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
       /var/lib/dhcpd/dhcpd.leases.   You can do this with:

	    touch /var/lib/dhcpd/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 /var/lib/dhcpd/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.  /var/lib/dhcpd/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)