bootptab -- Internet Bootstrap Protocol server database


hostname:tg=value ... :tg=value ... :tg=value ...


This manual page documents the required syntax and semantics for the configuration database file for bootpd(ADMN), the Internet Bootstrap Protocol server. By default, bootpd expects this file to be located at /etc/bootptab. The format of this file is as shown above where hostname is the actual name of a BOOTP client (or a ``dummy entry'') and tg is a two-character, case-sensitive tag symbol used to represent a host parameter. These parameter declarations are separated by colons (:). Dummy entries have an invalid hostname (one with a ``.'' as the first character) and are used to provide default values used by other entries via the ``tc=.dummy-entry'' mechanism. Most tags must be followed by an equals-sign and a value as above. Some may also appear in a boolean form with no value (that is, :tg:).

The currently recognized tags are:


Bootfile size in 512-octet blocks

Cookie server address list

Merit dump file

Domain name

Domain name server address list

Extension file

Gateway address list

Host hardware address

Bootfile home directory

Send client's hostname to client

Host hardware type (see RFC 1340 ``Assigned Numbers'')

Impress server address list

Host IP address

Log server address list

LPR server address list

IEN-116 name server address list

Reply address override

Resource location protocol server address list

Root path to mount as root

TFTP server address client should use

Host subnet mask

Swap server address

Table continuation (points to similar ``template'' host entry)

TFTP root directory used by ``secure'' TFTP servers

Time offset in seconds from UTC

Time server address list

Vendor magic cookie selector
There is also a generic tag, Tn, where n is an RFC 1084 vendor field tag number. Thus it is possible to immediately take advantage of future extensions to RFC 1084 without being forced to modify bootpd first. Generic data may be represented as either a stream of hexadecimal numbers or as a quoted string of ASCII characters. The length of the generic data is automatically determined and inserted into the proper field(s) of the RFC 1084-style bootp reply.

The following tags take a whitespace-separated list of IP addresses: cs, ds, gw, im, lg, lp, ns, ra, rl, and ts. The ip, sa, sw, and sm tags each take a single IP address. All IP addresses are specified in standard Internet ``dot'' notation and may use decimal, octal, or hexadecimal numbers (octal numbers begin with 0, hexadecimal numbers begin with '0x' or '0X'). Any IP addresses may alternatively be specified as a hostname, causing bootpd to lookup the IP address for that host name using gethostbyname(SLIB). If the ip tag is not specified, bootpd will determine the IP address using the entry name as the host name. (Dummy entries use an invalid host name to avoid automatic IP lookup.)

If the amount of vendor-extension information in a bootptab file entry is greater than 64 bytes, you must:

specify the ef tag with a filename value, such as ``ef=/bootfile/clientname''

run the bootpef command to compile the vendor-extension information into the specified file; see bootpef(ADMN).

NOTE: If an ef tag is specified in an entry and you fail to run bootpef, some vendor-extension information may never be sent to the client.

See RFC 1533 to identify which tags specify vendor-extension data. If an entry has more than 64 bytes and the ef tag is not specified, the bootpd server will send only 64 bytes in the reply packet and log which information did not fit. When an ef tag is present, the bootpd server sends a limited amount of vendor-extension data and the specified pathname in the vendor-extension field of the BOOTREPLY packet; bootpd assumes the client will retrieve the remainder of the vendor-extension information from the extension file. The specified pathname can be either a relative pathname or an absolute pathname. The location of a relative pathname is determined by the current directory of bootpef. The td and hd tag values have no effect on pathnames specified with the ef tag.

The ht tag specifies the hardware type code as either an unsigned decimal, octal, or hexadecimal integer or one of the following symbolic names: ethernet or ether for 10Mb Ethernet; ethernet3 or ether3 for 3Mb experimental Ethernet; ieee802, tr, or token-ring for IEEE 802 networks; pronet for Proteon ProNET Token Ring; or chaos, arcnet, or ax.25 for Chaos, ARCNET, and AX.25 Amateur Radio networks, respectively. The ha tag takes a hardware address which may be specified as a host name or in numeric form. Note that the numeric form must be specified in hexadecimal; optional periods and/or a leading '0x' may be included for readability. The ha tag must be preceded by the ht tag (either explicitly or implicitly; see tc below). If the hardware address is not specified and the type is specified as either ``ethernet'' or ``ieee802'', then bootpd will try to determine the hardware address using ether_hostton (see ether(SLIB)).

The hostname, home directory, and bootfile values are ASCII strings which may be optionally surrounded by double quotes (").

The client's request and the values of the td, hd, and bf tags determine how the server fills in the boot file field of the BOOTREPLY packet. If the client specifies any boot file pathname at all, the bootpd server sends that exact pathname back to the client in the BOOTREPLY packet; it does no processing. If the client specifies a null boot file, the server builds a boot file pathname from the td, hd, and bf tags. The server simply combines the values of these tags in the order listed above and returns the result in the BOOTREPLY packet. All three tags need not be present.

