Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (NetBSD-2.0)
Apropos / Subsearch:
optional field

BOOTPTAB(5)                   File Formats Manual                  BOOTPTAB(5)

       bootptab - Internet Bootstrap Protocol server database

       The  bootptab  file  is the configuration database file for bootpd, the
       Internet Bootstrap Protocol server.  Its format is similar to  that  of
       termcap(5)  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:


       where  hostname  is  the  actual  name  of  a bootp client (or a "dummy
       entry"), and tg is a two-character tag symbol.  Replies are returned to
       clients  only  if  an  entry  with  the client's Ethernet or IP address
       exists in the booptab file.  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 equal sign and a value as above.  Some may
       also appear in a boolean form with no value  (i.e.   :tg:).   The  cur-
       rently 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 immediately take  advantage  of  future
       extensions  to  RFC1084  without  being  forced to modify bootpd first.
       Generic data may be represented as either a stream of hexadecimal  num-
       bers  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 speci-
       fied 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 speci-
       fied  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

       The ht tag specifies the hardware type code as either an unsigned deci-
       mal, 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  net-
       works, 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 explic-
       itly  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

       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  bf  option  is  specified,  its value is copied into the reply
       packet.  Otherwise, the name supplied in the client  request  is  used.
       If  the hd option is specified, its value is prepended to the boot file
       in the reply packet, otherwise the path supplied in the client  request
       is  used.   The  existence  of  the boot file is NOT verified by bootpd
       because the boot file may be on some other machine.

       The bs option specified the size of the boot file.  It can  be  written
       as bs=auto which causes bootpd to determine the boot file size automat-

       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  alternatively  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:


       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 run-
       ning 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

       The vendor magic cookie selector (the vm tag) may take one of the  fol-
       lowing 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  oth-
       ers  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 term-
       cap(5) for similar terminals.  Note that bootpd allows the tc tag  sym-
       bol 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 con-
       figuration 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 appropri-
       ate 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 configura-
       tion 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 (domain=andrew.cmu.edu)

                 :ds=netserver, lancaster:\
                 :ns=pcs2, pcs1:\
                 :ts=pcs2, pcs1:\


            # Special domain name server and option tags for next host
                 :T99="Special ASCII string":\



       bootpd(8), tftpd(8),
       DARPA  Internet Request For Comments RFC951, RFC1048, RFC1084, Assigned

4.3 Berkeley Distribution      October 31, 1991                    BOOTPTAB(5)