How to break root pasword of linus with snapshot? Or,
How to set new password of root without log into the root user?
Step 01 : Press any button or space bar in the window . And Press "a" to modify.
Step 3: After that this window will come . after rhgb quiet >> write "1" . it will give you access to single user interface.
Step 3 : After that when this window come . Write "passwd" and it will prompt to set the password . Now set the new password as your wish ! and reboot ! And enjoy :- )
(1) Configure Host Name
# vim /etc/sysconfig/network
(2) Configure IP Address, Gateway and DNS.
Validate these profiles:
a) Check gateway: # vim / etc / sysconfig / network
b) Check Host Name: # vim /etc/hosts
c) Check DNS: # vim /etc/resolv.conf
d) Check Gateway: # vim /etc/sysconfig/network-scripts/ifcfg-eth0
Question 1 In accordance with the following requirements to deploy ssh login service: (1) Make example.com which can remote login your systems. (2) Where, users of remote.test can not use ssh login to your machine.
Transmission Control Protocol(TCP) and Internet protocol(IP):-
1. IP :- they control Routing of information to different devices, servers , etc. deals with default address , gateway, DNS , It is routable protocol.
Internet protocol is used for
transmission of data over the internet. IP uses IP addresses to identity each
machine uniquely. Message is sent using small packets. The packet contains both
the sender and receivers address. IP does not guarantee the delivery in the
same order as sent. This is because the packets are sent via different routes.
It is a connectionless communication protocol at the third level (network) of
the OSI model.
2. TCP :- It actually means when Two computer connected it is the process the determined how this computer may talked to each other. It is OSI layer 4 (Transport Layer)
Transmission control Protocol is used to establish communication between
nodes or networks and exchange data packets. It guarantees delivery of data
packets in the order they were sent. Hence it is most commonly used in all
applications that require guaranteed delivery of data. It can handle both
timeouts (if packets were delayed) and retransmission (if packets were lost).
The stream of data is transmitted in segments. The segment header is 32 bit. it
is a connectionless communication protocol at the third level (network) of the
OSI model.
How these computer talked to each other? When they are connected what they do they started to send packet to each other. So, They Exchange packet with each other and they double their sending of packets from 1,2,4,8,16 ... but every time they are facing interruption then they again staring they are from starting point means from 1 packets then 2 , 4, 8 . 16 ... And this process is called windowing.
How TCP/IP works:-
Components : -
IP:- Every computer need IP address to communicate with each other. example:- 10.0.0.1,192.168.2.1 etc
Subnet mask :- Next you need Subnet mask and which helps to segment a network logically . but remember router connects different subnets.
Default Gateway :- Then comes Default Gateway is the router for subnetwork.
DNS :- Lastly comes DNS server which is used to mapped domain name with the ip address.
·Explain the classes of IP
address
IP addresses are organized into classes. For
convenience of humans, IP addresses are expressed in the decimal format. Every
number in each class is represented as binary to computers.
The four numbers in an IP address are known
as ‘octets’. Each of them has eight bit positions. The octets are divided into
two sections: Net and Host. The first octet represents Net for identifying the
network and the Host contains the last octet. There are five IP classes.
Class A: The
class A is used for very large networks. There are 1 to 126 are part of this
class. That means there are 126 Class A networks. Class A networks accounts for
half of the total available IP addresses.
Class B: It
is used for medium size networks. The IP address with a first octet from 128 to
191 is part of this class. Class B networks have a first bit value of 1 and a
second bit value of 0 in the first octet.
Class C: Class
C is used for small to middle size networks. IP address with a first octet
starts from 192-223. Class C networks have a first bit value of 1, second bit
value of 1 and a third bit value of 0 in the first octet.
Class D: It
has first, second and third bit value as 1 and the fourth bit as 0. The other
28 bits are used for identifying the group of computers which is intended for
multicast messages.
Class E: Class
E is used for identification purpose. The four bits value is 1. The other 28
bits are used for identifying the group of computers which is intended for
multicast messages.
·Define Subnetting:-
A subnet describes a set of networked
computers which have common IP address routing prefix.
Breaking the networking into smaller and
more efficient subnets is known as subnets. Subnetting prevents Ethernet packet
collision which has excessive rates in a large network. Routers are used to
manage the traffic and constitute borders among subnets.
Subnetting is
dividing a network into several subnets.
