bootptab(5) bootptab(5)
NAME
bootptab - Internet Bootstrap Protocol server database
DESCRIPTION
The bootptab file is the configuration database file for in.bootp(8),
the Internet Bootstrap Protocol server. Its format is similar to that
of termcap in which two-character case-sensitive tag symbols are used
to represent host parameters. These parameter declarations are sepa-
rated by colons (:), with a general format of:
hostname:tg=value...:tg=value...:tg=value...
hostname is the actual name of a BOOTP client (or a dummy entry), and
tg is a two-character tag symbol. Dummy entries have an invalid host-
name (one with a "." as the first character) and are used to provide
default values that can be used for 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 (i.e. :tg:). Currently recognized tags are listed below:
bf Bootfile
bs Bootfile size in 512-octet blocks
cs Date
df Dump file
dn Domain name
ds Domain name server address list
ef Extension file
gw Gateway address list
ha Host hardware address
hd Bootfile home directory
hn Send client's hostname to client
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
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bootptab(5) bootptab(5)
ns IEN-116 name server address list
ra Address to which the response is to be sent
rl Resource location protocol server address list
rp Root path to mount as root
sa TFTP server address client should use
sm Host subnet mask
sw Swap server address
tc Table continuation (points to similar template host entry)
td TFTP root directory used by secure TFTP servers
to Time offset in seconds from UTC
ts Time server address list
vm Selection criteria vendor information
There is also a generic tag, Tn, where n is an RFC1084 vendor field
tag number. Thus, it is possible to immediately take advantage of
future extensions to RFC1084 without being forced to modify in.bootp
first. Generic data may be represented as either a stream of hexade-
cimal numbers or as a quoted string of ASCII characters. The length of
the generic data is automatically determined and inserted into the
proper fields of the RFC1084-style BOOTP reply.
The following tags take a blankspace-separated list of IP addresses:
cs, ds, gw, im, lg, lp, ns, 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 bootp to look up the
IP address for that host name using gethostbyname(3N). If the ip tag
is not specified, bootp 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.)
The ht tag specifies the hardware type code as either an unsigned
decimal, octal, or hexadecimal integer or one of the following sym-
bolic 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, respec-
tively. The ha tag takes a hardware address which may be specified as
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a host name or in numeric form. Note that the numeric form must be
specified in hexadecimal form; 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 bootp will try to determine the hardware address
using etherhton.
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 speci-
fies 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(1M) to permit the file transfer.
Also, all filenames are first tried as filename.hostname and then sim-
ply as filename, thus providing for individual per-host bootfiles.
Some newer versions of tftpd provide a security feature to change
their root directory using the chroot(2) system call. The td tag may
be used to inform in.bootp of this special root directory used by
tftpd (alternatively, the in.bootp -c chdir option can be used). The
hd tag is actually 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:
:td=/tftpboot:hd=/bootfiles:bf=bootimage:
If your bootfiles are located directly in /tftpboot, use:
:td=/tftpboot:hd=/:bf=bootimage:
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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,
in.bootp will tell the client to perform TFTP at the same machine
in.bootp 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 automatically 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 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 RFC1084-style
reply), or cmu (which always forces a CMU-style reply). The hn tag
only permits a boolean operation; it does not take the usual equals-
sign and value. Its presence indicates that the hostname should be
sent to RFC1084 clients. in.bootp 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 another attempt is made.
In no case is an arbitrarily-truncated hostname sent (if nothing rea-
sonable will fit, nothing is sent).
Often, many host entries share common values for certain tags (such as
name servers.). 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 for
similar terminals. Note that in.bootp 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. 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 eli-
gible to be set again through the tc mechanism.
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Blank lines and lines beginning with # are ignored in the configura-
tion file. Host entries are separated from one another by new lines; 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.
Here is a sample /etc/bootptab file:
# Sample bootptab file (domain=andrew.cmu.edu)
.default:\
:hd=/usr/boot:bf=null:\
:ds=netserver, lancaster:\
:ns=pcs2, pcs1:\
:ts=pcs2, pcs1:\
:sm=255.255.255.0:\
:gw=gw.cs.cmu.edu:\
: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=128.2.13.42:\
: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:
FILES
/etc/inet/bootptab
SEE ALSO
tftpd(1M), bootp(8).
DARPA Internet Request For Comments RFC951, RFC1048, RFC1084, Assigned
Numbers.
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