Section: oidentd User Manual (8)
oidentd - flexible, RFC 1413 compliant ident daemon with NAT support
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.
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
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
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).
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.
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.
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
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.
Print a summary of options and exit.
Do not fork to background. This option may be useful for debugging, or for
running oidentd from a service manager like systemd(1) with
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).
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
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
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
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
Listen on the specified port instead of port 113.
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.
Suppress normal logging, showing only critical messages.
When a lookup fails, send the specified ident response as if it had
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.
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.
Close connections if no ident query is received within the specified number
of seconds. By default, connections are closed after 30 seconds.
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.
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.
Print version and build information and exit.
System-wide configuration file; see oidentd.conf(5).
User configuration files; see oidentd.conf(5).
Masquerading configuration file; see oidentd_masq.conf(5).
Originally written by Ryan McCabe.
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