14. The LFC Process¶
kea-lfc is a service process that removes redundant information from
the files used to provide persistent storage for the Memfile database
backend. This service is written to run as a standalone process.
kea-lfc can be started externally, there is usually no need to
kea-lfc is run on a periodic basis by the Kea DHCP servers.
The process operates on a set of files, using them to receive input and output of the lease entries and to indicate what stage the process is in, in the event of an interruption. Currently the caller must supply names for all of the files.
14.2. Command-Line Options¶
kea-lfc is run as follows:
kea-lfc [-4 | -6] -c config-file -p pid-file -x previous-file -i copy-file -o output-file -f finish-file
-6 selects the protocol version of the lease
-c argument specifies the configuration file. This is required,
but is not currently used by the process.
-p argument specifies the PID file. When the
starts, it attempts to determine whether another instance of the process
is already running by examining the PID file. If one is already running,
the new process is terminated; if one is not running, Kea writes its PID
into the PID file.
The other filenames specify where the
kea-lfc process should look
for input, write its output, and perform its bookkeeping:
kea-lfcstarts, this is the result of any previous run of
kea-lfcfinishes, it is the result of this run. If
kea-lfcis interrupted before completing, this file may not exist.
input— before the DHCP server invokes
kea-lfc, it moves the current lease file here and then calls
kea-lfcwith this file.
output— This is the temporary file where
kea-lfcwrites the leases. Once the file has finished writing, it will be moved to the finish file (see below).
finish— This is another temporary file
kea-lfcuses for bookkeeping. When
kea-lfccompletes writing the output file, it moves the output to this file name. After
kea-lfcfinishes deleting the other files (previous and input), it moves this file to the previous lease file. By moving the files in this fashion, the
kea-lfcand the DHCP server processes can determine the correct file to use even if one of the processes were interrupted before completing its task.
There are several additional arguments, mostly for debugging purposes.
-d sets the logging level to debug.
-V print out
version stamps, with
-V providing a longer form.
-h prints out
the usage string.