Red Hat Enterprise Linux 64-Bit Support
Red Hat Enterprise Linux 6 supports 64-bit processors; these processors can theoretically use up to 18 exabytes of memory. As of general availability (GA), Red Hat Enterprise Linux 6 is tested and certified to support up to 8TB of physical memory.
The size of memory supported by Red Hat Enterprise Linux 6 is expected to grow over several minor updates, as Red Hat continues to introduce and improve more features that enable the use of larger memory blocks. Examples of such improvements (as of Red Hat Enterprise Linux 6 GA) are:
Huge pages and transparent huge pages
Non-Uniform Memory Access improvements
What Is Apache Hadoop?
The Apache™ Hadoop® project develops open-source software for reliable, scalable, distributed computing.
The Apache Hadoop software library is a framework that allows for the distributed processing of large data sets across clusters of computers using simple programming models. It is designed to scale up from single servers to thousands of machines, each offering local computation and storage. Rather than rely on hardware to deliver high-avaiability, the library itself is designed to detect and handle failures at the application layer, so delivering a highly-availabile service on top of a cluster of computers, each of which may be prone to failures.
The project includes these modules:
Hadoop Common: The common utilities that support the other Hadoop modules.
Hadoop Distributed File System (HDFS™): A distributed file system that provides high-throughput access to application data.
Hadoop YARN: A framework for job scheduling and cluster resource management.
Hadoop MapReduce: A YARN-based system for parallel processing of large data sets.
Unicast Addressing
Unicast delivery requires that a message should be addressed to a specific recipient. This is the most common type of messaging, so this addressing capability is present in almost all protocols.
Broadcast Addressing
Broadcasts are normally implemented via a special address that is reserved for that function. Whenever devices see a message sent to that address, they all interpret it as “This message goes to everyone.”
Multicast Addressing
Multicasts are the most complex type of message because they require a means of identifying a set of specific devices that will receive a message. It is often necessary to create several such groups, which may or may not partially overlap in their membership. Some mechanism is needed to manage which devices are in which groups.
Anycast message
A new type of message-addressing method was defined as part of IP version 6 (IPv6): the anycast message. This term identifies a message that should be sent to the closest member of a group of devices.
nmap - Network exploration tool and security / port scanner
Nmap (“Network Mapper”) is an open source tool for network exploration and security auditing. It was designed to rapidly scan large networks, although it works fine against single hosts. Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. While Nmap is commonly used for security audits, many systems and network administrators find it useful for routine tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.
A typical Nmap scan is shown in Example 1. The only Nmap arguments used in this example are -A, to enable OS and version detection,script scanning, and traceroute; -T4 for faster execution; and then the two target hostnames.
Example 1. A representative Nmap scan
# nmap -A -T4 scanme.nmap.org
Setting CPU affinity with taskset
taskset retrieves and sets the CPU affinity of a running process (by process ID). It can also be used to launch a process with a given CPU affinity, which binds the specified process to a specified CPU or set of CPUs. However, taskset will not guarantee local memory allocation.
CPU affinity is represented as a bitmask. The lowest-order bit corresponds to the first logical CPU, and the highest-order bit corresponds to the last logical CPU. These masks are typically given in hexadecimal, so that 0×00000001 represents processor 0, and 0×00000003 represents processors 0 and 1.
To set the CPU affinity of a running process, execute the following command, replacing mask with the mask of the processor or processors you want the process bound to, and pid with the process ID of the process whose affinity you wish to change.
To launch a process with a given affinity, run the following command, replacing mask with the mask of the processor or processors you want the process bound to, and program with the program, options, and arguments of the program you want to run.
Instead of specifying the processors as a bitmask, you can also use the -c option to provide a comma-delimited list of separate processors, or a range of processors, like so:
# taskset -c 0,5,7-9 — myprogram
Further information about taskset is available from the man page: man taskset and http://redhat.com/
