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       dhcpd.leases - DHCP client lease database


       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/dhcp3/dhcpd.leases.   You can do this with:

            touch /var/lib/dhcp3/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 /var/lib/dhcp3/dhcpd.leases~.    Finally,
       the newly written lease database is moved into place.


       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.


       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  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 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.


       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.

       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  '|'

       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  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/dhcp3/dhcpd.leases


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


       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: