Linux Bites !!!!

Red Hat Enterprise Linux 6 Technical Details

2011-12-13T20:19:00.000-08:00

Red Hat Enterprise Linux 6, the latest release of Red Hat's trusted datacenter platform, delivers advances in application performance, scalability, and security. With Red Hat Enterprise Linux 6, you can deploy physical, virtual, and cloud computing within your datacenter, reducing complexity, increasing efficiency, and minimizing administration overhead while leveraging technical skills and operational know-how. Red Hat Enterprise Linux 6 is an ideal platform to translate current and future technology innovations into the best value and scale for IT solutions.
Efficiency, Scalability, and Reliability
Scalability
Red Hat Enterprise Linux 6 supports more sockets, more cores, more threads, and more memory.
Efficient Scheduling
The CFS schedules the next task to be run based on which task has consumed the least time, task prioritization, and other factors. Using hardware awareness and multi-core topologies, the CFS optimizes task performance and power consumption.
Reliability, Availability, and Serviceability (RAS)
RAS hardware-based hot add of CPUs and memory is enabled.
When supported by machine check hardware, the system can recover from some previously fatal hardware errors with minimal disruption.
Memory pages with errors can be declared as "poisoned", and will be avoided.
Filesystems
The new default file system, ext4, is faster, more robust, and scales to 16TB.
The Scalable File System Add-On contains the XFS file system, which scales to 100TB.
The Resilient Storage Add-On includes the high availability, clustered GFS2 file system.
NFSv4 is significantly improved over NFSv3, and is backwards compatible.
Fuse allows filesystems to run in user space allowing testing and development on newer fused-based filesystems (such as cloud filesystems).
High Availability
The web interface based on Conga has been re-designed for added functionality and ease of use.
The cluster group communication system, Corosync, is mature, secure, high performance, and light-weight.
Nodes can re-enable themselves after failure without administrative intervention using unfencing.
Unified logging and debugging simplifies administrative work.
Virtualized KVM guests can be run as managed services which enables fail-over, including between physical and virtual hosts.
Centralized configuration and management is provided by Conga.
A single cluster command can be used to manage system logs from different services, and the logs have a consistent format that is easier to parse.
Power Management
The tickless kernel feature keeps systems in the idle state longer, resulting in net power savings.
Active State Power Management and Aggressive Link Power Management provide enhanced system control, reducing the power consumption of I/O subsystems. Administrators can actively throttle power levels to reduce consumption.
Realtime drive access optimization reduces filesystem metadata write overhead.
Unprecedented Resource Management
System Resource Allocation
Cgroups organize system tasks so that they can be tracked, and so that other system services can control the resources that cgroup tasks may consume (Partitioning). Two user-space tools, cgexec and cgclassify, provide easy configuration and management of cgroups.
Cpuset applies CPU resource limits to cgroups, allowing processing performance to be allocated across tasks.
The memory resource controller applies memory resource limits to cgroups.
The network resource controller applies network traffic limits to cgroups.
Storage
A snapshot of a logical volume may be merged back into the original logical volume, reverting changes that occurred after the snapshot.
Mirror logs of regions that need to be synchronized can be replicated, supporting high availability.
LVM hot spare allows the behavior of a mirrored logical volume after a device failure to be explicitly defined.
DM-Multipath allows paths to be dynamically selected based on queue size or I/O time data.
Very large SAN-based storage is supported.
Automated I/O alignment and self-tuning is supported.
Filesystem usage information is provided to the storage device, allowing administrators to use thin provisioning to allocate storage on-demand.
SCSI and ATA standards have been extended to provide alignment and I/O hints, allowing automated tuning and I/O alignment.
DIF/DIX provides better integrity checks for application data.
Networking
UDP Lite tolerates partially corrupted packets to provide better service for multimedia protocols, such as VOIP, where partial packets are better than none.
Multiqueue Networking increases processing parallelism for better performance from multiple processors and CPU cores.
Large Receive Offload (LRO) and Generic Receive Offload (GRO) aggregate packets for better performance.
Support for Data Center Bridging includes data traffic priorities and flow control for increased Quality of Service.
New support for software Fiber Channel over Ethernet (FCoE) is provided.
iSCSI partitions may be used as either root or boot filesystems.
IPv6 is supported.
Designed-In Security
Access Control
SELinux policies have been extended to more system services.
SELinux sandboxing allows users to run untrusted applications safely and securely.
File and process permissions have been systematically reduced whenever possible to reduce the risk of privilege escalation.
New utilities and system libraries provide more control over process privileges for easily managing reduced capabilities.
Walk-up kiosks (as in banks, HR departments, etc.) are protected by SELinux access control, with on-the-fly environment setup and take-down, for secure public use.
Openswan includes a general implementation of IPsec that works with Cisco IPsec.
Enforcement and Verification of Security Policies
OpenScap standardizes system security information, enabling automatic patch verification and system compromise evaluation.
Identity and Authentication
The new System Security Services Daemon (SSSD) provides centralized access to identity and authentication resources, enables caching and offline support.
OpenLDAP is a compliant LDAP client with high availability from N-way MultiMaster replication, and performance improvements.
Stable Application Development and Production Platform
Web Infrastructure
This release of Apache includes many improvements, see Overview of new features in Apache 2.2
A major revision of Squid includes manageability and IPv6 support
Memcached 1.4.4 is a high-performance and highly scalable, distributed, memory-based object caching system that enhances the speed of dynamic web applications.
Java
OpenJDK 6 is an open source implementation of the Java Platform Standard Edition (SE) 6 specification. It is TCK-certified based on the IcedTea project, and the implementation of a Java Web Browser plugin and Java web start removes the need for proprietary plugins.
Tight integration of OpenJDK and Red Hat Enterprise Linux includes support for Java probes in SystemTap to enable better debugging for Java.
Tomcat 6 is an open source and best-of-breed application server running on the Java platform. With support for Java Servlets and Java Server Pages (JSP), Tomcat provides a robust environment for developing and deploying dynamic web applications.
Development
Ruby 1.8.7 is included, and Rails 3 supports dependencies.
Version 4.4 of gcc includes OpenMP3 conformance for portable parallel programs, Integrated Register Allocator, Tuples, additional C++0x conformance implementations, and debuginfo handling improvements.
Improvements to the libraries include malloc optimizations, improved speed and efficiency for large blocks, NUMA considerations, lock-free C++ class libraries, NSS crypto consolidation for LSB 4.0 and FIPS level 2, and improved automatic parallel mode in the C++ library.
Gdb 7.1.29 improvements include C++ function, class, templates, variables, constructor / destructor improvements, catch / throw and exception improvements, large program debugging optimizations, and non-blocking thread debugging (threads can be stopped and continued independently).
TurboGears 2 is a powerful Internet-enabled framework that enables rapid web application development and deployment in Python.
Updates to the popular web scripting and programming languages PHP (5.3.2), Perl (5.10.1) include many improvements.
Application Tuning
SystemTap uses the kernel to generate non-intrusive debugging information about running applications.
The tuned daemon monitors system use and uses that information to automatically and dynamically adjust system settings for better performance.
SELinux can be used to observe, then tighten application access to system resources, leading to greater security.
Databases
PostgreSQL 8.4.4 includes many improvements, please see PostgreSQL 8.4 Feature Listfor details.
MySQL 5.1.47 improvement are listed here: What Is New in MySQL 5.1.
SQLite 3.6.20 includes significant performance improvements, and many important bug fixes. Note that this release has made incompatible changes to the internal OS interface and VFS layers (compared to earlier releases).
System API / ABI Stability
The Red Hat Enterprise Linux: Application Compatibility Specification document defines stable, public, system interfaces for the full ten-year life cycle of Red Hat Enterprise Linux 6. During that time, applications will not be affected by security errata or service packs, and will not require re-certification. Backward compatibility for the core ABI is maintained across major releases, allowing applications to span subsequent releases.
Integrated Virtualization
Kernel-Based Virtualization
The KVM hypervisor is fully integrated into the kernel, so all Red Hat Enterprise Linux system improvements benefit the virtualized environment.
The application environment is consistent for physical and virtual systems.
Deployment flexibility, provided by the ability to easily move guests between hosts, allows administrators to consolidate resources onto fewer machines during quiet times, or free up hardware for maintenance downtime.
Leverages Kernel Features
Hardware abstraction enables applications to move from physical to virtualized environments independently of the underlying hardware.
Increased scalability of CPUs and memory provides more guests per server.
Block storage benefits from selectable I/O schedulers and support for asynchronous I/O.
Cgroups and related CPU, memory, and networking resource controls provide the ability to reduce resource contention and improve overall system performance.
Reliability, Availability, and Serviceability (RAS) features (e.g., hot add of processors and memory, machine check handling, and recovery from previously fatal errors) minimize downtime.
Multicast bridging includes the first release of IGMP snooping (in IPv4) to build intelligent packet routing and enhance network efficiency.
CPU affinity assigns guests to specific CPUs.
Guest Acceleration
CPU masking allows all guests to use the same type of CPU.
SR-IOV virtualizes physical I/O card resources, primarily networking, allowing multiple guests to share a single physical resource.
Message signaled interrupts deliver interrupts as specific signals, increasing the number of interrupts.
Transparent hugepages provides significant performance improvements for guest memory allocation.
Kernel Same Page (KSM) provides reuse of identical pages across virtual machines (known as deduplication in the storage context).
The tickless kernel defines a stable time model for guests, avoiding clock drift.
Advanced paravirtualization interfaces include non-traditional devices such as the clock (enabled by the tickless kernel), interrupt controller, spinlock subsystem, and vmchannel.
Security
In virtualized environments, sVirt (powered by SELinux) protects guests from one another
Microsoft Windows Support
Windows WHQL-certified drivers enable virtualized Windows systems, and allow Microsoft customers to receive technical support for virtualized instances of Windows Server
Enterprise Manageability
Installation, Updates, and Deployment
Anaconda supports installation of a “minimal platform” as a specific server installation, or as a strategy for reducing the number of software packages to increase security.
Red Hat Network and Red Hat Network Satellite continue to provide management, provisioning, and monitoring for large deployments.
Installation options have been reorganized into “workload profiles” so that each system installation will provide the right software for specific tasks.
Dracut, a replacement for mkinitrd, minimizes the impact of underlying hardware changes, is more maintainable, and makes it easier to support third party drivers.
The new yum history command provides information about yum transactions, and supports undo and redo of selected operations.
Yum and RPM offer significantly improved performance.
RPM signatures use the Secure Hash Algorithm (SHA256) for data verification and authentication, improving security.
Storage devices can be designated for encryption at installation time, protecting user and system data. Key escrow allows recovery of lost keys.
Standards Based Linux Instrumentation for Manageability (SBLIM) manages systems using Web-Based Enterprise Management (WBEM).
ABRT enhanced error reporting speeds triage and resolution of software failures.
Routine Task Delegation
PolicyKit allows administrators to provide users access to privileged operations, such adding a printer or rebooting a desktop, without granting administrative privileges.
Printing
Improvements include better printing, printer discovery, and printer configuration services from cups and system-config-printer.
SNMP-based monitoring of ink and toner supply levels and printer status provides easier monitoring to enable efficient inventory management of ink and toner cartridges.
Automatic PPD configuration for postscript printers, where PPD option values are queried from printer, are available in CUPS web interface.
Microsoft Interoperability
Samba improvements include support for Windows 2008R2 trust relationships: Windows cross-forest, transitive trust, and one-way domain trust.
Applications can use OpenChange to gain access to Microsoft Exchange servers using native protocols, allowing mail clients like Evolution to have tighter integration with Exchange servers.

