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dhcpd.leases(5)						       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
       appears 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
       duration	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
       really 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
       appear 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
       indicate	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.

       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,
       respectively,  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-
       interrupted,  potential-conflict,  recover,   recover-done,   shutdown,
       paused, and startup.  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 | SEE ALSO | AUTHOR

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