How to use OpenSSH in Redhat/Centos Part 2

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OpenSSH Configuration and Usage Part 2

Hi guys in our previous tutorial we have learnt and practiced few ssh commands (different switches).Today we will continue with ssh utility and transfer files with secure environment.  In this tutorial we will learn commands with options like ssh with wall option, scp –P, scp –r and scp –C, scp –c.

Broadcasting a Message to a System

The following example sends a message on the remote system. Syntax ssh username@hostname/IP wall “type your message here”.

Message sent from server

[Server@faraz ~]$ ssh Client@ wall "Hi, It is informed you that i am using wall Msg"

Clinet@'s password:

[Server@faraz ~]$

Message received in client machine

Broadcast message from Faraz@faraz.test.server (Wed Feb  3 13:31:47 2016):

Hi, It is informed you that i am using wall Msg

Secure Copy SCP

SCP means of securely transferring files using the secure shell (SSH) protocol between a local computer and a remote host and between two remote hosts. This utility uses same authentication mechanism as SSH.
To run a secure shell on or securely copy a file to/from a remote system you need to sure that you have following criteria. The remote system must be running sshd daemon such as OpenSSH, you must have an account on the remote system and the server must positively identify the client.

SCP for Local System to Remote System

Copy files from local system to remote system by using command SCP. Syntax is scp path_of _source_file   user@to-host:path_of_destination_file (where you want to paste that file)

[Server@faraz ~]$ scp /home/Server/filetransfer.txt  Client@

Client@'s password:

filetransfer.txt                                                         100% 1631     1.6KB/s   00:00

[Server@faraz ~]$ ssh Client@

Client@'s password:

Last login: Wed Feb  3 13:01:00 2016 from

[Client@faraz ~]$ ls

Desktop  Documents  Downloads  filetransfer.txt  Music  Pictures  Public  ssh.config  Templates  testfile.txt  Videos

[CLient@faraz ~]$

SCP for Remote System to Local System

Copy files from remote system to local system by using SCP command. Syntax is scp user@from-host:path_of_source_file path_of _destination_file

[Server@faraz ~]$ scp Client@  /home/Server/

Client@'s password:

testfile.txt                                        100%   79     0.1KB/s   00:00

[Server@faraz ~]$ ls

1234  Desktop  Documents  Downloads  historysave.txt  Music  newstring.file  Pictures  Public  Templates  testfile.txt  Videos

[Server@faraz ~]$

SCP for Remote System to Remote System

This command is very useful when you are going to copy file remote system to another remote system on a network. Copy files from remote to remote system by using SCP command. Syntax is scp user@from-host: path_of_source_file  user@to-host:path_of_destination_file

[Server@faraz ~]$ scp abc@     Client@

abc@'s password:

Client@'s password:

123abc.txt                                                    100%   76     0.1KB/s   00:00

Connection to closed.

[Server@faraz ~]$

SCP with some Useful options

-P (in Caps) option is used to connect to the port number if you changed the default port

Syntax : scp –P port_no  source_file  user@to-host:path_of_destination_file

[Client@faraz ~]$ scp -P 122 historysave.txt Server@

Server@'s password:

historysave.txt                               100%   29MB  3.1MB/s   00:09

[Client@faraz ~]$

-r option is used to recursively (procedure to successive results) copy directory with all its contents(files/subdirectories)

Syntax scp –r  file/dir user@to-host:path_of_destination

[Server@faraz ~]$ scp -r Documents Client@

Client@'s password:

testfile.txt                                  100%   79     0.1KB/s   00:00

string.file                                   100%   76     0.1KB/s   00:00

[Server@faraz ~]$ ssh Client@ ls /home/Client/Desktop

Client@'s password:



[Server@faraz ~]$

-C (in caps) is used to compress the file to make transfer faster than normal transfer.

Syntax scp –C file-name user@to-host:path_of_destination.

First command transferred file in 9 seconds .Second one transfered file (compressed) in 2 seconds

[Server@faraz ~]$ scp  historysave.txt Client@

Client@'s password:

historysave.txt                               100%   29MB  3.1MB/s   00:09

[Server@faraz ~]$ scp -C historysave.txt Client@

Client@'s password:

historysave.txt                               100%   29MB  20.9MB/s   00:02

[Server@faraz ~]$

-c is used for encrypt the session of file to transfer on other system. Syntax scp –c ciper file-name  user@to-host:path_of_destination

[Server@faraz ~]$ scp -c 3des newstring.file Client@

Client@'s password:

newstring.file                                100%   76     0.1KB/s   00:00

[Server@faraz ~]$

In this tutorial we learnt scp command with useful options –P, -r, -C and –c.  I hope you enjoyed part2 .We will discuss more commands in our next tutorial part3


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