File dhcpd.leases

In case of system reboot or restart dhcpd to preserve information about the outstanding addresses, list of addresses that has already occupied stored in the file /var/db/dhcpd.leases. Before server will get address to a host, dhcpd writes it to the file, and rewrites the buffer to disk, that would guarantee the ptotection of information even with the case of an unexpected system crash. At startup, dhcpd server reads configuration file and when dhcpd processes the file dhcpd.leases to determine which addresses are free and which has been issued to clients. New value is recorded at the end of the lease file. 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 dhcpd.leases~ Finally, the newlywritten lease database is moved into place.

But there is a problem with the security of the system. If dhcpd process was forcibly stopped to the moment when the old file had been renamed and the new had not been moved into place yet, then after system reboot it will be no file /var/db/dhcpd.leases. In this situation system cannot start dhcpd daemon and it is required manual intervention. As a solution you might want to create an empty file. Never do this – thus you risk to lead system into an unstable state, and lose information about the previously assigned addresses. To solve the problem you should rename /var/db/dhcpd.leases~ to /var/db/dhcpd.leases, that will restore the previous state.

Дата добавления: 2015-08-27