Info Source : http://www.redhat.com/rhel/server/details/

History command

2011-12-06T00:06:00.001-08:00

Use inbuilt variable HISTTIMEFORMAT to set the values as shown below

#export HISTTIMEFORMAT='%F %T '

%F for setting year/month/day

%T for setting time

now try to execute history command to see the difference

#history

sample output

500  2011-03-16 17:06:09 exit
 501  2011-03-16 17:06:14 apt-get install tree
 502  2011-03-16 17:06:36 tree 
 503  2011-03-16 17:06:54 man tree
 504  2011-03-16 17:07:02 tree -d
 505  2011-03-16 17:07:07 tree

If you restart/logout from machine will this setting available to you?

A simple answer for this is no. Then how can we make it permanent?

Just append this variable to .bash_profile for every user.

echo "export HISTTIMEFORMAT='%F %T '" >> ~/.bash_profile

How about setting this value to the new user which are going to be created on the machine?

export it to /etc/profile file

echo "export HISTTIMEFORMAT='%F %T '" >> /etc/profile

Redhat Desktop versions comparison chart

2011-11-26T03:43:00.001-08:00

	Version 4		Version 5			Version 6
	Workstation	Desktop	Desktop	Desktop with Workstation option	Desktop with Multi OS option	Workstation	Client
Desktop Architecture support
X86, AMD64, Intel64	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Itanium2	Yes	No	No	No	No	No	No
Desktop Support limits as defined by Red Hat Enterprise Linux Product Subscription
Maximum physical CPUs/sockets [1]	2	1	1	2	1	2	1
Maximum memory	Unlimited	4GB	4GB	Unlimited	4GB	Unlimited	8GB
Maximum virtualized guests/instances [2]	N/A	N/A	N/A	N/A	4	1	1
Storage virtualization (with Red Hat GFS and Cluster Suite)	N/A	N/A	No	No	No	No	No
Included Red Hat Network modules	Update Module	Update Module	Update, Management, & Provisioning modules			Update, Management, & Provisioning modules

Notes:

[1] Red Hat defines physical CPUs equivalently to sockets, so a multi-core and/or hyperthreading CPU is counted as a single socket when determining which subscription to purchase

[2] Using the virtualization technology included with Red Hat Enterprise Linux

from,

http://www.redhat.com/rhel/desktop/compare/

Redhat Server versions comparison chart

2011-11-26T03:42:00.001-08:00

	Version 3		Version 4		Version 5		Version 6
	AS	ES	AS	ES	Advanced Platform	Server
Server Architecture support
x86, AMD64, Intel64	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Itanium	Yes	Yes	Yes	Yes	Yes	Yes	No
IBM POWER	Yes	No	Yes	No	Yes	Yes	Yes
IBM Mainframe	Yes	No	Yes	No	No	Yes	Yes
Server Support limits as defined by Red Hat Enterprise Linux Product Subscription
Maximum physical CPUs/sockets [1]	Unlimited	2	Unlimited	2	Unlimited	2	Varies per Subscription
Maximum memory	Unlimited	8GB	Unlimited	16GB	Unlimited	Unlimited	Unlimited
Maximum virtualized guests/instances [2]	N/A	N/A	N/A	N/A	Unlimited	4	1/4/unlimited (varies per subscription)
Storage virtualization (with Red Hat GFS and Cluster Suite)	N/A	N/A	N/A	N/A	Yes	No	Optional
Included Red Hat Network modules	Update Module	Update Module	Update Module	Update Module	Update Module	Update Module	Update Module

Notes:

[1] Red Hat defines physical CPUs equivalently to sockets, so a multi-core and/or hyperthreading CPU is counted as a single socket when determining which subscription to purchase

