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BOOTPTAB(5)               FreeBSD File Formats Manual              BOOTPTAB(5)

     bootptab - Internet Bootstrap Protocol server database

     The bootptab file is the configuration database file for bootpd(8), 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 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 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 (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 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 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, 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(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 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

     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 provides a file name it is left as is.  Otherwise, 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(8) 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
     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

     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

     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 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

     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(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 (

                   :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

FreeBSD 11.0-PRERELEASE        October 31, 1991        FreeBSD 11.0-PRERELEASE


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