Apache-PHP User Authentication

http://www.weberdev.com/ViewArticle/User-Authentication-With-Apache-and-PHP

OFC standards

You might have some confusion about the OFC cable standards, like LC, SC etc. The following link will help you to understand all these standards

http://www.thefoa.org/tech/connID.htm
http://en.wikipedia.org/wiki/Optical_fiber_connector

Redirect Using Iptables

To redirect port 80 to 8080 use:

iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 8080

HowTo get a small sample dataset from a mysql database using mysqldump

Here is a quick tip that will show how you can get a small sample dataset from a mysql database using mysqldump. We frequently need to get a small snapshot from a very big production database to import it into a development or staging database that will not need all the original data; let’s say we need 1,000,000 records from all the tables in the database; we will just use the option –where=”true LIMIT X”, with X the number of records we want mysqldump to stop after.

Simply we will run something like (add whatever other options you need to mysqldump):

 mysqldump --opt --where="true LIMIT 1000000" mydb > mydb1M.sql

and this will get 1M records from each of the tables in the database. If you want this for a single table you would use something like this:

 mysqldump --opt --where="true LIMIT 1000000" mydb mytable > mydb_mytable_1M.sql

To restore this, you would use the same as on a regular dump:

 mysql -p mydb_stage < mydb1M.sql

This will give you a small number of records that you can use for development, testing, etc. whatever you would need.

To find all the files of a particular size.

Let’s assume you are searching for all the files of exactly 6579 bytes size inside the home directory. You will just have to run something like:

 find /home/ -type f -size 6579c -exec ls {} \;

As units you can use:

   * b - for 512-byte blocks (this is the default if no suffix is used)
  * c - for bytes
  * w - for two-byte words
  * k - for Kilobytes (units of 1024 bytes)
  * M - for Megabytes (units of 1048576 bytes)
  * G - for Gigabytes (units of 1073741824 bytes)

You can search for exact file size, or just for bigger (+) or smaller (-) files. For example all bigger than 512k files would be found with something like:

 find /home/ -type f -size +512k -exec ls -lh {} \;

I have added here -lh to the ls output so it will actually show the files with their sizes in a nice human readable format. Similar for smaller files you would use -size -512k.

Change password in single command

echo redhat | passwd --stdin test

This will set the password redhat for user test.

Type Casting column type in Postgres

Consider you have a filled up table in postgres, and one of the column is defined as 'character varying'. Now, if you want to change the column type to 'integer' then the normal alter command will not work.

If you will do this :

alter table tablename alter columnname type integer

you will get this error:

ERROR: column "column_name" cannot be cast to type "pg_catalog.int4"

So, you need to do this:

alter TABLE tablename alter column columnname type integer using columnname::integer;