This is usually done for the following purposes:
Reducing network traffic by decreasing the number of broadcasts
Exceeding the limitations in a local area network
Enabling people to connect to the network remotely without
opening the entire network
DHCP:- Dynamic Host Configuration Protocol :-
·Dynamic Host Configuration Protocol is used
assigning IP addresses to computers in a network. The IP addresses are assigned
dynamically. Certainly, using DHCP, the computer will have a different IP
address every time it is connected to the network. In some cases the IP address
may change even when the computer is in network. This means that DHCP leases
out the IP address to the computer for some time. Clear advantage of DHCP is
that the software can be used to manage IP address rather than the
administrator.
DHCP vs Static IP:-
With static IP addressing, addresses are assigned manually, and have to be provisioned carefully so that each device has its own address—with no overlap. When you connect a new device, you would have to select the "manual" configuration option and enter in the IP address, the subnet mask, the default gateway and the DNS server(s). If you understood any of what I just said, you probably have the skills and knowledge necessary to manage static IP addresses on a home network. If it was basically gibberish, you’d probably be more comfortable with DHCP.
DHCP takes all of the manual work out of IP addressing. Generally, the device that's at the "top" of your home network—whether it's a standalone firewall or a router/gateway device or your Control4 home controller—will provide DHCP by default as a service on the network. When DHCP is enabled, a new device connected to the network asks the DHCP server for an address, and the server assigns one from its pool of unused locations. The server itself tracks which addresses are used and which addresses are available, and keeps a record of which addresses have been assigned to the various devices. This ensures that addresses don't conflict with each other. However, it also means that, if a device goes offline, when it reconnects it may not have the same IP address it had before.
What is Network address translation (NAT)
It enables us to reuse IP address. For these every computer or device did not have to use unique ip address.
Network Address Translation translates and IP address used in a network to another IP address known within another network. A NAT table is maintained for global to local and local to mapping of IP’s. NAT can be statically defined or dynamically translate from a pool of addresses. The NAT router is responsible for translating traffic coming and leaving the network. NAT prevents malicious activity initiated by outside hosts from reaching local hosts by being dependent on a machine on the local network to initiate any connection to hosts on the other side of the router.
It is basically Short for Network Address Translation, an Internet standard that enables a local-area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT box located where the LAN meets the Internet makes all necessary IP address translations.
NAT serves three main purposes:
Provides a type of firewall by hiding internal IP addresses
Enables a company to use more internal IP addresses. Since they're used internally only, there's no possibility of conflict with IP addresses used by other companies and organizations.
Allows a company to combine multiple ISDN connections into a single Internet connection.
I found a very useful video , where it explained it very easily .
ARP : Address Resolution Protocol is utilized for mapping IP network address to the hardware address that uses data link protocol.
So,IP address of destination to physical address conversion is done by
ARP, by broadcasting in LAN.
RARP : Reverse Address Resolution Protocol is a protocol using which a physical machine in a LAN could request to find its IP address from ARP table or cache from a gateway server.
And , Physical address of source to IP address conversion is done by
RARP.
ARP associates 32 bit IP address with 48 bit physical address.Allowing a host to discover its internet address after knowing only its physical address is done by RARP.
Use this information to better understand explicit proxy mode on your Gateway appliances.In explicit proxy mode, some network devices must be set up explicitly to send traffic to the device.The device then works as a proxy or relay, processing traffic on behalf of the devices.
Explicit proxy mode is best suited to networks where client devices connect to the device through a single upstream and downstream device.
Here , In this figure firewall and Gateway appliance are connect to a switch.
Basically in this layer information gets from your computer is converted to digital signal ; information taken from strings and convert it to binary and transfer it into the lan. Basically you are transmitting 1 bit or multiple bit at a time. that is what physical layer is responsible for . 2. Data Link Layer :
This is where NIC card just switch to NIC card(Just end to end)
Frame error checking
Responsible for Information you are trying to send is going into correct order.
Frame acknowledgement
Here , CSMA/CD - Carrier Sense Multiple Access / Collision Detection means if it detects collision they basically listen to the line for certain amount of time and when they are free they start transmission again .
3. Network Layer : -
Logical to physical
Traffic control
4.Transport Layer : -
This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer.
- Layer 4 Transport examples include SPX, TCP, UDP.
5. Session Layer :-
This layer establishes, manages and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.
This layer provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa. The presentation layer works to transform data into the form that the application layer can accept. This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems. It is sometimes called the syntax layer.
This layer supports application and end-user processes. Communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. Everything at this layer is application-specific. This layer provides application services for file transfers, e-mail, and other network software services. Telnet and FTP are applications that exist entirely in the application level. Tiered application architectures are part of this layer.
