dhcpd.leases(5)

NAME
dhcpd.leases - DHCP client lease database

DESCRIPTION
The Internet Software Consortium DHCP Server keeps a persistent database of leases that it has assigned. This database is a free-form ASCII file containing one valid declaration per lease. If more than one declaration appears for a given lease, the last one in the file is used. The file is written as a log, so this is not an unusual occurrance.

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.

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.

There is a window of vulnerability where if the dhcpd process is killed or the system crashes after the old lease database has been renamed but before the new one has been moved into place, there will be no DBDIR/dhcpd.leases. In this case, dhcpd will refuse to start, and will require manual intervention. DO NOT simply create a new lease file when this happens - if you do, you will lose all your old bindings, and chaos will ensue. Instead, rename DBDIR/dhcpd.leases~ to DBDIR/dhcpd.leases, restoring the old, valid lease file, and then start dhcpd. This guarantees that a valid lease file will be restored.

FORMAT
The format of the lease declarations is not currently documented.

FILES
DBDIR/dhcpd.leases

SEE ALSO
dhcpd(8), dhcp-options(5), dhcpd.conf(5), RFC2132, RFC2131.

AUTHOR
dhcpd(8) was written by Ted Lemon <mellon@vix.com> under a contract with Vixie Labs. Funding for this project was provided by the Internet Software Corporation. Information about the Internet Software Consortium can be found at http://www.isc.org/isc.