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man pages section 1: User Commands

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Updated: Thursday, June 13, 2019
 
 

dhcpinfo(1)

Name

dhcpinfo - display values of parameters received through DHCP

Synopsis

dhcpinfo [-c] [-i interface] [-n limit] [-v 4|6] code
dhcpinfo [-c] [-i interface] [-n limit] [-v 4|6] identifier

Description

The dhcpinfo utility prints the DHCP–supplied value(s) of the parameter requested on the command line. The parameter can be identified either by its numeric code in the DHCP specification, or by its mnemonic identifier, as listed in dhcp_inittab(5). This command is intended to be used in command substitutions in the shell scripts invoked by init(8) at system boot. It first contacts the DHCP client daemon at system boot or in event scripts as described in dhcpagent(8). It first contacts the DHCP client daemon dhcpagent(8) to verify that DHCP has successfully completed on the requested interface. If DHCP has successfully completed on the requested interface, dhcpinfo retrieves the values for the requested parameter. Parameter values echoed by dhcpinfo should not be used without checking its exit status. See exit(1).

See dhcp_inittab(5) for the list of mnemonic identifier codes for all DHCP parameters. See RFC 2132, DHCP Options and BOOTP Vendor Extensions for more details on DHCPv4 parameters, and RFC 3315, Dynamic Host Configuration Protocol for IPv6 (DHCPv6), for more details on DHCPv6 parameters.

Output Format

The output from dhcpinfo consists of one or more lines of ASCII text; the format of the output depends upon the requested parameter. The number of values returned per line and the total number of lines output for a given parameter are determined by the parameter's granularity and maximum values, respectively, as defined by dhcp_inittab(5).

The format of each individual value is determined by the data type of the option, as determined by dhcp_inittab(5). The possible data types and their formats are listed below:

Data Type
Format
Unsigned Number
One or more decimal digits
UNUMBER8, UNUMBER16, UNUMBER32, UNUMBER64
Signed Number
One or more decimal digits, optionally preceded by a minus sign
SNUMBER8, SNUMBER16, SNUMBER32, SNUMBER64
IP Address
Dotted-decimal notation
IP
IPv6 Address
Colon-separated notation
IPv6
Octet
The string 0x followed by a two-digit hexadecimal value
OCTET
String
Zero or more ASCII characters
ASCII
DUID
DHCP Unique Identifier text
DUID
Domain Name
Standard dot-separated domain name, RFC 1035 format
DOMAIN
Classless Route
Classless Static Route Identifier, RFC 3442 format
CLROUTE

Note that the CLROUTE format for Classless Static Route option (option code 121) is displayed as tuples of destination/prefixlength-gateway per line. This provides a human-readable representation of the data that is specified in RFC 3442 for this option.

Options

The following options are supported:

–c

Displays the output in a canonical format. This format is identical to the OCTET format with a granularity of 1.

–i interface

Specifies the interface to retrieve values for DHCP parameters from. If this option is not specified, the primary interface is used.

If a primary interface has not been selected for the system by ifconfig(8) or for this command by –i, the system automatically selects an interface to consider as primary for the current command invocation. The selection chooses the interface whose name sorts lexically first, and that has DHCP parameters attached. This selection does not affect system state. Use ifconfig(8) to set a primary interface.

The recommended practice in the dhcpagent(8) eventhook scripts is to specify the desired interface with –i, rather than relying on primary selection.

For DHCPv6, the interface name used should be the name of the physical interface, not one of the logical interfaces created by dhcpagent.

–n limit

Limits the list of values displayed to limit lines.

–v4 | 6

Specifies the DHCP version to query. Use –v4for DHCPv4 and –v6 for DHCPv6.

Operands

The following operands are supported:

code

Numeric code for the requested DHCP parameter, as defined by the DHCP specification. Vendor options are specified by adding 256 to the actual vendor code for DHCPv4, and 65536 for DHCPv6.

identifier

Mnemonic symbol for the requested DHCP parameter, as listed in dhcp_inittab(5).

Exit Status

The following exit values are returned:

0

Successful operation.

2

The operation was not successful. The DHCP client daemon might not be running, the interface might have failed to configure, or no satisfactory DHCP responses were received.

3

Bad arguments.

4

The operation timed out.

6

System error (should never occur).

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Availability
system/network
Interface Stability
Committed

See Also

dhcp_inittab(5), attributes(7), dhcpagent(8), ifconfig(8), init(8)

Alexander, S., and R. Droms, RFC 2132, DHCP Options and BOOTP Vendor Extensions, Silicon Graphics, Inc., Bucknell University, March 1997.

Droms, R. , RFC 3315, Dynamic Host Configuration Protocol for IPv6 (DHCPv6), Cisco Systems, July 2003.

Lemon, T., S. Cheshire, and B. Volz. RFC 3442, The Classless Static Route Option for Dynamic Host Configuration Protocol (DHCP) version4, Network Working Group, December 2002.

Mockapetris, P.V. , RFC 1035, Domain names - implementation and specification, ISI, November 1987.