[2] Using the virtualization technology included with Red Hat Enterprise Linux

from ,

http://www.redhat.com/rhel/server/compare/

Red Hat Enterprise Linux Technology capabilities and limits

2011-11-26T03:41:00.001-08:00

	Version 3	Version 4	Version 5	Version 6
Maximum logical CPUs [2]
x86	16	32	32	32
Itanium2	8	256/512	256/1024	N/A [6]
X86_64	8	64/64	160/255	160/4096
POWER	8	64/128	128/128	128
System z	32 (z900)	64 (z10 EC)	80 (z196)	80 (z196)
Maximum memory [5]
X86	64GB [3]	64GB [3]	16GB [4]	16GB [4]
Itanium2	128GB	2TB	2TB	N/A [6]
X86_64	128GB	256GB/1TB	1TB	2TB/64TB
POWER	64GB	128GB/1TB	512GB/1TB	2TB
System z	256GB (z900)	1.5TB (z10 EC)	3TB (z196)	3TB (z196)
Required minimums
X86	256MB	256MB	512MB minimum/ 1 GB/logical CPU recommended	512MB minimum/ 1 GB/logical CPU recommended
X86_64	256MB	256MB	512MB/ 1 GB/logical CPU recommended	1GB minimum/ 1 GB/logical CPU recommended
Itanium2	512MB	512MB	512MB/ 1 GB/logical CPU recommended	N/A [6]
POWER	512MB	512MB	1GB minimum/ 2GB recommended	2GB minimum/ 2GB required per install
Minimum diskspace	800MB	800MB	1GB minimum/ 5GB recommended	1GB minimum/ 5GB recommended
Filesystems and Storage Limits
Maximum filesize (Ext3)	2TB	2TB	2TB	2TB
Maximum filesystem size (Ext3)	2TB	8TB	16TB	16TB
Maximum filesize (Ext4)	--	--	16TB	16TB
Maximum filesystem size (Ext4)	--	--	16TB	16TB
Maximum filesize (GFS)	2TB	16TB/8EB	16TB/8EB [7]	N/A
Maximum filesystem size (GFS)	2TB	16TB/8EB	16TB/8EB [7]	N/A
Maximum filesize (GFS2)	--	--	25TB	100TB
Maximum filesystem size (GFS2)	--	--	25TB	100TB
Maximum filesize (XFS)	--	--	100TB	100TB
Maximum filesystem size (XFS)	--	--	100TB	100TB
Maximum Boot LUN size (BIOS)	--	--	<2TB	<2TB [10]
Maximum Boot LUN size (UEFI)	--	--	NA	Any [10]
Maximum x86 per-process virtual address space	Approx 4GB	Approx 4GB	Approx 3GB [4]	Approx 3GB [4]
Maximum x86_64 per-process virtual address space		512GB	2TB	128TB
Kernel and OS features
Kernel foundation	Linux 2.4.21	Linux 2.6.9	Linux 2.6.18	2.6.32 - 2.6.34
Compiler/toolchain	GCC 3.2	GCC 3.4	GCC 4.1	GCC 4.4
Languages supported	10	15	19	22
NIAP/CC certified [11]	Yes (3+)	Yes (4+)	Yes (4+)	Under Evaluation
Common Criteria certified KVM [11]	--	--	Under Evaluation	Under Evaluation
IPv6	--	--	Ready Logo Phase-II	Under Evaluation
Compatibility libraries	V2.1	V2.1 and V3	V3 and V4	V4 and V5
FIPS certified [11]	--	--	Yes	Under Evaluation
Common Operating Environment (COE) compliant	Yes	Yes	N/A	N/A
LSB compliant	Yes - 1.3	Yes - 3	Yes - 3.1	Under Evaluation
GB18030	No	Yes	Yes	Yes
Client environment
Desktop GUI	Gnome 2.2	Gnome 2.8	Gnome 2.16	Gnome 2.28
Graphics	XFree86	X.org	X.org 7.1.1	X.org 7.4
OpenOffice	V1.1	V1.1.2	V2.0.4 [12]	V3.2 [12]
Gnome Evolution	V1.4	V2.0	V2.8.0	V2.28
Default browser	Mozilla	Firefox	Firefox 1.5 [12]	Firefox 3.6 [12]

Notes:

[1] Supported limits reflect the current state of system testing by Red Hat and its partners for mainstream hardware. Systems exceeding these supported limits may be included in the Hardware Catalog after joint testing between Red Hat and its partners. If they exceed the supported limits posted here, entries in the Hardware Catalog will include a reference to the details of the system specific limits, and are fully supported. In addition to supported limits reflecting hardware capability, there may be additional limits under the Red Hat Enterprise Linux subscription terms. Supported limits are subject to change as on-going testing completes.

[2] Red Hat defines a logical CPU as any schedulable entity. So every core/thread in a multi-core/thread processor is a logical CPU

[3] The "SMP" kernel supports a maximum of 16GB of main memory. Systems with more than 16GB of main memory use the "Hugemem" kernel. In certain workload scenarios it may be advantageous to use the "Hugemem" kernel on systems with more than 12GB of main memory.

[4] The x86 "Hugemem" kernel is not provided in Red Hat Enterprise Linux 5 or 6.

[5] The architectural limits are based on the capabilities of the RHEL kernel and the physical hardware. RHEL 6 limit is based on 46-bit physical memory addressing. RHEL 5 limit is based on 40-bit physical memory addressing. All system memory should be balanced across NUMA nodes in a NUMA capable system.

[6] Red Hat Enterprise Linux 6 does not include support for the Itanium 2 architecture.

[7] If there are any 32-bit machines in the cluster, the maximum gfs file system size is 16TB. If all machines in the cluster are 64-bit, the maximum size is 8EB.

[8] Officially support 125 CPUs across the entire machine.

[9] Requires Intel EPT and AMD RVI technology support

[10] UEFI and GPT support required for more that 2TB boot LUN support (https://access.redhat.com/kb/docs/DOC-16981)

[11] Security certification details are available at: http://www.redhat.com/solutions/government/certifications/

[12] Firefox, Thunderbird, and OpenOffice applications will be updated during the lifecycle

From ,

http://www.redhat.com/rhel/compare/

Red Hat Enterprise Linux

2011-11-26T03:30:00.000-08:00

Red Hat Enterprise Linux: Hey, check out this page I saw on redhat.com.

CD Burning

2011-11-25T04:05:00.001-08:00

cdrecord -scanbus to find out the SCSI ID X,Y,Z of your burner (usually 0,0,0)
cdrecord -v dev=0,0,0 blank=fast to fast blank a CD-RW
cdrecord -v dev=0,0,0 blank=all to thoroughly blank a CD-RW
mkisofs -v -J -r -o mysrcdir.iso mysrcdir to create an ISO image of all files in directory mysrcdir
mount -t iso9660 -o ro,loop mysrcdir.iso /mnt/cdrom to check that the ISO image is OK before burning
mkisofs -v dev=0,0,0 speed=10 -data mysrcdir.iso to burn ISO image at 10x speed
cdrecord -dummy ... will do a dummy write for testing
cdrecord driveropts=burnproof will turn on 'burnproof' settings
mkisofs -v -J -r . | cdrecord -v driveropts=burnproof speed=10 dev=0,0,0 - will avoid creating an intermediate ISO image
mount /mnt/cdrom to mount the CD
cdrecord -v speed=10 dev=0,0,0 -pad -audio *.wav will burn an audio CD of .wav files

Adding New TrueType fonts

2011-11-25T04:04:00.001-08:00

Make a new directory, say /usr/X11R6/lib/X11/fonts/MyTTFdir
Copy your .ttf font files into there
cd /usr/X11R6/lib/X11/fonts/MyTTFdir
ttmkfdir to make the fonts.scale file
mkfontdir to make the fonts.dir file (needed for TTF fonts?)
chkfontpath --add=/usr/X11R6/lib/X11/fonts/MyTTFdir (or manually by editing /etc/X11/fs/config)
service xfs restart (or /etc/init.d/xfs restart)
chkfontpath --list to see if MyTTFdir was added
xfontsel to browse/view available fonts

How to download youtube viedos in linux (Ubuntu) (apt-get install youtube-dl)

2011-11-25T03:49:00.001-08:00

youtube-dl

Download youtube viedos from linux ubuntu machine
Install apt-get install youtube-dl

Step 1:- open terminal Window.
Step 2:- Type apt-get install youtube-dl and enter.
Step 3:- After Enter the above command it downloads some package and will it Install automatically.
Step 4:- After finishing installation.
Step 5:- Type syntax youtube-dl
Step 6:- Its start to download youtube movie.

Booting Process in Linux

2011-11-25T03:38:00.001-08:00

who are responsible for the booting process.
        1.BIOS(Basic Input/Output System)
        2.MBR(Master Boot Record)
        3.LILO or GRUB
             LILO:-LInux LOader
             GRUB:-GRand Unified Bootloader
        4.Kernel
        5.init
        6.Run Levels
1.BIOS:
      i.When we power on BIOS performs a Power-On Self-Test (POST) for all of the different hardware components in the system to make sure everything is working properly
     ii.Also it checks for whether the computer is being started from an off position (cold boot) or from a restart (warm boot) is
stored at this location.
     iii.Retrieves information from CMOS (Complementary Metal-Oxide Semiconductor) a battery operated memory chip on the motherboard that stores time, date, and critical system information.
     iv.Once BIOS sees everything is fine it will begin searching for an operating system Boot Sector on a valid master boot sector
on all available drives like hard disks,CD-ROM drive etc.
     v.Once BIOS finds a valid MBR it will give the instructions to boot and executes the first 512-byte boot sector that is the first
sector (“Sector 0″) of a partitioned data storage device such as hard disk or CD-ROM etc .
2.MBR

     i. Normally we use multi-level boot loader.Here MBR means I am referencing to DOS MBR.
     ii.Afer BIOS executes a valid DOS MBR,the DOS MBR will search for a valid primary partition marked as bootable on the hard disk.
     iii.If MBR finds a valid bootable primary partition then it executes the first 512-bytes of that partition which is second level MBR.
     iv. In linux we have two types of the above mentioned second level MBR known as LILO and GRUB
3.LILO
     i.LILO is a linux boot loader which is too big to fit into single sector of 512-bytes.
     ii.So it is divided into two parts :an installer and a runtime module.
     iii.The installer module places the runtime module on MBR.The runtime module has the info about all operating systems installed.
     iv.When the runtime module is executed it selects the operating system to load and transfers the control to kernel.
     v.LILO does not understand filesystems and boot images to be loaded and treats them as raw disk offsets
GRUB
     i.GRUB MBR consists of 446 bytes of primary bootloader code and 64 bytes of the partition table.
     ii.GRUB locates all the operating systems installed and gives a GUI to select the operating system need to be loaded.
     iii.Once user selects the operating system GRUB will pass control to the karnel of that operating system.
see below what is the difference between LILO and GRUB
4.Kernel
     i.Once GRUB or LILO transfers the control to Kernel,the Kernels does the following tasks

Intitialises devices and loads initrd module
mounts root filesystem

5.Init
     i.The kernel, once it is loaded, finds init in sbin(/sbin/init) and executes it.
     ii.Hence the first process which is started in linux is init process.
     iii.This init process reads /etc/inittab file and sets the path, starts swapping, checks the file systems, and so on.
     iv.It runs all the boot scripts(/etc/rc.d/*,/etc/rc.boot/*)
     v.starts the system on specified run level in the file /etc/inittab
6.Runlevel
     i.There are 7 run levels in which the linux OS runs and different run levels serves for different purpose.The descriptions are
given below.

