LDM Platform Requirements

Contents

• General Requirements
• Requirements for Installing from Source-Code

General Requirements

System Requirements

• Some variant of a UNIX operating system.
• Standard user-shell (e.g., sh(1), ksh(1), bash(1)).
• Sufficient local disk-space for the LDM product-queue, which can range from a few megabytes to many gigabytes in size depending on your data requirements.
• An accurate and monotonic clock.

The requirement for an accurate and monotonic clock 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 https://timetoolsltd.com/information/public-ntp-server/. 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.

Necessary Packages

The following items must be installed in order to build the LDM.

• perl 5 package
• zlib development package. Look for the file libz.a or libz.so and the file zlib.h. 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). This package is used by the libxml2 package.
• libxml2 development package. Look for the file libxml2.a or libxml2.so and the file libxml/parser.h. 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). This package is used by the LDM to parse the LDM registry.

Necessary for NOAAPort Ingestion

The following item is necessary in order to use the LDM to ingest data-products from the NOAAPort satellite broadcast system.

• PNG development package. Look for the file libpng.a or libpng.so and the file png.h. 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).

Performance Monitoring

The following utilities must be available in order to collect metrics on the performance of the LDM system via the command ldmadmin addmetrics.

• uptime
• vmstat
• netstat
• top

The following item is necessary to display the performance metrics of the LDM system via the command ldmadmin plotmetrics, or the plotMetrics utility.

• gnuplot package

Requirements for Installing from Source-Code

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., c89(1)).
• 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.