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.\" $OpenBSD: dhcpd.leases.5,v 1.2 1999/05/30 02:42:23 pjanzen Exp $
.\" dhcpd.conf.5
.\"
.\" Copyright (c) 1997 The Internet Software Consortium.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of The Internet Software Consortium nor the names
.\" of its contributors may be used to endorse or promote products derived
.\" from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
.\" CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
.\" CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" This software has been written for the Internet Software Consortium
.\" by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
.\" Enterprises. To learn more about the Internet Software Consortium,
.\" see ``http://www.isc.org/isc''. To learn more about Vixie
.\" Enterprises, see ``http://www.vix.com''.
.TH dhcpd.leases 5
.SH NAME
dhcpd.leases - DHCP client lease database
.SH 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
occurrence.
.PP
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.
.PP
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/db/dhcpd.leases~. Finally, the
newly written lease database is moved into place.
.PP
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 /var/db/dhcpd.leases. In this case, dhcpd will refuse to start,
and will require manual intervention. \fBDO NOT\fR 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
/var/db/dhcpd.leases~ to /var/db/dhcpd.leases, restoring the old, valid
lease file, and then start dhcpd. This guarantees that a valid lease
file will be restored.
.SH FORMAT
The format of the lease declarations is not currently documented.
.SH FILES
.B /var/db/dhcpd.leases
.SH SEE ALSO
dhcpd(8), dhcp-options(5), dhcpd.conf(5), RFC2132, RFC2131.
.SH AUTHOR
.B 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
.B http://www.isc.org/isc.
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