0 – halt
1 – Single user mode
2 – Multiuser, without NFS (The same as 3, if you don’t have networking)
3 – Full multiuser mode
4 – unused
5 – X11
6 – Reboot

ii.We can set in which runlevel we want to run our operating system by defining it on /etc/inittab file.
Now as per our setting in /etc/inittab the Operating System the operating system boots up and finishes the bootup process.
Below are given some few important differences about LILO and GRUB

LILO	GRUB
LILO has no interactive command interface	GRUB has interactive command interface
LILO does not support booting from a network	GRUB does support booting from a network
If you change your LILO config file, you have to rewrite the LILO stage one boot loader to the MBR	GRUB automatically detects any change in config file and auto loads the OS
LILO supports only linux operating system	GRUB supports large number of OS

Redhat History

2011-11-25T03:16:00.001-08:00

1968

ARPANET founded. The precursor to the Internet, it allows researchers to share code and information.

1969

Ken Thompson, researcher at Bell Labs, writes the first version of Unix.

1979

AT&T announces plans to commercialize Unix.

1983

Richard Stallman establishes the Free Software Foundation at MIT. The GNU project to construct an operating system based on Unix but for which the source code is freely available, begins. Stallman also establishes the idea of "copyleft" and the General Public License (GPL).

1987

Andrew Tanenbaum releases Minix, a version of Unix for the PC, Mac, Amiga, and Atari ST. Source code included.

1989

Michael Tiemann (Red Hat Vice President, Open Source Affairs) co-founds Cygnus Solutions, the first business to provide custom engineering and support services for free software.

1991

Linus Torvalds releases the Linux kernel.

Bob Young introduced to free software and UNIX by the system administrators of the New York City UNIX Users Group (Unigroup).

1993

Young incorporates ACC Corporation, a catalog business that sells Linux and Unix software accessories and books and distributes a magazine called New York UNIX

1994

Marc Ewing creates his own distribution of Linux which he names Red Hat Linux. Released in October, it becomes known as the Halloween release.

1995

Young buys Ewing's business, merges it with ACC Corporation, and names the new company Red Hat Software.

Red Hat Linux 2.0 is released, officially unveils the new package management system called RPM.

1996

Red Hat opens sales and administration functions to North Carolina, opens corporate headquarters in Durham.

Distance Education in INDIA - MBA|B.Com|M.Tech|B.Tech

2011-11-07T04:14:00.000-08:00

Linux shell Comparison table

2011-11-06T01:42:00.000-07:00

Linux Some Basic Commands

2011-11-06T01:09:00.000-07:00

Process

ps -auwx - Report a snapshot of the current processes

pstree - Display a tree of processes

pmap - Display/examine memory map and libraries

pidof processname - Find the process ID of a running program

pgrep processname - Look up or signal processes based on name and other attributes

ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10

Performance

iostat - Report Central Processing Unit (CPU) statistics and input/output statistics for devices and partitions

vmstat - Report virtual memory statistics

mpstat - Report processors related statistics

netstat - Print network connections, routing tables, interface statistics, masquerade connections and multicast memberships

free - Display amount of free and used memory in the system

top - provides a dynamic real-time view of a running system

slabtop - display kernel slab cache information in real time

sar - Collect, report, or save system activity information

General Info

uname - print system information

uptime - Tell how long the system has been running

cat /proc/meminfo - Show memory size and usage

runlevel - find the current and previous system runlevel

chkconfig - updates and queries runlevel information for system services

ntsysv - simple interface for configuring runlevels

init, telinit - process control initialization

w - Displays currently logged in users and processes they are running

who - show who is logged on

whoami - Displays user id

chsh - change your login shell

/etc/shells is a text file which contains the full pathnames of valid login shells

set - Display all environment variables in your current environment

id - Display user and all group ids

last, lastb - Listing of most recent logins by users.command

history - Shell command to display previously entered commands

sysreport - collect some detailed information about the hardware which will be used to diagnose problems with the system

hostname - show or set the systemâs host name

domainname - show or set the systemâs NIS/YP domain name

dnsdomainname - show the systemâs DNS domain name

nisdomainname - show or set systemâs NIS/YP domain name

ypdomainname - show or set the systemâs NIS/YP domain name

Kernel

ipcs - List share queues, Shared memory, List Semaphores.

cat /proc/modules List all currently loaded kernel modules.

lsmod - List loaded modules

insmod - Inserts a module into the active kernel

rmmod - Remove a loaded module. Just specify the module name. No ".o" or path necessary.

modprobe - High level handling of loadable modules. Loads module and dependencies.

depmod - Creates dependencies file for a module (used by modprobe)

modinfo - Display information about a kernel module

sysctl - configure kernel parameters at runtime

Network

ifconfig - configure a network interface

setting in /etc/sysconfig/network. Command will change entry in /etc/hosts

mii-tool - view, manipulate media-independent interface status

ethtool - Display or change ethernet card settings

route - show / manipulate the IP routing table

Filesystem

proc - process information pseudo-filesystem

fstab - static information about the filesystems

fsck - check and repair a Linux file system

df - report filesystem disk space usage

du - estimate file space usage

mount - mount a file system

umount - unmount file systems

fdisk - Partition table manipulator for Linux

lsof filesystem - list open files

fuser - identify processes using files or sockets

e2label - Change the label on an ext2/ext3 filesystem

mkfs -t ext2 /dev/ram - build a Linux file system

mke2fs - create an ext2/ext3 filesystem

e2fsck - check a Linux ext2/ext3 file system

tune2fs - adjust tunable filesystem parameters on ext2/ext3 filesystems

dumpe2fs - dump ext2/ext3 filesystem information

partprobe - inform the OS of partition table changes

mkswap - set up a Linux swap area

swapon, swapoff - enable/disable devices and files for paging and swapping

NFS

exportfs - maintain list of NFS exported file systems

showmount - show mount information for an NFS server

nfsstat - print NFS statistics

Files

ls - List directory contents. List file information

fuser - Identify processes using files or sockets

file - Identify file type.

File permission

chmod - Change a file's mode or permissions

umask - Set default file permissions

chgrp - Change a file's group

chown - Change a file's owner

chroot - run command or interactive shell with special root directory

ACL

setfacl - set file access control lists

chacl - change the access control list of a file or directory

getfacl - get file access control lists

User

useradd - Create a new user or update default new user information

usermod - Modify a user account

userdel - Delete a user account and related files

passwd - update a userâs authentication tokens(s)

finger - user information lookup program

chfn - change your finger information

chage - change user password expiry information

users - Show all users logged in.

