For QEMU/KVM, how to share data between host and guest

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General question for developers to access data between VM and VMM. As I know, paravirtualization solution is a good way to share data for VM and VMM since it has better performance. Please use Virtio 9p solution for QEMU/KVM. Note that you need to load 9p related modules for guest kernel. Add following in your
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How to add PHP DOMDocument extension to httpd in CentOS 7?

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Just migrated a PHP site to a new server. However, in /var/log/httpd/error_log, there are errors like [:error] [pid 2810] [client 61.92.242.24:43372] PHP Fatal error: Class ‘DOMDocument’ not found in /var/www/…/some.php on line 16 How to add PHP DOMDocument extension to httpd in CentOS 7? You need to install the package php-xml to have DOMCoument support
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Cannot start VM with error “no network with matching name ‘default'”

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I update libvirt version and want to start VM with the new libvirt tools but I failed as follows. > sudo virsh start kvm1 error: Failed to start domain kvm1 error: Network not found: no network with matching name ‘default’ It seems that the default ‘virbr0’ is missing after I update libvirt so I solve
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how change my policy of scheduling in hadoop?

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I want to change policy of scheduling in Hadoop, how to I can change job order in map reduce automatically. Assume you are using Hadoop 2 / YARN. The configuration parameter named yarn.resourcemanager.scheduler.class controls the class to be used as the resource scheduler for YARN/Hadoop. The default value for the scheduler class (check more at
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How to set the replication factor for one file when it is uploaded by `hdfs dfs -put` command line in HDFS?

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When uploading a file by the hdfs dfs -put command line in HDFS, how to set a replication factor instead of the global one for that file? For example, HDFS’s global replication factor is 3. For some temporary files, I would like to save just one copy for faster uploading and saving disk space. The
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How to add a new HDFS NameNode metadata directory to an existing cluster?

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We have a running HDFS cluster. Currently, the NameNode metadata data directory has only one directory configured in hdfs-site.xml: <property> <name>dfs.namenode.name.dir</name> <value>file:///home/hadoop/hdfs/</value> <description>NameNode directory for namespace and transaction logs storage.</description> </property> We would like to add a new directory for dfs.namenode.name.dir to make replicas of the metadata on a separated disk for higher data reliability.
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How to change number of replications of certain files in HDFS?

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The HDFS has a configuration in hdfs-site.xml to set the global replication number of blocks with the “dfs.replication” property. However, there are some “hot” files that are access by many nodes. How to increase the number of blocks for these certain files in HDFS? You can the replication number of certain file to 10: hdfs
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How to set the data replication factor of Hadoop HDFS?

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How to set the data replication factor of Hadoop HDFS in Hadoop 2 (YARN)? The default replication factor in HDFS is controlled by the dfs.replication property. The value is 3 by default. To change the replication factor, you can add a dfs.replication property settings in the hdfs-site.xml configuration file of Hadoop: <property> <name>dfs.replication</name> <value>1</value> <description>Replication
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Hadoop 2 (YARN) default configuration values

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Where to check the default Hadoop 2 (YARN) configuration values for: HDFS: hdfs-site.xml YARN: yarn-site.xml MapReduce: mapred-site.xml Default Hadoop 2 (YARN) configuration values for Hadoop 2.2.0 from Apache Hadoop website: HDFS: http://hadoop.apache.org/docs/r2.2.0/hadoop-project-dist/hadoop-hdfs/hdfs-default.xml YARN: https://hadoop.apache.org/docs/r2.2.0/hadoop-yarn/hadoop-yarn-common/yarn-default.xml MapReduce: https://hadoop.apache.org/docs/r2.2.0/hadoop-mapreduce-client/hadoop-mapreduce-client-core/mapred-default.xml

Question2answer: show excerpt in the RSS feed

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There is a “Include full text in feeds:” option in the “RSS feeds” configuration panel but no options/method to only show excerpt instead of the “full text” or nothing for RSS feeds. This need to hack the question2answer source code. Details are in the answer. The changes based on Question2asnwer 1.5.4: diff –git a/qa-include/qa-index.php b/qa-include/qa-index.php
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Disable WordPress Built-in Canonical URL link tag in HTML head

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The built-in canonical URL function since WordPress 2.9 is great. But under some situation, it is not needed. For example, all the Mingle Forum threads’ canonical URL is set to the URL of the page that contains the [mingleforum] shortcode, which, of course, is wrong. How to diabled it? We can disabled WordPress’s Built-in Canonical
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Spring Shell Technology For Java development

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This post is about the Spring Shell technology and its use in java. Experts of java development India have shared their best knowledge in this post for Spring Shell with the community people. If you have anything to ask, do it at the end. Technology: It is command line tool for Java applications to interact
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x-data-plane feature in QEMU/KVM

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Abstract In systems, sometimes, we use one global lock to keep synchronization among different threads. This principle also happens in QEMU/KVM (http://wiki.qemu.org/Main_Page) system. However, this may cause lock contention problem. The performance/scalability of whole system will be decreased. In order to solve this problem in QEMU/KVM, x-data-plane feature is designed/implemented, which the high-level idea is
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How to convert Managed Solution into Unmanaged for On-Premise CRM organisation?

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Solution is very important part of Dynamics CRM. In order to deploy your customization, solution is the only bridge which help you to achieve your goal. There are two types of solutions available in CRM: Managed and Unmanaged. Managed Solutions: This is the solutions that you can import and publish only. You neither export it nor you can
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Quartz Implementation in Java

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In this post, java development India based experts will explain the concept of Quartz. You will also learn the method of setting up the Quartz in this article. You can ask experts if anything bothers you. Technology Quartz is the open source Java technology for scheduling background jobs. If we want to execute the task
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Hadoop Installation Tutorial (Hadoop 2.x)

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Hadoop 2 or YARN is the new version of Hadoop. It adds the yarn resource manager in addition to the HDFS and MapReduce components. Hadoop MapReduce is a programming model and software framework for writing applications, which is an open-source variant of MapReduce designed and implemented by Google initially for processing and generating large data
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C++ Reference and Styles

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C++ References Reference of the C++ Language Library, with detailed descriptions of its elements and examples on how to use its functions: http://www.cplusplus.com/reference/ C++ reference: http://www.cppreference.com/w/ C++ Styles I compile a list of C++ styles on the Internet. http://geosoft.no/development/cppstyle.html http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml http://www.mactech.com/articles/develop/issue_02/C%2B%2B_Style_Guide_v007.html http://www.cs.uga.edu/~dkl/1302/Fall99/style.html

Speeding Up the Site With Apache GZIP Compression

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We can speed up the site with compression while save bandwidth at the same time. As most of the modern browsers support gzip encoding, we can set it up to let the users enjoy faster speed. The Apache mod_deflate is easy to set up and standard. It compress the content on the fly. We can
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