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dhcpd.leases(5)		      File Formats Manual	       dhcpd.leases(5)

NAME
       dhcpd.leases - DHCP client lease	database

DESCRIPTION
       The Internet Systems Consortium DHCP Server keeps a persistent database
       of leases that it has assigned.	This database  is  a  free-form	 ASCII
       file  containing	a series of lease declarations.	 Every time a lease is
       acquired, renewed or released, its new value is recorded	at the end  of
       the  lease  file.   So if more than one declaration appears for a given
       lease, the last one in the file is the current one.

       When dhcpd is first installed, there is no lease	 database.    However,
       dhcpd  requires	that a lease database be present before	it will	start.
       To make the initial lease database, just	create an  empty  file	called
       DBDIR/dhcpd.leases.   You can do	this with:

	    touch DBDIR/dhcpd.leases

       In  order to prevent the	lease database from growing without bound, the
       file is rewritten from time to time.   First, a temporary  lease	 data-
       base  is	created	and all	known leases are dumped	to it.	 Then, the old
       lease database is renamed  DBDIR/dhcpd.leases~.	  Finally,  the	 newly
       written lease database is moved into place.

FORMAT
       Lease  descriptions  are	 stored	in a format that is parsed by the same
       recursive  descent  parser  used	 to   read   the   dhcpd.conf(5)   and
       dhclient.conf(5)	 files.	  Lease	 files can contain lease declarations,
       and  also  group	 and  subgroup	declarations,  host  declarations  and
       failover	state declarations.  Group, subgroup and host declarations are
       used to record objects created using the	OMAPI protocol.

       The lease file is a log-structured file - whenever a lease changes, the
       contents	of that	lease are written to the end of	the file.   This means
       that it is entirely possible and	quite reasonable for there to  be  two
       or  more	 declarations  of the same lease in the	lease file at the same
       time.   In that case, the instance of that particular  lease  that  ap-
       pears last in the file is the one that is in effect.

       Group,  subgroup	and host declarations in the lease file	are handled in
       the same	manner,	except that if any of these  objects  are  deleted,  a
       rubout  is  written to the lease	file.	This is	just the same declara-
       tion, with { deleted; } in the scope of	the  declaration.    When  the
       lease  file  is	rewritten, any such rubouts that can be	eliminated are
       eliminated.   It	is possible to delete a	declaration in the  dhcpd.conf
       file;  in  this	case,  the  rubout  can	 never	be eliminated from the
       dhcpd.leases file.

THE LEASE DECLARATION
       lease ip-address	{ statements...	}

       Each lease declaration includes the single IP  address  that  has  been
       leased to the client.   The statements within the braces	define the du-
       ration of the lease and to whom it is assigned.

       starts date;
       ends date;
       tstp date;
       tsfp date;
       atsfp date;
       cltt date;

       The start and end time of a lease are recorded  using  the  starts  and
       ends statements.	  The tstp statement is	specified if the failover pro-
       tocol is	being used, and	indicates what time the	peer has been told the
       lease  expires.	  The tsfp statement is	also specified if the failover
       protocol	is being used, and indicates the lease expiry  time  that  the
       peer  has  acknowledged.	  The  atsfp statement is the actual time sent
       from the	failover partner.  The cltt statement  is  the	client's  last
       transaction time.

       The date	is specified in	two ways, depending on the configuration value
       for the db-time-format parameter.  If it	was set	to default,  then  the
       date fields appear as follows:

       weekday year/month/day hour:minute:second

       The weekday is present to make it easy for a human to tell when a lease
       expires - it's specified	as a number from zero to six, with zero	 being
       Sunday.	 The  day  of week is ignored on input.	 The year is specified
       with the	century, so it should generally	be four	digits except for  re-
       ally  long  leases.  The	month is specified as a	number starting	with 1
       for January.  The day of	the month is likewise specified	starting  with
       1.   The	hour is	a number between 0 and 23, the minute a	number between
       0 and 59, and the second	also a number between 0	and 59.

       Lease times are specified in Universal Coordinated Time (UTC),  not  in
       the  local time zone.  There is probably	nowhere	in the world where the
       times recorded on a lease are always the	same as	wall clock times.   On
       most  unix  machines, you can display the current time in UTC by	typing
       date -u.

       If the db-time-format was configured to local, then the date fields ap-
       pear as follows:

	epoch  _seconds-since-epoch_;  #  _day-name_ _month-name_ _day-number_
       _hours_:_minutes_:_seconds_ _year_

       The seconds-since-epoch is as according to  the	system's  local	 clock
       (often  referred	 to  as	"unix time").  The # symbol supplies a comment
       that describes what actual time this is as according  to	 the  system's
       configured timezone, at the time	the value was written.	It is provided
       only for	human inspection.

       If a lease will never expire, date is never instead of an actual	date.

       hardware	hardware-type mac-address;

       The hardware statement records the MAC address of the network interface
       on which	the lease will be used.	  It is	specified as a series of hexa-
       decimal octets, separated by colons.

       uid client-identifier;

       The uid statement records the client identifier used by the  client  to
       acquire	the  lease.    Clients are not required	to send	client identi-
       fiers, and this statement only appears if the client did	in  fact  send
       one.    Client  identifiers  are	 normally an ARP type (1 for ethernet)
       followed	by the MAC address, just like in the hardware  statement,  but
       this is not required.