Group

groupadd - Create a new group

groupmod - Modify a group

groupdel - Delete a group

newgrp - log in to a new group

gpasswd - administer the /etc/group file

grpck - verify integrity of group files

groups - Display groups you are part of

Hardware Info

/usr/bin/lsdev - List devices and info on system hardware. Also IRQ's.(RPM package procinfo)

/sbin/lspci - List all PCI devices (result of probe) Also lspci -vvx and cat /proc/pci

cat /proc/interrupts - List IRQ's used by system and the device using the interrupt.

cat /proc/ioports - List I/O ports used by system.

cat /proc/dma - List DMA channels and device used by system.

cat /proc/cpuinfo - List info about CPU.

hdparm -I /dev/hda - get Harddisk info

Debugging

kill - terminate a process

killall - kill processes by name

pkill - will send the specified signal (by default SIGTERM) to each process instead of listing them on stdout

nice - run a program with modified scheduling priority

renice - alter priority of running processes

ulimit

Log files

closelog, openlog, setlogmask, syslog - control system log

/var/log/messages - system messages

/secure - Logging by PAM of network access attempts

/dmesg - Log of system boot. Also see command dmesg

/boot.log - Log of system init process

/xferlog.1 - File transfer log

/lastlog - Requires the use of the lastlog command to examine contents

/maillog - log from sendmail daemon

Redhat Certification

2011-11-06T01:00:00.000-07:00

Source : http://www.redhat.com/certification/

RHCSA

Understand and Use Essential Tools

Access a shell prompt and issue commands with correct syntax
Use input-output redirection (>, >>, |, 2>, etc.)
Use grep and regular expressions to analyze text
Access remote systems using ssh and VNC
Log in and switch users in multi-user runlevels
Archive, compress, unpack and uncompress files using tar, star, gzip, and bzip2
Create and edit text files
Create, delete, copy and move files and directories
Create hard and soft links
List, set and change standard ugo/rwx permissions
Locate, read and use system documentation including man, info, and files in /usr/share/doc .
[Note: Red Hat may use applications during the exam that are not included in Red Hat Enterprise Linux for the purpose of evaluating candidate's abilities to meet this objective.]

Operate Running Systems

Boot, reboot, and shut down a system normally
Boot systems into different runlevels manually
Use single-user mode to gain access to a system
Identify CPU/memory intensive processes, adjust process priority with renice, and kill processes
Locate and interpret system log files
Access a virtual machine's console
Start and stop virtual machines
Start, stop and check the status of network services

Configure Local Storage

List, create, delete and set partition type for primary, extended, and logical partitions
Create and remove physical volumes, assign physical volumes to volume groups, create and delete logical volumes
Create and configure LUKS-encrypted partitions and logical volumes to prompt for password and mount a decrypted file system at boot
Configure systems to mount file systems at boot by Universally Unique ID (UUID) or label
Add new partitions, logical volumes and swap to a system non-destructively

Create and Configure File Systems

Create, mount, unmount and use ext2, ext3 and ext4 file systems
Mount, unmount and use LUKS-encrypted file systems
Mount and unmount CIFS and NFS network file systems
Configure systems to mount ext4, LUKS-encrypted and network file systems automatically
Extend existing unencrypted ext4-formatted logical volumes
Create and configure set-GID directories for collaboration
Create and manage Access Control Lists (ACLs)
Diagnose and correct file permission problems

Deploy, Configure and Maintain Systems

Configure networking and hostname resolution statically or dynamically
Schedule tasks using cron
Configure systems to boot into a specific runlevel automatically
Install Red Hat Enterprise Linux automatically using Kickstart
Configure a physical machine to host virtual guests
Install Red Hat Enterprise Linux systems as virtual guests
Configure systems to launch virtual machines at boot
Configure network services to start automatically at boot
Configure a system to run a default configuration HTTP server
Configure a system to run a default configuration FTP server
Install and update software packages from Red Hat Network, a remote repository, or from the local filesystem
Update the kernel package appropriately to ensure a bootable system
Modify the system bootloader
Configure a system to run a default configuration NTP server and synchronize time using other NTP peers

Manage Users and Groups

Create, delete, and modify local user accounts
Change passwords and adjust password aging for local user accounts
Create, delete and modify local groups and group memberships
Configure a system to use an existing LDAP directory service for user and group information

Manage Security

Configure firewall settings using system-config-firewall or iptables
Set enforcing and permissive modes for SELinux
List and identify SELinux file and process context
Restore default file contexts
Use boolean settings to modify system SELinux settings
Diagnose and address routine SELinux policy violations

RHCE

System Configuration and Management

Route IP traffic and create static routes
Use iptables to implement packet filtering and configure network address translation (NAT)
Use /proc/sys and sysctl to modify and set kernel run-time parameters
Configure system to authenticate using Kerberos
Configure a system as an iSCSI initiator that persistently mounts an iSCSI target
Produce and deliver reports on system utilization (processor, memory, disk, and network)
Use shell scripting to automate system maintenance tasks
Configure a system to log to a remote system
Configure a system to accept logging from a remote system

Network Services

Network services are an important subset of the exam objectives. RHCE candidates should be capable of meeting the following objectives for each of the network services listed below:

Install the packages needed to provide the service
Configure SELinux to support the service
Configure the service to start when the system is booted
Configure the service for basic operation
Configure host-based and user-based security for the service

RHCE candidates should also be capable of meeting the following objectives associated with specific services:

HTTP/HTTPS

Configure a virtual host
Configure private directories
Deploy a basic CGI application
Configure group-managed content

DNS

Configure a caching-only name server
Configure a caching-only name server to forward DNS queries
Note: Candidates are not expected to configure master or slave name servers

FTP

Configure anonymous-only download

NFS

Provide network shares to specific clients
Provide network shares suitable for group collaboration

SMB

Provide network shares to specific clients
Provide network shares suitable for group collaboration

SMTP

Configure a mail transfer agent (MTA) to accept inbound email from other systems
Configure an MTA to forward (relay) email through a smart host

SSH

Configure key-based authentication
Configure additional options described in documentation

Total Bank Details in India

2011-10-11T05:57:00.000-07:00

Total Bank Details in India : http://indian-banks.info/

Indian government totally online

2011-10-11T05:55:00.001-07:00

7 Income Tax saving tips you might not know

2011-10-11T05:54:00.001-07:00

Haven’t you gotten bored of regular tax saving tips? Are you looking for some tips which are different, kinda unique and not very well known? If yes, then you’re reading the right article, mate! I will share some tips which would help you in area of tax saving. Some of these tips will help you in this, current year and some, at some later point. But helpful at some level, they will be . Let’s look at them.
1. Gift money to your major children and Save tax on Future Income
Imagine this, you have Rs 25 lacs. Logically you put this in a fixed deposit or invest in some other financial product through which you get an interest at 8%. You will get Rs 2 lacs as interest which will be added to your income and you pay tax on this income. Not good!
Now what? How do we save tax on these 2 lacs? As per income-tax laws you can gift any amount of money to your major children without attracting gift-tax and as their money will become theirs any income arising out of it would be treated as their income, not yours. In case their income is below the limits, there won’t be any tax.
However there can be times, where you might not feel too comfortable gifting away large amounts of money to your major children, in which case, there is another option of giving them loans. And guess what? you can make interest-free loans to your major children as per the law . Please note that doing exactly the same thing with your spouse is not possible. Any income you transfer to your spouse which generates any income will be treated as your income only. However, if you are going to be married in some months and you have some big amount of cash, you can gift her right away, as gift given to prospective wife would become hers lawfully!
2. Claim stamp duty and registration fees in 80C
Many people dont know this, but the Stamp duty and the registration fees of the documents for the house can be claimed as deduction under section 80C in the year of purchase of the house. An important point to note here is that you should be in possession of the house if you want to claim these deductions. So in case of under-construction properties, you lose out on claiming this deduction. As per the income tax
The stamp duty, registration fee and other expenses incurred for the purpose of transfer shall also be covered. Payment towards the cost of house property, however, will not include, admission fee or cost of share or initial deposit or the cost of any addition or alteration to, or, renovation or repair of the house property which is carried out after the issue of the completion certificate by competent authority, or after the occupation of the house by the assessee or after it has been let out. Payments towards any expenditure in respect of which the deduction is allowable under the provisions of section 24 of the Income-tax Act will also not be included in payments towards the cost of purchase or construction of a house property.
3. Get deduction for rent even without HRA
All the salaries class people get HRA from their companies, and hence they claim deductions on that. However, what if you are self-employed professional or working for a company who does not provide you HRA benefit? Can you still claim HRA? Yes! But with some caveats.
Under Section 80GG, you can claim deduction of the rent paid even if you don’t get HRA. However not many people are aware of this deduction. If you are not being paid any HRA or don’t have any housing benefit from employer. You can claim least of following 3 things as HRA
a) Rent paid less 10% of total income
b) or Rs 2,000 a month;
c) or 25% of total income.
Note that your spouse or minor child should not own any house with the city limit if you want to claim this benefit , You will have to submit a form called 10-BA that you are paying rent and not receiving HRA.
Bonus tip : If you are staying with your parents, you can pay them rent. If they don’t have
significant income, it would mean you save tax on rent paid and even your parents income does
not cross the tax limits, which is a win-win situation.
4. Declare your losses in tax return to save tax in future
A lot of people do not show their losses in shares, mutual funds, gold ETFs, real-estate in their tax returns. This is a big mistake, as you lose an opportunity to save tax in future years. You can set-off your losses against profits in current year as well as in the future too. For example : Assume you had sold your real-estate property and made a profit of 10 lacs after indexation. You will have to pay a tax of Rs 2 lacs @20%. However suppose in the same year you have also made a loss of Rs 4 lacs in stocks , you can set-off this loss with your 10 lacs profit and just pay tax on Rs 6 lacs , which comes at 1.2 lacs only. That’s a cool 80k in savings!
Also if you have only losses this year and no profits, you can show this loss in your tax returns and carry forward and set-off this loss against any future profits for next 8 yrs. For more details read this article.
5. Buy House with Parent or Siblings as joint-owners
Yes, if you thought only spouse can be co-owner in the real-estate property to claim the tax deductions, you don’t know the whole story. You can have your spouse/parent/siblings as co-owner and all the co-owners can claims the tax deductions of 1 lacs for principal and 1.5 lacs for interest part . So if you take a housing loan with your siblings as co-owner of property and co-Borrower of loan, the loan amount interest and principle paid will be available for tax exemption in ratio of your loan amount.
So if you are still a bachelor or a single who wants to buy a house, consider asking your brother, sister or parents to become the co-owner so that both of you can get tax benefits and reduce your tax-outgo. The only problem in this case is that loan-sanctioning companies are very stringent in giving loans to siblings, as their are higher chances of you parting your ways with them later in case of any family issues, however in case of spouse it happens lesser.
Bonus Tip : The co-owner who falls in the higher tax bracket should hold a higher proportion
of home loan to make sure that the tax benefits are maximised.
6. Use education loan to lower tax for your Children in Future
So what, if you have all the money to pay for your children’s education fees? It would be wise to opt for an education loan in name of your children’s name as you can claim the full interest paid on education loan under section 80E. Note that its only available if you are a parent or a legal guardian . You can’t claim deduction for your spouse education loan
The other thing is that you can take education loan on your children name so that after some years when they pay off their loans, they can claim the deductions themselves. Apart from this, they’d be more responsible and this education loan payment from their pocket will make sure that they don’t spend to much money in wrong places and you can use your money today some where else!
So what, if you have all the money to pay for your children’s education fees? It would be wise to opt for an education loan in name of your children’s name as you can claim the full interest paid on education loan under section 80E. Note that its only available if you are a parent or a legal guardian . You can’t claim deduction for your spouse education loan
The other thing is that you can take education loan on your children name so that after some years when they pay off their loans, they can claim the deductions themselves. Apart from this, they’d be more responsible and this education loan payment from their pocket will make sure that they don’t spend to much money in wrong places and you can use your money today some where else!
7. Take unlimited deductions for your second home loan interest payment
If you have already bought first home where you are living right now and want to buy another house, the good news is that you can claim full interest paid for the EMIs of second house. As per tax laws, you can claim full deductions for the amount paid as interest on loan for second house.
For the first house you can claim up to 1.5 lacs in interest, however for your second house you can claim full amount of interest without any upper limit!
Which of the above tips were new for you ? Can you share any tip which you know but its not covered here ? Please comment .

