Interview Questions.

Question 1. What Is Ssh Protocol?

Answer :

SSH, or comfy shell, is a cozy protocol and the most not unusual way of correctly administering faraway servers. Because it encrypt records at the same time as transferring from one host to some other host at some point of network.

Question 2. What Is The Default Port & Configuration File Of Ssh Server ?

Answer :

22 is default port  for ssh and  ‘/and so on/ssh/sshd_config’ is the configuration record.

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Question 3. How To Change The Default Ssh Port In Linux ?

Answer :

To exchange the port , first edit the record ‘ /and many others/ssh/sshd_config ‘ , exchange the fee of parameter ‘ port 22 ‘, now restart the ssh carrier.

Question four. What Is The Configuration File Of Ssh Client ?

Answer :

‘ /etc/ssh/ssh_config ‘ is configuration report for ssh client.

Question 5. What Is Ssh Port Forwarding?

Answer :

SSH Port Forwarding, every now and then referred to as SSH Tunneling, which allows you to set up a secure SSH session after which tunnel arbitrary TCP connections through it. Tunnels can be created at any time, with almost no effort and no programming.

Syntax : ssh -L localport:host:hostport user@ssh_server -N

wherein:

-L – port forwarding parameters

localport – nearby port (chose a port that isn't in use via different carrier)

host – server that has the port (hostport) which you need to ahead

hostport – far off port

-N – do now not execute a far flung command, (you'll not have the shell, see below)

consumer – person which have ssh access to the ssh server (laptop)

ssh_server – the ssh server with a view to be used for forwarding/tunneling

Without the -N alternative you'll have now not simplest the forwarding port however additionally the faraway shell.

Question 6. How To Disable The Root Login In Linux Server ?

Answer :

Open the report ‘ /and many others/ssh/sshd_config ‘ and change the parameter ‘PermitRootLogin sure’ to ‘PermitRootLogin no’ & restart the ssh provider.

Question 7. How To Allow Only Specific Users To Ssh Your Linux Server ?

Answer :

Open the record ‘/and so on/ssh/sshd_config’ and upload the parameter ‘AllowUsers user1 user2′ & then restart the ssh server.

Question 8. What Is The Difference Between Ssh & Telnet ?

Answer :

In ssh communication between purchaser & server is encrypted but in telnet communication between the purchaser & server is in undeniable textual content . We can also say SSH makes use of a public key for authentication whilst Telnet does not use any authentication.SSH provides a piece greater overhead to the bandwidth as compared to Telnet.Default port of ssh is 22 and for telnet 23.

Question nine. What Is Use Of Sshpass Command In Linux ?

Answer :

sshpass is a command which allows us to automatically deliver password to the command activate so that automatic scripts can be run as desired through users. Sshpass materials password to ssh activate the use of a devoted tty , fooling ssh to trust that a interactive user is presenting password.

Question 10. What Is The Use Of Scp Command ?

Answer :

SCP stands for Secure Copy ,it copies documents among hosts over a  network.  It makes use of ssh for facts transfer &  makes use of the equal authentication and gives the identical protection as ssh. Unlike rcp, scp will ask for passwords or passphrases if they're wished for authentication.

Question 11. What Is The Use Of Blowfish Options In Scp Command ?

Answer :

Using blowfish alternatives in scp command , we will boom the speed, via default scp uses the Triple-DES cipher to encrypt the facts being copied.

Example : scp -c blowfish /domestic/itstuff.Txt root@mail.Amitmaheshwari.In:/opt/

Question 12. How To Limit The Bandwidth Used By Scp Command ?

Answer :

We can limit the bandwidth used by the scp command using the -l alternative as shown inside the syntax.’#scp -l bandwidth restriction filename username@far off-host:/folder-name’ , wherein bandwidth restriction is numeric to be laid out in kilobits consistent with 2d.

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Question thirteen. How To Enable Passwordless Ssh Authentication In Linux ?

Answer :

To Implement passwordless or Keys primarily based authentication we ought to generate Public and Private keys , Copy the Pubic keys to faraway Linux servers both manually or with the aid of ssh-replica-identity command.Ssh-reproduction-id command will automatically reproduction the contents of id_rsa.Pub report to ‘~/.Ssh/authorized_keys’ record of faraway linux server.

Question 14. How To Check Ssh Server’s Version ?

Answer :

Using the command ‘ ssh -V ‘ we will discover the ssh server’s version.

Question 15. Please Explain The Different Protocols For Ssh Communication?

Answer :

SSH has  protocols, Protocol 1 and Protocol 2. Protocol 1 is much less comfy and old. We use Protocol 2 now-a-days! You can set/alternate it from the SSH configuration document.

Question sixteen. How To Check Ssh Server’s Version Details From Linux Commandline?

Answer :

You can find the SSH server model by executing the subsequent command:

# ssh -V

Example:

# ssh -V

OpenSSH_6.6.1p1, OpenSSL 1.Zero.1e-fips 11 Feb 2013.

Question 17. What Is Abbreviated As Scp?

Answer :

SCP stands for Secure Copy.

Question 18. Did You Hear About Blowfish?

Answer :

Blowfish is used with SCP command. It uses to boom the transfer velocity. By default scp makes use of the Triple-DES cipher to encrypt the records being copied.

Syntax: scp -c blowfish root@host:/domestic/crybit/* /domestic/crybit.

Question 19. Can You Briefly Explain The Working Of Scp?

Answer :

SCP stands for Secure Copy. It switch files over n/w securely. SCP is based on SSH protocol and it uses the SSH port by way of default.

Working principle:

Client initiates an SSH connection to the far off host, and requests an SCP technique to be began at the far off host.
Remote SCP system can operate in  modes.
2.1 Source mode

In this mode, SCP on far off host read files from HDD and send them returned to the consumer system.

2.Three Sink mode

Which be given the files sent by using the consumer and write them to the disk at the faraway host.

Syntax is identical because the base Linux copy command.

Question 20. What Purpose Is Assigned For “maxauthtries?”

Answer :

Which defines the most wide variety of allowed failed login attempt from a n/w.

Question 21. How Do You Access Gui Using Ssh Connection?

Answer :

SSH may even help of moving X11 forwarding, we need to use options referred to as -XY to open server GUI app from client.