Lease Database; Starting And Stopping The Server - Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual

For a complete list of option statements and what they do, refer to the dhcp-options man page.

21.2.2. Lease Database

On the DHCP server, the file /var/lib/dhcpd/dhcpd.leases stores the DHCP client lease
database. Do not change this file. DHCP lease information for each recently assigned IP address is
automatically stored in the lease database. The information includes the length of the lease, to whom
the IP address has been assigned, the start and end dates for the lease, and the MAC address of the
network interface card that was used to retrieve the lease.
All times in the lease database are in Coordinated Universal Time (UTC), not local time.
The lease database is recreated from time to time so that it is not too large. First, all known leases are
saved in a temporary lease database. The dhcpd.leases file is renamed dhcpd.leases~ and the
temporary lease database is written to dhcpd.leases.
The DHCP daemon could be killed or the system could crash after the lease database has
been renamed to the backup file but before the new file has been written. If this happens, the
dhcpd.leases file does not exist, but it is required to start the service. Do not create a new lease file.
If you do, all old leases are lost which causes many problems. The correct solution is to rename the
dhcpd.leases~ backup file to dhcpd.leases and then start the daemon.

21.2.3. Starting and Stopping the Server

Important
When the DHCP server is started for the first time, it fails unless the dhcpd.leases file
exists. Use the command touch /var/lib/dhcpd/dhcpd.leases to create the file if
it does not exist.
If the same server is also running BIND as a DNS server, this step is not necessary, as
starting the named service automatically checks for a dhcpd.leases file.
To start the DHCP service, use the command /sbin/service dhcpd start. To stop the DHCP
server, use the command /sbin/service dhcpd stop.
By default, the DHCP service does not start at boot time. To configure the daemon to start
automatically at boot time, refer to
If more than one network interface is attached to the system, but the DHCP server should only be
started on one of the interfaces, configure the DHCP server to start only on that device. In /etc/
sysconfig/dhcpd, add the name of the interface to the list of DHCPDARGS:
# Command line options here
DHCPDARGS=eth0
This is useful for a firewall machine with two network cards. One network card can be configured as a
DHCP client to retrieve an IP address to the Internet. The other network card can be used as a DHCP
server for the internal network behind the firewall. Specifying only the network card connected to the
internal network makes the system more secure because users can not connect to the daemon via the
Internet.
Chapter 16, Controlling Access to
Lease Database
Services.
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