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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  con-
     taining  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/db/dhcpd.leases.   You can do this with:

	  touch /var/db/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 database is cre-
     ated and all known leases are dumped to it.   Then, the old lease	database
     is  renamed /var/db/dhcpd.leases~.   Finally, the newly written lease data-
     base is moved into place.

FORMAT
     Lease descriptions are stored in a format that is parsed by the same recur-
     sive descent parser used to read  the  dhcpd.conf(5)  and	dhclient.conf(5)
     files.  Lease files can contain lease declarations, and also group and sub-
     group  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  declaration,  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;

     The start and end time of a lease are recorded using the  starts  and  ends
     statements.    The  tstp statement is specified if the failover protocol is
     being used, and indicates what time the peer has been told  the  lease  ex-
     pires.    The  tsfp statement is also specified if the failover protocol is
     being used, and indicates the lease expiry time that the peer has	acknowl-
     edged.   The date is specified 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 ex-
     pires  -  it's specified as a number from zero to six, with zero being Sun-
     day.  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 sec-
     ond 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 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  hexadecimal
     octets, separated by colons.

     uid client-identifier;

     The  uid  statement records the client identifier used by the client to ac-
     quire the lease.	Clients are not required to send client identifiers, 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 pro-
     tocol, 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) man-
     ual 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 bind-
     ing state will be either active or free.	The failover protocol adds  some
     additional  transitional  states,	as well as the backup state, which indi-
     cates that the lease is available for allocation 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 ex-
     pires 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 evaluations 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 general
     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	updating
     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 variable 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 variable
     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 statements
     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 '|' characters.

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,  poten-
     tial-conflict,   recover,	recover-done,  shutdown,  paused,  and	startup.
     /var/db/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.   Fund-
     ing for this project was provided by Internet Systems Consortium.	Informa-
     tion about Internet Systems Consortium can be found at: http://www.isc.org/

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