Static IP in REDHAT Linux accessing by Oracle Virtual Box

I installed REDHAT linux  on oracle virtual box and now because i had to take a trip, i can only ssh into my server and i have to change my ip adress, Originally when i installed the os, i set it to DHCP, but now i want to change it to a static ip. so if you are in the same situation as i am, maybe you can learn from this on how you can change your ip address remotely..

these are the steps i took to make it happen

1. login as root

2. get your current IP address with this command:

ifconfig

The OUTPUT will look someting like this:

[root@host ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:D0:BC:08:09:BC
inet addr:70.238.17.69 Bcast:255.255.255.255 Mask:255.255.255.248
inet6 addr: fe80::2d0:b7ff:fe08:9bb/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:7174 errors:0 dropped:0 overruns:0 frame:0
TX packets:2305 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:5339910 (5.0 MiB) TX bytes:170109 (166.1 KiB)

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:34 errors:0 dropped:0 overruns:0 frame:0
TX packets:34 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:4275 (4.1 KiB) TX bytes:4275 (4.1 KiB)

OR you can also get the ip from the network configuration file wit this command:
COMMAND to show configuration:

cat /etc/sysconfig/network-scripts/ifcfg-eth0

THe OUTPUT will look like this (i have it set to DHCP)

DEVICE=eth0
BOOTPROTO=dhcp
HWADDR=00:D0:B7:08:09:BB
ONBOOT=yes

Change to static IP as follows :

Just comment the existing ip configuration.

OUTPUT for static IP (example)

#
# File: ifcfg-eth0
#
DEVICE=eth0
IPADDR=192.168.1.100
NETMASK=255.255.255.0
BOOTPROTO=static
ONBOOT=yes
#
# The following settings are optional
#
BROADCAST=192.168.1.255
NETWORK=192.168.1.0

4. Disable Firewall on RHEL / CentOS / RedHat Linux

Next enter the following three commands to disable firewall.

# service iptables save

# service iptables stop

# chkconfig iptables off

If you are using IPv6 firewall, enter:

# service ip6tables save

# service ip6tables stop

# chkconfig ip6tables off

5.  Now save your changes and reboot your server.

***********************

6. The network type should be bridged on Virtual Box. 

Cheers

Rajani

Database Normalization

In relational database design, we not only want to create a structure that stores all of the data, but we also want to do it in a way that minimize potential errors when we work with the data. The default language for accessing data from a relational database is SQL. In particular, SQL can be used to manipulate data in the following ways: insert new data, delete unwanted data, and update existing data. Similarly, in an un-normalized design, there are 3 problems that can occur when we work with the data:

INSERT ANOMALY: This refers to the situation when it is impossible to insert certain types of data into the database.

DELETE ANOMALY: The deletion of data leads to unintended loss of additional data, data that we had wished to preserve.

UPDATE ANOMALY: This refers to the situation where updating the value of a column leads to database inconsistencies (i.e., different rows on the table have different values).

To address the 3 problems above, we go through the process of normalization. When we go through the normalization process, we increase the number of tables in the database, while decreasing the amount of data stored in each table. There are several different levels of database normalization:

1st Normal Form (1NF)
2nd Normal Form (2NF)
3rd Normal Form (3NF)
Bryce-Codd Normal Form (BCNF)
4th Normal Form (4NF)
5th Normal Form (5NF)
The opposite of normalization is denormalization, where we want to combine multiple tables together into a larger table. Denormalization is most frequently associated with designing the fact table in a data warehouse.


1st Normal Form Definition

A database is in first normal form if it satisfies the following conditions:

• Contains only atomic values
• There are no repeating groups

An atomic value is a value that cannot be divided. For example, in the table shown below, the values in the [Color] column in the first row can be divided into "red" and "green", hence [TABLE_PRODUCT] is not in 1NF.

A repeating group means that a table contains two or more columns that are closely related. For example, a table that records data on a book and its author(s) with the following columns: [Book ID], [Author 1], [Author 2], [Author 3] is not in 1NF because [Author 1], [Author 2], and [Author 3] are all repeating the same attribute.

1st Normal Form Example

How do we bring an unnormalized table into first normal form? Consider the following example:

This table is not in first normal form because the [Color] column can contain multiple values. For example, the first row includes values "red" and "green."

To bring this table to first normal form, we split the table into two tables and now we have the resulting tables:

Now first normal form is satisfied, as the columns on each table all hold just one value.

2nd Normal Form Definition

A database is in second normal form if it satisfies the following conditions:

• It is in first normal form
• All non-key attributes are fully functional dependent on the primary key

In a table, if attribute B is functionally dependent on A, but is not functionally dependent on a proper subset of A, then B is considered fully functional dependent on A. Hence, in a 2NF table, all non-key attributes cannot be dependent on a subset of the primary key. Note that if the primary key is not a composite key, all non-key attributes are always fully functional dependent on the primary key. A table that is in 1st normal form and contains only a single key as the primary key is automatically in 2nd normal form.

2nd Normal Form Example

Consider the following example:

This table has a composite primary key [Customer ID, Store ID]. The non-key attribute is [Purchase Location]. In this case, [Purchase Location] only depends on [Store ID], which is only part of the primary key. Therefore, this table does not satisfy second normal form.

To bring this table to second normal form, we break the table into two tables, and now we have the following:

What we have done is to remove the partial functional dependency that we initially had. Now, in the table [TABLE_STORE], the column [Purchase Location] is fully dependent on the primary key of that table, which is [Store ID].

3rd Normal Form Definition

A database is in third normal form if it satisfies the following conditions:

• It is in second normal form
• There is no transitive functional dependency

By transitive functional dependency, we mean we have the following relationships in the table: A is functionally dependent on B, and B is functionally dependent on C. In this case, C is transitively dependent on A via B.

3rd Normal Form Example

Consider the following example:

In the table able, [Book ID] determines [Genre ID], and [Genre ID] determines [Genre Type]. Therefore, [Book ID] determines [Genre Type] via [Genre ID] and we have transitive functional dependency, and this structure does not satisfy third normal form.

To bring this table to third normal form, we split the table into two as follows:

Now all non-key attributes are fully functional dependent only on the primary key. In [TABLE_BOOK], both [Genre ID] and [Price] are only dependent on [Book ID]. In [TABLE_GENRE], [Genre Type] is only dependent on [Genre ID].