System Admin Q & A – IX

Ques 1: – How many WebLogic Servers can I have on a multi-cpu machine?

Ans: – There are many possible configurations and each has its own advantages and disadvantages. BEA WebLogic Server has no built-in limit for the number of server instances that can reside in a cluster. Large, multi-processor servers such as Sun Microsystems, Inc.

 Sun Enterprise 10000, therefore, can host very large clusters or multiple clusters. In most cases, WebLogic Server clusters scale best when deployed with one WebLogic Server instance for every two CPUs. However, as with all capacity planning, you should test the actual deployment with your target web applications to determine the optimal number and distribution of server instances. See Performance Considerations for Multi-CPU Machines for additional information.

Ques 2: – What happens when a failure occurs and the stub cannot connect to a Web Logic Server instance?

Ans: – When the failure occurs, the stub removes the failed server instance from its list. If there are no servers left in its list, the stubb uses DNS again to find a running server and obtain a current list of running instances. Also, the stub periodically refreshes its list of available server instances in the cluster, this allows the stub to take advantage of new servers as they are added to the cluster.

Ques 3: – What is the difference between an application server and a Web server?

Ans: – A Taking a big step back, a Web server serves pages for viewing in a Web browser, while an application server provides methods that client applications can call. A little more precisely, you can say that:

A Web server exclusively handles HTTP requests, whereas an application server serves business logic to application programs through any number of protocols.

Ques 4: – What does apachectl graceful do?

Ans: – It sends a SIGUSR1 for a restart, and starts the apache server if it?s not running.

Ques 5: – How do I configure Tomcat to work with IIS and NTLM?

Ans: – Follow the standard instructions for when the isapi_redirector.dll

Configure IIS to use “integrated windows security”

In server.xml, make sure you disable tomcat authentication:

<Connector port=”8009″ enableLookups=”false” redirectPort=”8443″ protocol=”AJP/1.3″ tomcatAuthentication=”false” />

Ques 6: – Explain the concepts of Tomcat Servlet Container ?

Ans: – A servlet container is a specialized web server that supports servlet execution.

* It combines the basic functionality of a web server with certain Java/servlet specific optimizations and extensions (such as an integrated Java runtime environment, and the ability to automatically translate specific URLs into servlet requests).
* Individual servlets are registered with a servlet container, providing the container with information such as the functionality, the URL used for identification.
* The servlet container then initializes the servlet as necessary and delivers requests to the servlet as they arrive.
* Many containers can dynamically add and remove servlets from the system, allowing new servlets to quickly be deployed or removed without affecting other servlets running from the same container.
* Servlet containers are also referred to as web containers or web engines.

Ques 6: – What is Virtualization ?

Ans: – Virtualization (or virtualisation), in computing, is the creation of a virtual (rather than actual) version of something, such as a hardware platform, operating system, a storage device or network resources.

Ques 7: – what are the key features of NFSv4 ?

Ans: – NFSv4 comes with several new features:

  • Advanced security management
  • Kerberos
  • SPKM
  • Firewall friendly
  • Advanced and aggressive cache management
  • Non Unix compatibility (Windows)
  • Easy to administer (Replication, migration)
  • Crash recovery (Client and server sides

Ques 8: – What are the types of hardware virtualization?

Ans: – Full virtualization: Almost complete simulation of the actual hardware to allow software, which typically consists of a guest operating system, to run unmodified Partial virtualization: Some but not all of the target environment is simulated. Some guest programs, therefore, may need modifications to run in this virtual environment.

Paravirtualization: A hardware environment is not simulated; however, the guest programs are executed in their own isolated domains, as if they are running on a separate system. Guest programs need to be specifically modified to run in this environment.

Ques 9: – What are the benefits of virtualization?

Ans: – Virtualization is a creation of virtual machines and to manage them from one place. It allows the resources to be shared with large number of network resources. Virtualization is having lots of benefits and they are as follows:

  • It helps in saving lots of cost and allows to easily maintaining it, in less cost.
  • It allows multiple operating systems on one virtualization platform.
  • It removes the dependency of heavy hardware to run the application.
  • It provides consolidating servers that are used for crashing of a server purpose
  • It reduces the amount of space being taken by data centers and company data.

Ques 10: – What is the location of postfix mailserver Queue ?

Ans: –By default, the Postfix mail queues are located in the /var/spool/postfix directory. Each message queue is created as a separate subdirectory within this directory. Each message is stored as a separate file in the subdirectory, using a unique identifier for the filename.

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