Heap space setting for Tomcat on Linux

2011-10-11T05:50:00.001-07:00

there are two jvm options for heap size:

-Xms and -Xmx

-Xms - is the minimum or initial size of your heap
-Xmx - is the maximim size

you set these parameters on java command line:

e.g.:

# java -Xmx128m -Xms128m com.mypackage.MyClass

the command above runs your class with java heap set to 128MB

Tomcat has its own startup script(s), which expect java command options to be in JAVA_OPTS environment variable. This is mainly because you dont have direct access to java command line when you run tomcat. So to run Tomcat with 256MB of heap you do something like:

# export JAVA_OPTS="-Xmx256m -Xms256m"
# ./startup.sh

In server environment you should keep -Xms and -Xms the same, unless you have specific reasons why not to allocate all memory from the beginning.

The realistic maximum heap size on 32bit linux is 1900m. You can push it up to 2000m but there is high risk of jvm crash.

On 64mit linux the maximum heap size is almost in all cases more then RAM you ever have.

Medicine for Blood Cancer!!!!

2011-07-31T06:34:00.000-07:00

All,

See the below link from Adyar Cancer Institute:-

http://hoaxalert.blogspot.com/2010/07/imitinef-mercilet-free-blood-cancer.html

The medicine Imitinef is available free for only qualified persons and not for all. It is free for those who have admitted in the hospital for treatment.
'Imitinef Mercilet' is apparently an alternative spelling of the drug Imatinib mesylate which is used in the treatment of some forms of leukemia along with other types of cancer.
Imatinib is available for cancer patients in many different health facilities around the world, not just the Adyar Cancer Institute.
While drugs (including Imatinib), along with other treatments such as radiation can help to slow or even stop the progress of these cancers, there is currently no single drug treatment that can be said to actually cure all such cancers.

Earn upto Rs. 9,000 pm checking Emails. Join now!

2011-07-31T00:29:00.001-07:00

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By logging into your account everyday, they pay you for every unique login in 24 Hours. I get around 0.10 INR everyday by this method.

You can earn money by reading paid mails by which you can earn minimum of 0.10 INR and maximum can't say. I earned Re. 1.

By referring friends, you will get Rs.2 for every friend you invite and Rs.100 for the first 2 referred friends ( i don't know if this promotion is still available or not).

So don't wait so much and don't think so much just

http://www.PaisaLive.com/register.asp?3858412-4351777

Question from Apache

2011-05-17T06:26:00.000-07:00

1. In which folder are Java Applications stored in Apache?
Java applications are not stored in Apache, it can be only
connected to a other Java webapp hosting webserver using the
mod_jk connector

2.Is running apache as a root is a security risk?
No.root process opens port 80, but never listens to it, so
no user will actually enter the site with root rights. If
you kill the root process, you will see the other kids
disappear as well.

3.If you specify both deny from all and allow from all, what will be the default action of Apache?
deny will be taken first.

4.What does htpasswd do?
The htpasswd protects a file with a password

5.What is mod_vhost_alias?
This module creates dynamically configured virtual hosts, by allowing the IP address and/or the Host: header of the HTTP request to be used as part of the pathname to determine what files to serve. This allows for easy use of a huge number of virtual hosts with similar configurations.

6.What is ServerType directive?
It defines whether Apache should spawn itself as a child process (standalone) or keep everything in a single process (inetd). Keeping it inetd conserves resources. This is deprecated, however.

7.How do you set up a virtual host in Apache?
ServerAdmin admin@test.com
DocumentRoot /home/apache/share/htdocs/hostedsites
ServerName www.test.com
ErrorLog /home/apache/logs/error/hostedsites/error_log
TransferLog /home/apache/logs/access/hostedsites/access_log

8.How do you check for the httpd.conf consistency and any errors in it?
apachectl configtest

9.What does apachectl graceful do?
Gracefully restarts the Apache httpd daemon. If the daemon is not running, it is started. This differs from a normal restart in that currently open connections are not aborted. A side effect is that old log files will not be closed immediately. This means that if used in a log rotation script, a substantial delay may be necessary to ensure that the old log files are closed before processing them. This command automatically checks
the configuration files as in configtest before initiating the restart to make sure Apache doesn?t die.
This is equivalent to apachectl -k graceful.

Actually it sends a SIGUSR1 for a restart. The USR1 or graceful signal causes the parent process to advise the children to exit after their current request (or to exit immediately if they’re not serving anything). The parent re-reads its configuration files and re-opens its log files. As each child dies off the parent replaces it with a child from the new generation of the configuration, which begins serving new requests immediately.

10.What is the command to stop Apache?
service httpd stop & apachectl stop

11.On a fresh install, why does Apache have three config files – srm.conf, access.conf and httpd.conf?
The first two are remnants from the NCSA times, and
generally you should be ok if you delete the first two, and
stick with httpd.conf.

12.Hi, When i’m starting startup.bat file of Tomcat server it isn’t started. DOS window appears for a Second only. What should I do?
Your set up might have been not done well. Make sure you have added tomcat root directory path in the CATALINA_HOME environment variable and added the bin path in the path variable

13.What is the difference between Tomcat 4.1 and Tomcat 5.0?
Web server (for development) that supports servlets 2.3 and JSP 1.2 (Tomcat 4) or servlets 2.4 and JSP 2.0 (Tomcat 5).

14.please let me know the configuration or architecture how
tomcat used. give me a layman example The Architecture of Tomcat

Tomcat 4 is a complete rewrite of its ancestors. At the core of this rewrite is the Catalina servlet engine, which acts as the top-level container for all Tomcat instances.

