System Administration Guide: IP Services

Differences Between dhcptags and inittab Files

The inittab file contains more information than the dhcptags file. The inittab file also uses a different syntax.

A sample dhcptags entry is as follows:

33 StaticRt - IPList Static_Routes

33 is the numeric code that is passed in the DHCP packet. StaticRt is the option name. IPList indicates that the data type for StaticRt must be a list of IP addresses. Static_Routes is a more descriptive name.

The inittab file consists of one-line records that describe each option. The format is similar to the format that defines symbols in dhcptab. The following table describes the syntax of the inittab file.




Name of the option. The option name must be unique within its option category, and not overlap with other option names in the Standard, Site, and Vendor categories. For example, you cannot have two Site options with the same name, and you should not create a Site option with the same name as a Standard option.


Identifies the namespace in which the option belongs. Must be one of the following: Standard, Site, Vendor, Field, or Internal.


Identifies the option when sent over the network. In most cases, the code uniquely identifies the option, without a category. However, in the case of internal categories such as Field or Internal, a code might be used for other purposes. The code might not be globally unique. The code should be unique within the option's category, and not overlap with codes in the Standard and Site fields.


Describes the data that is associated with this option. Valid types are IP, ASCII, Octet, Boolean, Unumber8, Unumber16, Unumber32, Unumber64, Snumber8, Snumber16, Snumber32, and Snumber64. For numbers, an initial U or S indicates that the number is unsigned or signed. The digits at the end indicate how many bits are in the number. For example, Unumber8 is an unsigned 8-bit number. The type is not case sensitive.


Describes how many units of data make up a whole value for this option.


Describes how many whole values are allowed for this option. 0 indicates an infinite number.


Describes which programs can use this information. Consumers should be set to sdmi, where:









A sample inittab entry is as follows:

StaticRt - Standard, 33, IP, 2, 0, sdmi

This entry describes an option that is named StaticRt. The option is in the Standard category, and is option code 33. The expected data is a potentially infinite number of pairs of IP addresses because the type is IP, the granularity is 2, and the maximum is infinite (0). The consumers of this option are sdmi: snoop, in.dhcpd, dhcpmgr, and dhcpinfo.