BOOTPTAB(5)
NAME
bootptab - Internet Bootstrap Protocol server database
DESCRIPTION
The bootptab file is the configuration database file for
bootpd, the Internet Bootstrap Protocol server. It's for-
mat is similar to that of termcap(5) in which two-charac-
ter case-sensitive tag symbols are used to represent host
parameters. These parameter declarations are separated by
colons (:), with a general format of:
hostname:tg=value. . . :tg=value. . . :tg=value. . .
.
where 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 hostname (one with a "." as
the first character) and are used to provide default val-
ues used by other entries via the tc=.dummy-entry mecha-
nism. 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
df Merit 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
ns IEN-116 name server address list
nt NTP (time) Server (RFC 1129)
ra Reply address override
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 Vendor magic cookie selector
yd YP (NIS) domain name
ys YP (NIS) server address
There is also a generic tag, Tn, where n is an RFC1084
vendor field tag number. Thus it is possible to immedi-
ately take advantage of future extensions to RFC1084 with-
out 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 RFC1084-style bootp reply.
The following tags take a whitespace-separated list of IP
addresses: cs, ds, gw, im, lg, lp, ns, nt, ra, rl, and ts.
The ip, sa, sw, sm, and ys 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, hexadeci-
mal 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(3). 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.)
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 Ether-
net, 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 speci-
fied as either "ethernet" or "ieee802", then bootpd will
try to determine the hardware address using ether_hton(3).
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 boot-
file field of the bootp reply packet.
If the client provides a file name it is left as is. Oth-
erwise, if the bf option is specified its value is copied
into the reply packet. If the hd option is specified as
well, its value is prepended to the boot file copied into
the reply packet. The existence of the boot file is
checked only if the bs=auto option is used (to determine
the boot file size). A reply may be sent whether or not
the boot file exists.
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 bootpd of this
special root directory used by tftpd. (One may alterna-
tively use the bootpd "-c chdir" option.) 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 bootfile 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:
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 per-
form 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 RFC1084-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 RFC1084 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, regard-
less 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 back-
slash (\). 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 pre-
cede the hardware address.
An example /etc/bootptab file follows:
# 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/bootptab
SEE ALSO
bootpd(8) tftpd(8)
DARPA Internet Request For Comments RFC951, RFC1048,
RFC1084, Assigned Numbers