With this rewrite of Tomcat comes an entirely new architecture composed of a grouping of application containers, each with a specific role. The sum of all of these containers makes up an instance of a Catalina engine.

The following code snippet provides an XML representation of the relationships between the different Tomcat containers:

This instance can be broken down into a set of containers including a server, a service, a connector, an engine, a host, and a context. By default, each of these containers is configured using the server.xml file, which we describe
later in more detail.

The Server

The first container element referenced in this snippet is the element. It represents the entire Catalina servlet engine and is used as a top-level element for a single Tomcat instance. The element may contain one or more containers.

The Service

The next container element is the element, which holds a collection of one or more elements that share a single element. N-number of elements may be nested inside a single element.

The Connector

The next type of element is the element, which defines the class that does the actual handling requests and responses to and from a calling client application.

The Engine

The third container element is the element. Each defined can have only one element, and this single component handles all requests received by all of the defined components defined by a parent service.

The Host

The element defines the virtual hosts that are contained in each instance of a Catalina . Each can be a parent to one or more Web applications, with each being represented by a component.

The Context

The element is the most commonly used container in a Tomcat instance. Each element represents an individual Web application that is running within a defined . There is no limit to the number of contexts that can be defined within a .

15.what is tomcat?can we deploy a servelet in tomcat?
Tomcat is a webserver, Which is support 3 -tier archeticture..

Yes we can

in web.xml

16.if i delete my java class files after the compile?but it does not goes to the recycle bin.Now i want to get the java class file
Yes you can

17.what is different between web server and application server?
Web server supports only http protocol
Where as application server supports any type of protocols such as tcp/ip,http etc..

18.what is webserver? why it is used ?
Transaction with HTTP request and HTTP response is called webserver.
Using the internet listening the HTTP request and providing the HTTP response is also called webserver.It gives only html output.It will not process business logic .They can provide Http server.They are static.

19. Can we use Active Server Pages (ASP) with Apache?
Apache Web Server package does not include ASP support.

However, a number of projects provide ASP or ASP-like
functionality for Apache. Some of these are:

Apache::ASP

mod_mono

Chilisoft ASP

20.Why doesn’t Apache include SSL?
SSL (Secure Socket Layer) data transport requires encryption, and many governments have restrictions upon the import, export, and use of encryption technology.

If Apache included SSL in the base package, its distribution would involve all sorts of legal and bureaucratic issues, and it would no longer be freely
available.

Also, some of the technology required to talk to current clients using SSL is patented by RSA Data Security, who restricts its use without a license.

21.Does Apache come with Java support?
The base Apache Web server package does not include support for Java

22.This is very strange.

I am running apache 2.2 (compiled with gcc and all default params) on
AIX 5.2.0.6 – 64 bit kernel.

I edit the httpd.conf file to listen on two different
ports –

Listen 8000
Listen 8001

The server will not start no errors or anything it just accepts the
command but nothing starts.

I can comment out on of the entires and everything starts up just fine
minus the commented out port.

Listen 8000
#Listen 8001

So, my problem is that I cannot get apache to listen on two ports, any
ideas? Has someone else seen this before?

Thanks,

try setting environment flag:
ac_cv_o_nonblock_inherited=no
just before running configure…

and also

apache is a server.we can run each server in unique listen port so we are unable to run same server in two different ports.but u can run on different unique ports. in apache webserver u change that in httpd.conf listen
port to 8080 (default is 80).that listen port belongs to http port for reciving requests and send responces.so please try to understand that which port belongs to which one.

23.Does Apache include any sort of database integration?
Apache is a Web (HTTP) server, not an application server. The base package does not include any such functionality. See the PHP project and the mod_perl project
for examples of modules that allow you to work with databases from within the Apache environment.

24.What is Apache?
Apache is a freely available Web server that is distributed under an “open source” license. Version 2.0 runs on most Unix-based operating systems (such as Linux, Solaris,Digital UNIX, and AIX), on other UNIX/POSIX-derived systems(such as Rhapsody, BeOS, and BS2000/OSD), on AmigaOS, and on Windows 2000. According to the Netcraft (www.netcraft.com)
Web server survey in February, 2001, 60% of all Web sites on the Internet are using Apache (62% including Apache derivatives), making Apache more widely used than all other Web servers combined.

25.Does Apache act as a Proxy server?
Yes, It acts as proxy also by using the mod_proxy module

Red Hat Interview Questions

2011-05-17T06:25:00.000-07:00

1.In which File is Static IP address given so that it becomes Permanent?
/etc/sysconfig/network-scripts/ifcfg-eth0
2.To Check Which Service is running at Present in System what is the Command?
service –status-all
ps –ef
3.How to trace any process background processing?
ps -aux
4.How to build new filesystem ? and what is irig file system?
mke2fs /dev/hda(sda)
mkfs
mk
5.Which command is used to see all the system configuration?
like hardware, HDD, memory etc.
lspci -vv
6.What is the difference between Telnet and SSH?
ssh is a secured shell, where telnet is not a secured
one.when you ssh to trasnfer data between a system, the data
will be send in the encrypted form, where the hacker cannot
encode or decode it. While you telnet,the data send between
the system is alphabetical format(ASCII), where every one
can understand. More over as per network security, telnet
and ftp are prohibited. Always, trust SSL based data transfer.
7.What is the difference between unix and linux…
graphics is the main difference
extra more command are in linux
userfriendly then unix
8.what is mean by raid and what are all raids available even in software and hardware?
Raid Stands for Redundant Array of Independent Disks.It is
a set of Technology standards for Teamingup DiskDrives to
improve Performence and FaultTolerance. Totally there are 6
levels in Raid
0 – stripping
1 – Mirroring
2 – Stripping and Mirroring
3 – Onfficially Not Defined
4 – Striping with Differential Parity
5 – Striping with Distributional Parity
9.why the kernel panic error was appering?
kernel panic acured when linux kernel can not communicat with any hardware or any OS related file
10.What are the main differences between RHEL4 & RHEL5?
Of course RHEL5 security is the main advantage than RHEL4
in RHEL5 it has the updates like XEN, Yum and many
additional packages which supports all the third party softwares
11. How To Hide the FTP Version?
Stop httpd service.
12.what is difference between inetd and xinetd ?
The major difference between inetd and the newer xinetd is that inetd uses a single configuration file, with one line per service, while xinetd uses a configuration directory, with one file per service
13.What is LILO?
LILO stands for Linux boot loader. It will load the MBR, master boot record, into the memory, which tell the system which partition and hard drive to boot.
14.why accounting Software does not support on linux?
Bcoz the accounting software is have .exe file. And linux doesn’t support .exe file. so accounting software does not support on linux.
15.How to give 2 different gateway IP addresses for 2 different interfaces in same system ?
route add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.0.2 dev eth0
route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.0.3 dev eth1
16.How does the boot process[init levels] work on Linux?
1. The system BIOS checks the system and launches the first
stage boot loader on the MBR of the primary hard disk.
2. The Frist stage boot loader loads itself into memory and
launches the second stage boot loader from the /boot/
partition.
3. The second stage boot loader loads the kernel into
memory, which in turn loads any necessary modules and
mounts the root
partition read-only.
4. The kernel transfers control of the boot process to the /
sbin/init program.
5. The /sbin/init program loads all services and user-space
tools, and mounts all partitions
listed in /etc/fstab.
6. The user is presented with a login screen for the
freshly booted Linux system.
17.What is the difference between an argument and an option/switch?
option specifies the command how to run
arguement specifies the command on what to run
18.How to send automated email to a set of people at fixed time ?
Just create a alias of people and create a command file and create a crond entry.
19.What is the minimum number of partitions you need to install Linux?
/
/boot
/swap
20.There are 4 network Interfaces, how can we find which one is Primary ?
When you type the command netstat -nr in your shell, youwill find a line starting with 0.0.0.0. Something like
0.0.0.0 192.168.0.4 0.0.0.0 UG 0 0 0 eth0
This line indicates if the system tries to contact a network outside its local network. It will first contact the router 192.168.0.4 and it does it with the primary interface. Hence in this case its eth0. So you can check this line for the primary interface
21.What is the difference between home directory and working directory?
Home directory is one over which user have complete control and it is its default working directory when its logs in. while the working directory is the users current directory which may or may not be his home directory.
22.How can you see all mounted drives?
we can see all mounted drives
#mount
#df -Th
23.How to check all open ports on linux machine and block unsed ports?
open ports – nmap localhost
block unsed ports -
#nmap -v localhost for tcp
#nmap -sU localhost for udp
24.What are RPM?s, what do they offer?
The full form of RPM is Redhat Package Manager. rpm is a powerful Package Manager, which can be used to build,install, query, verify, update, and erase individual software packages. A package consists of an archive of files and meta-data used to install and erase the archive files.
25.You want to create a compressed backup of the users’ home directories. What utility should you use?
tar -cvzf user.tar.gz /home/user
26.What utility can you use to automate rotation of logs?
logrotate
27.How u use the iptable firewall to restrict ssh,telnet,ftp ?
iptables -A INPUT -s -p tcp –dport -j REJECT/DROP/DENY
28.What file should you examine to determine the defined runlevels for your system?
/etc/inittab
29.What is the name and path of the main system log?
var/log/messages - system log messages can be seen here
/var/log/dmesg - Kernel boot log messages can view

