How to Configure YUM repository in RHEL 5

Installing packages and configuring Servers we need to configure the YellowDog Update Manager (YUM)
First,

1 If its local repository then
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Install Package createrepo ( this pacakge is present in RHEL 5 dvd in Server folder)

RPM -ivh createrepo

createrepo -v /var/ftp/pub/Server

/var/ftp/pub/Server => this is the directory where local copy of RPM packages are there

Edit the Server.repo file
# vi Server.repo
[Server]
name= redhat
baseurl=file:///var/ftp/pub/Server
[enable=1]
[gpgcheck=0]
Save the file and quit
Then,
#yum clean all
#yum update
Now you can install packages
#yum install package-name



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2 If repository is present in server
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#cd /etc/yum.repos.d
#ls
Then it will list the files. There is a file with name rhel-debuginfo.repo. Copy this file to a temp file with name Sever.repo. The starting letter of Server should be Capital.
Second step is given below

#cp rhel-debuginfo.repo Server.repo
The Third and final steps
Edit the Server.repo file
# vi Server.repo
[Server]
[name= redhat]
[baseurl=ftp://192.168.0.254/pub/Server] ( eg: IP address : 192.168.0.254 (the server IP)
[enable=1]
[gpgcheck=0]
Save the file and quit
Then,
#yum clean all
#yum update
Now you can install packages
#yum install package-name

Configuring YUM behind the HTTP proxy

Under Normal Conditions yum dont work if you are suing internet behind proxy


So in yum.conf add
#The proxy server or IP address:port number


proxy=http://proxy.server.com:8080


Below one if you use ( username/password)


proxy_username=userid
proxy_password=password









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Configure Nagios from scratch

Mount windows partition in linux

First find out partition detail,

#fdisk -l

#mkdir /win

#mount -t msdos /dev/sda1 /win .....(If partition is FAT32)

-or-

#mount -t ntfs /dev/sda1 /win .....(If partition is NTFS)

#cd /win

Note: If your are using RHEL 3,4,5 then NTFS mounting will not be Supported. For that you need to complile a new kernel.

What is SGA

The SGA is a chunk of memory that is allocated by an Oracle Instance during the nomount stage and is shared among Oracle processes, hence the name. It contains all sorts of information about the instance and the database that is needed to operate.

The SGA consists of the following four (five if MTS) parts:

* Fixed Portion
* Variable Portion
* Shared pool
* java pool

Fixed portion
The size of the fixed portion is constant for a release and a plattform of Oracle, that is, it cannot be changed through any means such as altering the initialization parameters

Variable portion
The variable portion is called variable because its size (measured in bytes) can be changed.The variable portion consists of:

* large pool which provides working space for rman (although rman will also work without large pool).
* Shared pool used for objects that are shared among all users.

The shared pool can further be subdivied into:
o Control structures
o Character sets
o Dictionary cache
The dictionary cache stores parts fo the data dictionary because Oracle has to query the data dictionary very often as it is fundamental to the functioning of Oracle.
o Library cache
The library cache is further divided into
+ Shared SQL Area,
+ PL/SQL Procedures and
+ Control Structures (Latches and Locks).

The size of the Shared Pool is essentially governed by the initialization parameter shared_pool_ size (although shared_pool_ size is usually smaller than the size of the shared pool, see here) and db_block_buffers (which plays a role for this size because the database buffer cache must be administered. )

The size for the variable portion is roughly equal to the result of the following statement:

select sum(bytes) from
v$sgastat where
pool in ('shared pool', 'java pool', 'large pool');

Redo log buffer
Redo Buffers is roughly equal to the parameter log_buffer

Database buffer cache
It's size is equal to db_block_size * db_block_buffers.

db_block_buffers is deprecated as of 9i, so if the init parameter db_cache_size) is set, the buffer cache's size will be set according to this value.
UGA
If the instance is running in MTS mode, there'se also a UGA: user global area

You can use v$sga to show the amount of these sizes or alternatively use SHOW SGA in sql*plus.

The following initialization parameters affect the size of the SGA:

* db_block_buffers,
* db_block_size,
* db_cache_size,
* db_keep_cache_ size,
* db_recycle_cache_ size,
* java_pool_size.
* large_pool_size,
* log_buffer,
* shared_pool_ size,
* streams_pool_ size,

The amount of SGA that a user can use can be limitted through profiles. Use the private_sga option in the create profile statement.

Dynamic SGA allows to change the size of the buffer cache, the large pool, the shared pool and the process private memory on the fly, that is without shutting down the instance.

The x$ tables are an sql interface to the SGA and allow to peek into the SGA.Notably, x$ksmmem seems to allow to address every byte in the SGA.

various Admin requirements

Linux
/Solaris/AIX/HPUX/Redhat (Expertise in at least two)


Remote support, KVM, DRAC, ALOM, HMC


Perl/shell scripting(MUST)


LVM/Sun Disk Suite


Network services, NFS, NIS, DNS, Samba.


OpenSource software compilation and installation (gcc, cc)


Knowledge of RAID (0,1,1+0,3,5)


OS installation, kernel configuration


Web servers, apache, iPlanet, tomcat


Monitoring tools, Nagios, Netsaint, OVO, BMC patrol, MRTG, Remedy


Troubleshooting and performance tuning.


Veritas products - File System, Clustering, Volume Manager


OpenPKG / RPM, Sun Packages


Storage knowledge, EMC, HP-EVA, IBM-ESS


Virtualization, Vmware, Xen


Role: Configuration Management-unix and linux admin exp

?The individual should have sound Unix Background, with at least 2years of Administration Skills in Solaris 5.8 and above and Redhat Linux 4 and above.
?The individual should have handson admin experience of at least 4 years in ClearCase ver 6 and above, ClearCase MultiSite
?The individual must be skilled in DesignSync and should have at least 1years hands-on experience with DesignSync
?The individual should posses sufficient knowledgeable of Windows environment to be able to different windows related and Application related issues
?The individual should have knowledgeable in Defect and Requirement Management tools like ClearQuest, RequisitePro
?The individual must exhibit very good programming skills with Perl

Good To Have Skills:
?Knowledge / hands-on with BuildForge, Klockwork, Sourceforge, GIT will be an added advantage

Difference between a database and an instance

The terms instance and database are closely related, but not the same thing.

The database is the set of files where application data (the reason for a database) and meta data is stored.

An instance is the software (and memory) that Oracle uses to manipulate the data in the database. In order for the instance to be able to manipulate that data, the instance must open the database. A database can be opened (or mounted) by more than one instance, however, an instance can open at most one database.

What is a instance

Database programs, with few exceptions, need to utilize both the computer's memory and permanent storage space such as the hard drive to operate. The drives provide both long-term storage and the necessary room for millions of records and gigabytes worth of information.

However, accessing information from disks is much slower than retrieving the same information from memory. Therefore, database engines use memory to cache information, which speeds its retrieval.
The complexity of how the information is stored and where it is retrieved from is hidden from the casual user who queries the database. But if you plan on administering Oracle, you need to become familiar with how Oracle handles both resources.

An instance is the (executed) Oracle software (Oracle processes) and the memory they use (SGA). It is the instance that manipulates the data stored in the database.

It acts as a bridge between the database and the filesystem

Oracle Architecture simplified

Oracle = Instance + Database File

1A) Instance [ SGA + Background Services]
2A) database file [ control file, datafile , redolog file]

SGA
1)Share pool [ library cache , data dictonary cache]
2)database buffer cache
3)Redolog buffer

Background servies
1) Pmon
2) Smon
3) DBWR
4) LGWR
5) CKPT