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294 - mod_rewrite mod_alias

1. mod_rewrite

This module uses a rule-based rewriting engine (based on a regular-expression parser) to rewrite requested URLs on the fly. It supports an unlimited number of rules
and an unlimited number of attached rule conditions for each rule, to provide a really flexible and powerful URL manipulation mechanism.
The URL manipulations can depend on various tests, of server variables, environment variables, HTTP headers, or time stamps.
Even external database lookups in various formats can be used to achieve highly granular URL matching.

293 - MX records

MX stands for Mail Exchange Records. MX records are used in DNS records(or Zone files) to specify how email should be routed.

You can check the following command to look at MX information.

[root@localhost]# nslookup
> set q=mx
> google.com

1. Multiple mail servers

292 - SFDC login parameters

SFDC accepts the parameters added after login URL in order to login directly without entering credential. This is a kind of standard functionality.

https://login.salesforce.com?un=<user name>&pw=<password>



291 - SELinux

SELinux is a security enhancement to Linux which allows users and administrators more control over access control.

Access can be constrained on such variables as which users and applications can access which resources. These resources may take the form of files. Standard Linux access controls, such as file modes (-rwxr-xr-x) are modifiable by the user and the applications which the user runs. Conversely, SELinux access controls are determined by a policy loaded on the system which may not be changed by careless users or misbehaving applications.

290 - thunderbird 5.7.1 relay access denied

After create a new account in thunderbird, you got the following error when sending an e-mail.

 * thunderbird 5.7.1 relay access denied

1. Check the configuration on thunderbird first

o to Tools > Account Settings > [account name] > Server Settings > Advanced > Smtp and verify the correct SMTP server
is selected there. If you see "Relay access denied" or "Relaying denied" errors, be sure to verify this setting.

289 - PHP Header() Function

Redirecting URLs in PHP centers around the PHP Header() function.

For example :
Suppose you want acheter viagra to redirect to this URL http://www.somewebsite.com/target.php.
In the originating PHP page, you will simply call this script in like index.php:


288 - How to break a file system

When you are testing on the recovery and so on, sometimes you may want to break a file system on purpose.

dd if=/dev/zero of=/dev/your_partition bs=512 count=512

Before the above command, make sure whether you can or not.


287 - Oracle Advanced Compression

Advanced Compression provides storage reduction through compression of all data types. It also provides performance improvements in several cases
as compressed blocks result in more data being moved per I/O. It further improves memory efficiency as Oracle Database keeps data compressed in memory.
All these benefits cascade through all the environments such as staging, QA, development, standby, backup, etc., magnifying the benefits several times.

286 - How to know Oracle Version and Patches

Version information is stored in a table called v$version. In this table you can find version information on Oracle, PL/SQL, etc.
To retrieve the version information for Oracle, you execute the following
SQL statement:

SQL> select * from v$version;

285 - Resizing Temporary Tablespace

If you try to drop the temp tablespace, you get the error message as the following.

drop tablespace temp
ERROR at line 1:
ORA-12906: cannot drop default temporary tablespace


1. Create a second temp acheter viagra tablespace.


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by Dr. Radut