Your computer must
Run some variant of a UNIX® operating system.
Have a standard user-shell (e.g., sh(1), ksh(1), bash(1)) .
Have perl 5 installed.
Have the libxml2 development package installed (look for the file libxml2.a or libxml2.so and the file libxml/parser.h). This package is used by the LDM to parse the LDM registry. If this package's library is installed but not its header-file, then you must install the development package (the runtime package doesn't contain the necessary header-files).
Have the PNG development package installed (look for the file libpng.a or libpng.so and the file png.h). This is only necessary if you intend to ingest data via the LDM NOAAPORT system. If the PNG package's library is installed but not its header-file, then you must install the development package (the runtime package doesn't contain the necessary header-files).
Have the zlib development package installed (look for the file libz.a or libz.so and the file zlib.h). This package is used by the libxml2 package. If this package's library is installed but not its header-file, then you must install the development package (the runtime package doesn't contain the necessary header-files).
Have an accurate and monotonic clock.
The last requirement is absolutely necessary because the LDM protocol depends on accurate clocks on both the upstream host and the downstream host.
Additionally, if the clock is not monotonic (because it is periodically
set backwards by
ntpdate(8), for example) then processes
that read from the product-queue (such as upstream LDMs and pqacts will miss some data-products that are in
the queue. This is because data-products reside in the product-queue in
the order in which they were inserted into the queue according to
the system clock. If the system clock jumps backwards, then a
data-product might not be inserted at the tail
of the queue and so be missed by a process waiting at the tail
for the next product. The rate at which products will be missed
depends, among other things, on the rate at which products are inserted
into the queue, the frequency with which the system clock is adjusted
backwards, and the amount of the adjustments.
Linux systems with kernels older than 2.6.18 (for 32-bit systems) or 2.6.21 (for 64-bit systems) are at high-risk for non-monotonic system clocks.
This requirement can be generally satisfied by running a Network Time Protocol daemon (ntpd). The NTP daemon is available at ntp.org. Information on public NTP time servers is available at http://ntp.isc.org/bin/view/Servers/WebHome. Linux users with the older kernels mentioned above should pay particular attention to the NTP support documentation on Known Hardware Issues and Known Operating System Issues.
You may ignore this section if you install from a binary RPM file.
To install from source, you must have a UNIX® development-environment. In particular, your platform must have:
A Standard C compiler (e.g.,
A standard make(1) utility.
While every effort is made to ensure that the LDM source-code distribution can be compiled and installed on as wide a variety of UNIX® platforms as possible, we can, necessarily, only test on platforms that are available at the Unidata Program Center (UPC).
The UPC reserves the right to deny support to outdated or irregular platforms.