       The client identifier is	recorded as a colon-separated hexadecimal list
       or as a quoted string.	If it is recorded as a quoted  string  and  it
       contains	 one  or  more	non-printable characters, those	characters are
       represented as octal escapes - a	backslash character followed by	 three
       octal digits.

       client-hostname hostname	;

       Most DHCP clients will send their hostname in the host-name option.  If
       a client	sends its hostname in this way,	the hostname  is  recorded  on
       the  lease  with	a client-hostname statement.   This is not required by
       the protocol, however, so many specialized DHCP clients do not  send  a
       host-name option.

       abandoned;

       The  abandoned  statement  indicates that the DHCP server has abandoned
       the lease.   In that case, the abandoned	statement will be used to  in-
       dicate  that  the  lease	 should	 not  be  reassigned.	Please see the
       dhcpd.conf(5) manual page for information about abandoned leases.

       binding state state; next binding state state;

       The binding state statement declares the	lease's	binding	 state.	  When
       the  DHCP  server  is  not  configured  to use the failover protocol, a
       lease's binding state will be either active  or	free.	 The  failover
       protocol	 adds  some  additional	 transitional  states,	as well	as the
       backup state, which indicates that the lease is available  for  alloca-
       tion by the failover secondary.

       The  next  binding  state statement indicates what state	the lease will
       move to when the	current	state expires.	 The  time  when  the  current
       state expires is	specified in the ends statement.

       option agent.circuit-id string; option agent.remote-id string;

       The  option  agent.circuit-id and option	agent.remote-id	statements are
       used to record the circuit ID and remote	ID options send	by  the	 relay
       agent,  if  the	relay  agent  uses the relay agent information option.
       This allows these options to be used consistently in conditional	evalu-
       ations  even  when  the client is contacting the	server directly	rather
       than through its	relay agent.

       set variable = value;

       The set statement sets the value	of a variable on the lease.  For  gen-
       eral information	on variables, see the dhcp-eval(5) manual page.

       The ddns-text variable

       The  ddns-text variable is used to record the value of the client's TXT
       identification record when the interim ddns update style	has been  used
       to update the DNS for a particular lease.

       The ddns-fwd-name variable

       The ddns-fwd-name variable records the value of the name	used in	updat-
       ing the client's	A record if a DDNS update has been  successfully  done
       by  the server.	 The server may	also have used this name to update the
       client's	PTR record.

       The ddns-client-fqdn variable

       If the server is	configured to use the interim ddns update  style,  and
       is  also	configured to allow clients to update their own	fqdns, and the
       client did in fact update its own fqdn, then the	ddns-client-fqdn vari-
       able records the	name that the client has indicated it is using.	  This
       is the name that	the server will	have used to update the	 client's  PTR
       record in this case.

       The ddns-rev-name variable

       If  the server successfully updates the client's	PTR record, this vari-
       able will record	the name that the DHCP server used for the PTR record.
       The  name  to  which the	PTR record points will be either the ddns-fwd-
       name or the ddns-client-fqdn.

       The vendor-class-identifier variable

       The server retains the client-supplied Vendor Class  Identifier	option
       for  informational  purposes,  and to render them in DHCPLEASEQUERY re-
       sponses.

       on events { statements... } The on statement records a list  of	state-
       ments  to execute if a certain event occurs.   The possible events that
       can occur for an	active lease are release and expiry.   More  than  one
       event can be specified -	if so, the events are separated	by '|' charac-
       ters.

       bootp; reserved;	 These	two  statements	 are  effectively  flags.   If
       present,	 they indicate that the	BOOTP and RESERVED failover flags, re-
       spectively, should be set.   BOOTP  and	RESERVED  dynamic  leases  are
       treated	differently  than  normal  dynamic leases, as they may only be
       used by the client to which they	are currently allocated.

THE FAILOVER PEER STATE	DECLARATION
       The state of any	failover peering arrangements is also recorded in  the
       lease file, using the failover peer statement:

       failover	peer name state	{
       my state	state at date;
       peer state state	at date;
       }

       The  states  of the peer	named name is being recorded.	Both the state
       of the running server (my state)	and the	other failover	partner	 (peer
       state)  are  recorded.	 The  following	 states	are possible: unknown-
       state, partner-down, normal, communications-interrupted,	resolution-in-
       terrupted, potential-conflict, recover, recover-done, shutdown, paused,
       and startup.

FILES
       DBDIR/dhcpd.leases DBDIR/dhcpd.leases~

SEE ALSO
       dhcpd(8),  dhcp-options(5),   dhcp-eval(5),   dhcpd.conf(5),   RFC2132,
       RFC2131.

AUTHOR
       dhcpd(8)	 was  written  by  Ted Lemon under a contract with Vixie Labs.
       Funding for this	project	was provided by	Internet  Systems  Consortium.
       Information   about  Internet  Systems  Consortium  can	be  found  at:
       https://www.isc.org/

							       dhcpd.leases(5)

NAME | DESCRIPTION | FORMAT | THE LEASE DECLARATION | THE FAILOVER PEER STATE DECLARATION | FILES | SEE ALSO | AUTHOR

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