100 Windows XPkeyboard shortcuts

2011-05-17T06:21:00.000-07:00

CTRL+C (Copy)
CTRL+X (Cut)
CTRL+V (Paste)
CTRL+Z (Undo)
DELETE (Delete)
SHIFT+DELETE (Delete the selected item permanently without placing the item in the Recycle Bin)
CTRL while dragging an item (Copy the selected item)
CTRL+SHIFT while dragging an item (Create a shortcut to the selected item)
F2 key (Rename the selected item)
CTRL+RIGHT ARROW (Move the insertion point to the beginning of the next word)
CTRL+LEFT ARROW (Move the insertion point to the beginning of the previous word)
CTRL+DOWN ARROW (Move the insertion point to the beginning of the next paragraph)
CTRL+UP ARROW (Move the insertion point to the beginning of the previous paragraph)
CTRL+SHIFT with any of the arrow keys (Highlight a block of text)
SHIFT with any of the arrow keys (Select more than one item in a window or on the desktop, or select text in a document)
CTRL+A (Select all)
F3 key (Search for a file or a folder)
ALT+ENTER (View the properties for the selected item)
ALT+F4 (Close the active item, or quit the active program)
ALT+ENTER (Display the properties of the selected object)
ALT+SPACEBAR (Open the shortcut menu for the active window)
CTRL+F4 (Close the active document in programs that enable you to have multiple documents open simultaneously)
ALT+TAB (Switch between the open items)
ALT+ESC (Cycle through items in the order that they had been opened)
F6 key (Cycle through the screen elements in a window or on the desktop)
F4 key (Display the Address bar list in My Computer or Windows Explorer)
SHIFT+F10 (Display the shortcut menu for the selected item)
ALT+SPACEBAR (Display the System menu for the active window)
CTRL+ESC (Display the Start menu)
ALT+Underlined letter in a menu name (Display the corresponding menu)
Underlined letter in a command name on an open menu (Perform the corresponding command)
F10 key (Activate the menu bar in the active program)
RIGHT ARROW (Open the next menu to the right, or open a submenu)
LEFT ARROW (Open the next menu to the left, or close a submenu)
F5 key (Update the active window)
BACKSPACE (View the folder one level up in My Computer or Windows Explorer)
ESC (Cancel the current task)
SHIFT when you insert a CD-ROM into the CD-ROM drive (Prevent the CD-ROM from automatically playing)
Dialog Box Keyboard Shortcuts
CTRL+TAB (Move forward through the tabs)
CTRL+SHIFT+TAB (Move backward through the tabs)
TAB (Move forward through the options)
SHIFT+TAB (Move backward through the options)
ALT+Underlined letter (Perform the corresponding command or select the corresponding option)
ENTER (Perform the command for the active option or button)
SPACEBAR (Select or clear the check box if the active option is a check box)
Arrow keys (Select a button if the active option is a group of option buttons)
F1 key (Display Help)
F4 key (Display the items in the active list)
BACKSPACE (Open a folder one level up if a folder is selected in the Save As or Open dialog box)
Micro$oft Natural Keyboard Shortcuts
Windows Logo (Display or hide the Start menu)
Windows Logo+BREAK (Display the System Properties dialog box)
Windows Logo+D (Display the desktop)
Windows Logo+M (Minimize all of the windows)
Windows Logo+SHIFT+M (Restore the minimized windows)
Windows Logo+E (Open My Computer)
Windows Logo+F (Search for a file or a folder)
CTRL+Windows Logo+F (Search for computers)
Windows Logo+F1 (Display Windows Help)
Windows Logo+ L (Lock the keyboard)
Windows Logo+R (Open the Run dialog box)
Windows Logo+U (Open Utility Manager)
Accessibility Keyboard Shortcuts
Right SHIFT for eight seconds (Switch FilterKeys either on or off)
Left ALT+left SHIFT+PRINT SCREEN (Switch High Contrast either on or off)
Left ALT+left SHIFT+NUM LOCK (Switch the MouseKeys either on or off)
SHIFT five times (Switch the StickyKeys either on or off)
NUM LOCK for five seconds (Switch the ToggleKeys either on or off)
Windows Logo +U (Open Utility Manager)
Windows Explorer Keyboard Shortcuts
END (Display the bottom of the active window)
HOME (Display the top of the active window)
NUM LOCK+Asterisk sign (*) (Display all of the subfolders that are under the selected folder)
NUM LOCK+Plus sign (+) (Display the contents of the selected folder)
NUM LOCK+Minus sign (-) (Collapse the selected folder)
LEFT ARROW (Collapse the current selection if it is expanded, or select the parent folder)
RIGHT ARROW (Display the current selection if it is collapsed, or select the first subfolder)
Shortcut Keys for Character Map
After you double-click a character on the grid of characters, you can move through the grid by using the keyboard shortcuts:
RIGHT ARROW (Move to the right or to the beginning of the next line)
LEFT ARROW (Move to the left or to the end of the previous line)
UP ARROW (Move up one row)
DOWN ARROW (Move down one row)
PAGE UP (Move up one screen at a time)
PAGE DOWN (Move down one screen at a time)
HOME (Move to the beginning of the line)
END (Move to the end of the line)
CTRL+HOME (Move to the first character)
CTRL+END (Move to the last character)
SPACEBAR (Switch between Enlarged and Normal mode when a character is selected)
Micro$oft Management Console (MMC) Main Window Keyboard Shortcuts
CTRL+O (Open a saved console)
CTRL+N (Open a new console)
CTRL+S (Save the open console)
CTRL+M (Add or remove a console item)
CTRL+W (Open a new window)
F5 key (Update the content of all console windows)
ALT+SPACEBAR (Display the MMC window menu)
ALT+F4 (Close the console)
ALT+A (Display the Action menu)
ALT+V (Display the View menu)
ALT+F (Display the File menu)
ALT+O (Display the Favorites menu)
MMC Console Window Keyboard Shortcuts
CTRL+P (Print the current page or active pane)
ALT+Minus sign (-) (Display the window menu for the active console window)
SHIFT+F10 (Display the Action shortcut menu for the selected item)
F1 key (Open the Help topic, if any, for the selected item)
F5 key (Update the content of all console windows)
CTRL+F10 (Maximize the active console window)
CTRL+F5 (Restore the active console window)
ALT+ENTER (Display the Properties dialog box, if any, for the selected item)
F2 key (Rename the selected item)
CTRL+F4 (Close the active console window. When a console has only one console window, this shortcut closes the console)

Remote Desktop Connection Navigation
CTRL+ALT+END (Open the m*cro$oft Windows NT Security dialog box)
ALT+PAGE UP (Switch between programs from left to right)
ALT+PAGE DOWN (Switch between programs from right to left)
ALT+INSERT (Cycle through the programs in most recently used order)
ALT+HOME (Display the Start menu)
CTRL+ALT+BREAK (Switch the client computer between a window and a full screen)
ALT+DELETE (Display the Windows menu)
CTRL+ALT+Minus sign (-) (Place a snapshot of the active window in the client on the Terminal server clipboard and provide the same functionality as pressing PRINT SCREEN on a local computer.)
CTRL+ALT+Plus sign (+) (Place a snapshot of the entire client window area on the Terminal server clipboard and provide the same functionality as pressing ALT+PRINT SCREEN on a local computer.)
Micro$oft Internet Explorer Navigation
CTRL+B (Open the Organize Favorites dialog box)
CTRL+E (Open the Search bar)
CTRL+F (Start the Find utility)
CTRL+H (Open the History bar)
CTRL+I (Open the Favorites bar)
CTRL+L (Open the Open dialog box)
CTRL+N (Start another instance of the browser with the same Web address)
CTRL+O (Open the Open dialog box, the same as CTRL+L)
CTRL+P (Open the Print dialog box)
CTRL+R (Update the current Web page)
CTRL+W (Close the current window