Powerful VI Editor

The vi editor (short for visual editor) is a screen editor which is available on almost all Unix systems. Once you have learned vi, you will find that it is a fast and powerful editor. vi has no menus but instead uses combinations of keystrokes in order to accomplish commands.

Here are some powerful commands which helps to use vi editor in daily basis:

Note : Using "+" here to indicate that we have to press both the buttons to perform action.

1. Cursor Navigation

j --  next line

k -- previous line

h -- left

l -- right

shift + g -- bottom of document

g + g -- top of document

2. Fast Search

/ -- Search Term

n -- next

N -- previous

3. Command Mode 

: -- enter command mode

:w -- write

:q -- quit  

:e -- open

Esc -- escape command mode

4. From normal to Edit mode

i -- Insert at current position

I -- insert at start of line

A -- append to end of line

o -- Insert line below

O -- Insert line above

5. Clipboard

d+w -- delete word

d+d -- delete line

p -- put after cursor

P -- put before cursor

y+w -- copy word

y+y -- copy line

What happens when you type google.com

Step 1: Request a record

You begin by asking your computer to resolve a hostname, such as visiting 'http://www.google.com' in a web browser. The first place your computer looks is its local DNS cache, which stores DNS information that the computer has recently retrieved.

Step 2: Ask the Recursive DNS servers
If the records are not stored locally, your computer queries (or contacts) your ISP's recursive DNS servers. These machines perform the legwork of DNS queries on behalf of their customers. The recursive DNS servers have their own caches, which they check before continuing with the query.

Step 3: Ask the Root DNS servers
If the recursive DNS servers do not have the record cached, they contact the root nameservers. These thirteen nameservers contain pointers for all of the Top-Level Domains (TLDs), such as '.com', '.net' and '.org'. If you are looking for 'www.google.com.', the root nameservers look at the TLD for the domain - 'www.google.com'- and direct the query to the TLD DNS nameservers responsible for all '.com' pointers.

Step 4: Ask the TLD DNS servers
The TLD DNS servers do not store the DNS records for individual domains; instead, they keep track of the authoritative nameservers for all the domains within their TLD. The TLD DNS servers look at the next part of the query from right to left - 'www.google.com' - then direct the query to the authoritative nameservers for 'google.com'.

Step 5: Ask the Authoritative DNS servers
Authoritative nameservers contain all of the DNS records for a given domain, such as host records (which store IP addresses), MX records (which identify nameservers for a domain), and so on. Since you are looking for the IP address of 'www.google.com', the recursive server queries the authoritative nameservers and asks for the host record for 'www.google.com'.

Step 6: Retrieving the record
The recursive DNS server receives the host record for 'www.google.com' from the authoritative nameservers, and stores the record in its local cache. If anyone else requests the host record for 'www.google.com', the recursive servers will already have the answer, and will not need to go through the lookup process again until the record expires from cache.

Step 7: The Answer!
Finally, the recursive server gives the host record back to your computer. Your computer stores the record in its cache, reads the IP address from the record, then passes this information to the web browser. Your browser then opens a connection to the IP address '72.14.207.99' on port 80 (for HTTP), and our webserver passes the web page to your browser, which displays Google.