IDENTD(8)

IDENTD(8) | System Manager's Manual | IDENTD(8)

# NAME

`identd` —
TCP/IP Ident protocol server

# SYNOPSIS

`identd` | [`-46beIilNnr`] [`-a` address] [`-c` charset] [`-F` format] [`-f` username] [`-g` uid] [`-L` username] [`-m` filter] [`-o` osname] [`-P` address] [`-p` portno] [`-t` seconds] [`-u` uid]

# DESCRIPTION

`identd` is a TCP/IP server which implements the user identification protocol as specified in RFC 1413.

`identd` operates by looking up specific TCP/IP connections and returning information which may or may not be associated with the process owning the connection.

The following options are available:

`-4`
  Bind to IPv4 addresses only (valid with flag `-b`).
`-6`
  Bind to IPv6 addresses only (valid with flag `-b`).
`-a` address
  Bind to the specified address. This may be an IPv4 or IPv6 address or even a hostname. If a hostname is specified then `identd` will resolve it to an address (or addresses) and will bind this address (valid with flag `-b`).
`-b`
  Run in the background (as daemon).
`-c` charset
  Specify an optional character set designator to be included in replies. charset should be a valid charset set as described in the MIME RFC in upper case characters.
`-e`
  Return “UNKNOWN-ERROR” instead of the usual “NO-USER” or “INVALID-PORT” error replies.
`-F` format
  Specify the format to display info. The allowed format specifiers are:

      %u	print user name
      %U	print user number
      %g	print (primary) group name
      %G	print (primary) group number
      %l	print list of all groups by name
      %L	print list of all groups by number

  The lists of groups (%l, %L) are comma-separated, and start with the primary group which is not repeated. Any other characters (preceded by %, and those not preceded by it) are printed literally.

`-f` username
  Specify a fall back username. If the lookup fails then this username will be returned. This can be useful for when running this service on a NAT host and not using the forward/proxy functionality.
`-g` gid
  Specify the group id number or name which the server should switch to after binding itself to the TCP/IP port.
`-I`
  Same as `-i` but without the restriction that the username in .ident must not match an existing user.
`-i`
  If the .ident file exists in the home directory of the identified user, return the username found in that file instead of the real username. If the username found in .ident is that of an existing user, then the real username will be returned.
`-L` username
  Specify a “lie” username. `identd` will return this name for all valid ident requests.
`-l`
  Use syslogd(8) for logging purposes.
`-m` filter
  Enables forwarding of ident queries. The filter argument specifies which packet filter should be used to lookup the connections, currently ‘ipfilter’, ‘npf’, and ‘pf’ are supported packet filters. Note that `identd` changes the ident queries to use the local port on the NAT host instead of the local port on the forwarding host. This is needed because otherwise we can't do a lookup on the proxy host. On the proxy host, “proxy mode” should be enabled with the `-P` flag or “lying mode” with the `-L` flag.
`-N`
  Enable .noident files. If this file exists in the home directory of the identified user then return “HIDDEN-USER” instead of the normal USERID response.
`-n`
  Return numeric user IDs instead of usernames.
`-o` osname
  Return osname instead of the default “UNIX”.
`-P` address
  Specify a proxy server which will be used to receive proxied ident queries from. See also the `-m` flag how this operates.
`-p` portno
  Specify an alternative port number under which the server should run. The default is port 113 (valid with flag `-b`).
`-r`
  Return a random name of alphanumeric characters. If the `-n` flag is also enabled then a random number will be returned.
`-t` seconds
  Specify a timeout for the service. The default timeout is 30 seconds.
`-u` uid
  Specify the user id number or name to which the server should switch after binding itself to the TCP/IP port.

# FILES

/etc/inetd.conf

# EXAMPLES

`identd` operates from inetd(8) or as standalone daemon. Put the following lines into inetd.conf(5) to enable `identd` as an IPv4 and IPv6 service via inetd:

ident stream tcp nowait nobody /usr/libexec/identd identd -l

ident stream tcp6 nowait nobody /usr/libexec/identd identd -l

To run `identd` as standalone daemon, use the `-b` flag.

# SEE ALSO

inetd.conf(5), inetd(8)

# AUTHORS

This implementation of `identd` is written by Peter Postma ⟨peter@NetBSD.org⟩.

# CAVEATS

Since `identd` should typically not be run as a privileged user or group, .ident files for use when running with the `-I` or `-i` flags will need to be world accessible. The same applies for .noident files when running with the `-N` flag.

When forwarding is enabled with the `-m` flag then `identd` will need access to either /dev/ipnat (ipfilter), /dev/pf (pf), or /dev/npf. Since it's not a good idea to run `identd` under root, you'll need to adjust group owner/permissions to the device(s) and run `identd` under that group.

December 9, 2016 | NetBSD 9.4