Provided by: isc-dhcp-server_4.1.ESV-R4-0ubuntu5_i386 bug

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
       database  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
       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;
       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
       protocol 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
       hexadecimal 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
       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 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
       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 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
       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.

       The vendor-class-identifier variable

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

       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.

       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.

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)