BOOTPD(8C)

NAME
bootpd - Internet Boot Protocol server

SYNOPSIS
/etc/bootpd [ -s -ttimeout -d ] [ configfile [ dumpfile ] ]

DESCRIPTION
Bootpd implements an Internet Boot Protocol server as defined in RFC951 and RFC1048. It is normally run by /etc/inetd by including the following line in the file /etc/inetd.conf:

    bootps    dgram    udp    wait    root    /etc/bootpd    bootpd

This causes bootpd to be started only when a boot request arrives. If bootpd does not receive another boot request within fifteen minutes of the last one it received, it will exit to conserve system resources. The -t switch may be used to specify a different timeout value in minutes (e.g. -t20). A timeout value of zero means forever.

It is also possible to run bootpd in a standalone configuration using the -s switch (for example, at boot time from /etc/rc.local). This is probably the desired mode of operation for large network installations with many hosts. In this case, the -t switch has no effect since bootpd will never exit.

Each instance of the -d switch increases the level of debugging output.

Upon startup, bootpd first reads its configuration file, /etc/bootptab, and then begins listening for BOOTREQUEST packets. The configuration file has a format similar to that of termcap(5) in which two-character case-sensitive tag symbols are used to represent host parameters. These parameter declarations are separated by colons (:). The general format is:

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

where hostname is the actual name of a bootp client and tg is a two-character tag symbol. 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 (i.e. :tg:). The currently recognized tags are:

    bf    Bootfile
    bs    Bootfile size in 512-octet blocks
    cs    Cookie server address list
    ds    Domain name server address list
    gw    Gateway address list
    ha    Host hardware address
    hd    Bootfile home directory
    hn    Send hostname
    ht    Host hardware type (see Assigned Numbers RFC)
    im    Impress server address list
    ip    Host IP address
    lg    Log server address list
    lp    LPR server address list
    ns    IEN-116 name server address list
    rl    Resource location protocol server address list
    sm    Host subnet mask
    tc    Table continuation (points to similar "template" host entry)
    to    Time offset in seconds from UTC
    ts    Time server address list
    vm    Vendor magic cookie selector

There is also a generic tag, Tn, where n is an RFC1048 vendor field tag number. Thus it is possible to immediately take advantage of future extensions to RFC1048 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 RFC1048-style bootp reply.

The following tags take a whitespace-separated list of IP addresses: cs, ds, gw, im, lg, lp, ns, rl, and ts. The ip 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').

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 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).

The hostname, home directory, and bootfile are ASCII strings which may be optionally surrounded by double quotes ("). The client's request and the values of the hd and bf symbols determine how the server fills in the bootfile field of the bootp reply packet.

If the client specifies an absolute pathname and that file exists on the server machine, that pathname is returned in the reply packet. If the file cannot be found, the request is discarded; no reply is sent. If the client specifies a relative pathname, a full pathname is formed by prepending the value of the hd tag and testing for existence of the file. If the hd tag is not supplied in the configuration file or if the resulting boot file cannot be found, then the request is discarded.

Clients which specify null boot files will always elicit a reply from the server. The exact reply will again depend upon the hd and bf tags. If the bf tag gives an absolute pathname and the file exists, that pathname is returned in the reply packet. Otherwise, if the hd and bf tags together specify an accessible file, that filename is returned in the reply. If a complete filename cannot be determined or the file does not exist, the reply will contain a zeroed-out bootfile field.

In all these cases, existence of the file means that, in addition to actually being present, the file must have its public read access bit set, since this is required by tftpd(8) to permit the file transfer. Also, all filenames are first tried as filename.hostname and then simply as filename, thus providing for individual per-host bootfiles.

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 (which always forces an RFC1048-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. It's presence indicates that the hostname should be sent to RFC1048 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 doesn't actually exist and never sends bootp requests. This feature is similar to the tc feature of termcap(5) 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(5). 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
    default1:\
        :hd=/usr/boot:bf=null:\
        :ds=128.2.35.50 128.2.13.21:\
        :ns=0x80020b4d 0x80020ffd:\
        :ts=0x80020b4d 0x80020ffd:\
        :sm=255.255.0.0:gw=0x8002fe24:\
        :hn:vm=auto:to=-18000:\
        :T37=0x12345927AD3BCF:T99="Special ASCII string":
    carnegie:ht=6:ha=7FF8100000AF:ip=128.2.11.1:tc=default1:
    baldwin:ht=1:ha=0800200159C3:ip=128.2.11.10:tc=default1:
    wylie:ht=1:ha=00DD00CADF00:ip=128.2.11.100:tc=default1:
    arnold:ht=1:ha=0800200102AD:ip=128.2.11.102:tc=default1:
    bairdford:ht=1:ha=08002B02A2F9:ip=128.2.11.103:tc=default1:
    bakerstown:ht=1:ha=08002B0287C8:ip=128.2.11.104:tc=default1:
    # Special domain name server for next host
    butlerjct:ht=1:ha=08002001560D:ip=128.2.11.108:ds=128.2.13.42:tc=default1:
    gastonville:ht=6:ha=7FFF81000A47:ip=128.2.11.115:tc=default1:
    hahntown:ht=6:ha=7FFF81000434:ip=128.2.11.117:tc=default1:
    hickman:ht=6:ha=7FFF810001BA:ip=128.2.11.118:tc=default1:
    lowber:ht=1:ha=00DD00CAF000:ip=128.2.11.121:tc=default1:
    mtoliver:ht=1:ha=00DD00FE1600:ip=128.2.11.122:tc=default1:

Bootpd looks in /etc/services to find the port numbers it should use. Two entries are extracted: bootps -- the bootp server listening port, and bootpc -- the destination port used to reply to clients. If the port numbers cannot be determined this way, they are assumed to be 67 for the server and 68 for the client.

Bootpd rereads its configuration file when it receives a hangup signal, SIGHUP, or when it receives a bootp request packet and detects that the file has been updated. Hosts may be added, deleted or modified when the configuration file is reread. If bootpd is compiled with the -DDEBUG option, receipt of a SIGUSR1 signal causes it to dump its memory-resident database to the file /etc/bootpd.dump or the command-line-specified dumpfile.

FILES
/etc/bootptab
/etc/bootpd.dump
/etc/services

BUGS
Individual host entries must not exceed 1024 characters.

HISTORY

22-Jan-86  Bill Croft at Standford University
    Created.

30-Jul-86  David Kovar at Carnegie Mellon University
    Modified to CMU specifications.

24-Jul-87  Drew D. Perkins at Carnegie Mellon University
    Modified to use syslog. Added debugging dumps. Other bug fixes.

17-Jul-88  Walter L. Wimer at Carnegie Mellon University
    Added vendor information to conform to RFC1048. Adopted termcap-like file format to allow variable data.

SEE ALSO
inetd(8);
DARPA Internet Request For Comments RFC951, RFC1048, RFC1084, Assigned Numbers