NOTE: The td and hd tags must start with ``/'' or bootpd will send no reply for that entry.

The tftpd(ADMN) server provides a security feature to change its root directory using the chroot(S) system call. The td tag may be used to inform bootpd of this special root directory used by tftpd. If the td tag is present, the hd tag is read relative to the root directory specified by the td tag. For example, if the real absolute path to your BOOTP client boot file is /tftpboot/bootfiles/bootimage, and tftpd uses /tftpboot as its ``secure'' directory, then specify the following in bootptab:


If your bootfiles are located directly in /tftpboot, use:


The sa tag may be used to specify the IP address of the particular TFTP server you wish the client to use. In the absence of this tag, bootpd will tell the client to perform TFTP to the same machine bootpd is running on.

The time offset to may be either a signed decimal integer specifying the client's time zone offset in seconds from UTC, or the keyword ``auto'' which uses the server's time zone offset. Specifying the to symbol as a boolean has the same effect as specifying ``auto'' as its value.

The bootfile size bs may be either a decimal, octal, or hexadecimal integer specifying the size of the bootfile in 512-octet blocks, or the keyword ``auto'' which causes the server to automatically calculate the bootfile size at each request. As with the time offset, specifying the bs symbol as a boolean has the same effect as specifying ``auto'' as its value.

The vendor magic cookie selector (the vm tag) may take one of the following keywords: ``auto'' (indicating that vendor information is determined by the client's request), ``rfc1048'' or ``rfc1084'' (which always forces an RFC 1084-style reply), or ``cmu'' (which always forces a CMU-style reply).

The hn tag is strictly a boolean tag; it does not take the usual equals-sign and value. Its presence indicates that the hostname should be sent to RFC 1084 clients. bootpd attempts to send the entire hostname as it is specified in the configuration file; if this will not fit into the reply packet, the name is shortened to just the host field (up to the first period, if present) and then tried. In no case is an arbitrarily-truncated hostname sent (if nothing reasonable will fit, nothing is sent).

Often, many host entries share common values for certain tags (such as name servers, etc.). Rather than repeatedly specifying these tags, a full specification can be listed for one host entry and shared by others via the tc (table continuation) mechanism. Often, the template entry is a dummy host which does not actually exist and never sends bootp requests. This feature is similar to the tc feature of termcap(F) for similar terminals. Note that bootpd allows the tc tag symbol to appear anywhere in the host entry, unlike termcap which requires it to be the last tag. Information explicitly specified for a host always overrides information implied by a tc tag symbol, regardless of its location within the entry. The value of the tc tag may be the hostname or IP address of any host entry previously listed in the configuration file.

Sometimes it is necessary to delete a specific tag after it has been inferred via tc. This can be done using the construction tag @ which removes the effect of tag as in termcap(F). For example, to completely undo an IEN-116 name server specification, use ``:ns@:'' at an appropriate place in the configuration entry. After removal with ``@'', a tag is eligible to be set again through the tc mechanism.

Blank lines and lines beginning with ``#'' are ignored in the configuration file. Host entries are separated from one another by newlines; a single host entry may be extended over multiple lines if the lines end with a backslash (\). It is also acceptable for lines to be longer than 80 characters. Tags may appear in any order, with the following exceptions: the hostname must be the very first field in an entry and the hardware type must precede the hardware address.

An example /etc/bootptab file follows:

# Sample bootptab file (

.default:\ :hd=/usr/boot:bf=null:\ :ds=netserver, lancaster:\ :ns=pcs2, pcs1:\ :ts=pcs2, pcs1:\ :sm=\\ :hn:to=-18000:

carnegie:ht=6:ha=7FF8100000AF:tc=.default: baldwin:ht=1:ha=0800200159C3:tc=.default: wylie:ht=1:ha=00DD00CADF00:tc=.default: arnold:ht=1:ha=0800200102AD:tc=.default: bairdford:ht=1:ha=08002B02A2F9:tc=.default: bakerstown:ht=1:ha=08002B0287C8:tc=.default:

# Special domain name server and option tags for next host butlerjct:ha=08002001560D:ds=\ :T37=0x12345927AD3BCF:\ :T99="Special ASCII string":\ :tc=.default:

gastonville:ht=6:ha=7FFF81000A47:tc=.default: hahntown:ht=6:ha=7FFF81000434:tc=.default: hickman:ht=6:ha=7FFF810001BA:tc=.default: lowber:ht=1:ha=00DD00CAF000:tc=.default: mtoliver:ht=1:ha=00DD00FE1600:tc=.default:



See also

bootpd(ADMN), bootpef(ADMN), ether(SLIB), tftpd(ADMN)

RFC 951, RFC 1048, RFC 1084, RFC 1340, RFC 1497, RFC 1533

© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003