oidentd falls back to running as "oidentd", "nobody", "nogroup" or GID 65534, in this order. On systems that require oidentd to run as the superuser, a warning is shown and the group is not changed automatically.

-h, --help

Print a summary of options and exit.

-i, --foreground

Do not fork to background. This option may be useful for debugging, or for running oidentd from a service manager like systemd(1) with Type=simple.

-I, --stdio

Read a single ident query from standard input, write the response to standard output, then exit. This option may be useful for debugging, or when running oidentd from a listener daemon such as xinetd(8).

-l, --limit=MAX

Limit the maximum number of concurrent connections to the specified value. Further connections beyond this limit will be closed immediately without spawning a new process. If this option is not specified, no limit is enforced.

-m, --masquerade

Enable support for NAT connections, allowing Ident lookups intended for hosts masquerading through the server running oidentd. Ident responses for NAT connections can be configured in the oidentd_masq.conf(5) configuration file.

-M, --masquerade-first

If an entry matching the target host exists in the oidentd_masq.conf(5) configuration file, return the configured Ident response instead of forwarding the query. With this option, queries are forwarded only if no static response has been configured. If this option is not specified, the default behavior of --forward is to forward queries before checking the oidentd_masq.conf(5) file. This option implies --forward and --masquerade.

-o, --other=[OS]

Set an alternative operating system string to send alongside ident responses. Note that some clients may interpret queries as having failed when an unknown operating system is returned. If this option is not specified, the value UNIX is used. If this option is specified without an argument, OTHER is returned.

-p, --port=PORT

Listen on the specified port instead of port 113.

-P, --proxy=ORIGIN

Allow the specified host to forward queries to this instance using the --forward option. If --reply is not specified, this option must be enabled for oidentd to correctly handle forwarded connections.

-q, --quiet

Suppress normal logging, showing only critical messages.

-r, --reply=REPLY

When a lookup fails, send the specified ident response as if it had succeeded.

-R, --reply-all=REPLY

Send the specified reply in response to all well-formed queries. When this option is used, the configuration files are not read and connection lookups are never performed. Privileged initialization is not performed on systems that would otherwise require it, so unprivileged users can run oidentd with this option as long as they have permission to bind the requested port.

-S, --nosyslog

Log messages to the standard error stream, even if it is not a terminal. If standard error is a terminal, messages are written to it by default.

-t, --timeout=SECONDS

Close connections if no ident query is received within the specified number of seconds. By default, connections are closed after 30 seconds.

-u, --user=USER|UID

Run as the specified user or UID. If this option is not given, oidentd falls back to running as "oidentd", "nobody" or UID 65534, in this order. On systems that require oidentd to run as the superuser, a warning is shown and the user is not changed automatically.

-U, --udb

Look up connection owners using libudb. Lookup results that do not match any local user are returned verbatim. If a UDB lookup fails, the operating system is queried directly. This option also applies to NAT connections if the --masquerade option is specified.

-v, --version

Print version and build information and exit.



System-wide configuration file; see oidentd.conf(5).

~/.config/oidentd.conf, ~/.oidentd.conf

User configuration files; see oidentd.conf(5).


Masquerading configuration file; see oidentd_masq.conf(5).



Originally written by Ryan McCabe.  


Please report any bugs to  


oidentd.conf(5) oidentd_masq.conf(5)