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SSH Key-Pair Authentication

SSH Passwordless Login in Linux

First login into server 192.168.0.12 with user tecmint and generate a pair of public keys using the following command.

Step 2:    Upload SSH Key to – 192.168.0.11

Use SSH from server 192.168.0.12 and upload a new generated public key (id_rsa.pub) on server 192.168.0.11 under sheena‘s .ssh directory as a file name authorized_keys.

#  ssh-copy-id sheena@192.168.0.11

Step 3:    Test SSH Passwordless Login from 192.168.0.12

From now onwards you can log into 192.168.0.11 as sheena user from server 192.168.0.12 as a tecmint user without a password.

# ssh sheena@192.168.0.11

 ------------------X----------------------

SSH Login Without Password on CentOS and RHEL.

This steps tested on CentOS 5/6/7, RHEL 5/6/7 and Oracle Linux 6/7.

Node1 : 192.168.0.9      -> Local Server

Node2 : 192.168.0.10     -> Remot  Server

Step One : Test the connection and access from node1 to node2 :

[root@node1 ~]#      ssh root@192.168.0.10

The authenticity of host '192.168.0.10 (192.168.0.10)' can't be established.

RSA key fingerprint is 6d:8f:63:9b:3b:63:e1:72:b3:06:a4:e4:f4:37:21:42.

Are you sure you want to continue connecting (yes/no)? yes

Warning: Permanently added '192.168.0.10' (RSA) to the list of known hosts.

root@192.168.0.10's password:

Last login: Thu Dec 10 22:04:55 2015 from 192.168.0.1

[root@node2 ~]#

Step Two : Generate public and private keys using ssh-key-gen. Please take note that you can increase security by protecting the private key with a passphrase.

[root@node1 ~]#  ssh-keygen

Step Three :  Copy or transfer the public key to remote-host using ssh-copy-id command. It will append the indicated identity file to ~/.ssh/authorized_keys on node2 :

[root@node1 ~]#      ssh-copy-id -i ~/.ssh/id_rsa.pub 192.168.0.10

root@192.168.0.10's password:

Now try logging into the machine, with "ssh '192.168.0.10'", and check in:

.ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.

Step Four : Try SSH login without Password to node2 :

[root@node1 ~]#     ssh root@192.168.0.10

Last login: Sun Dec 13 14:03:20 2015 from www.ehowstuff.local

I hope this article gives you some ideas and quick guide on how to setup SSH login without password on Linux CentOS / RHEL.

            ------------------------------------------------

# ssh root@192.168.0.1 -p 2244 

#  scp -r root@192.168.123.33:/root/Music/* /root/zz/ 

# scp -P 2322 file.txt  remote_username@10.10.0.2:/remote/directory 

 remote server IP                                 TO        own server

scp -r root@203.169.11.254:/home/u1/Maildir/new/*  /home/u1/Maildir/new/

                      Remote server IP                                 TO        own server

scp -r root@worldcm.net:/home/kamal/Maildir/cur/*  /home/u1/Maildir/cur/                   --> # inbox mail [ mail show Runing Time]

chown -R u1:u1 /home/u1/Maildir/cur/              -->#[own server]

# cd /home                   [ if mail box coppy]

chown -R mamun:mamun mamun

/home/mamun/Maildir/cur       [mail inbox ]

/home/mamun/Maildir/.Sent/cur    [send mail]

                           -------------Rsync ---------------

 Copying the SSH-Key to the Remote Host

#  ssh-copy-id -i /root/.ssh/id_rsa.pub root@mail.abcd.com               [ copy file to remote server]

 # ssh-copy-id -i /root/.ssh/authorized_keys root@mail.abcd.com

     Port:  2526

ssh-copy-id -i /root/.ssh/id_rsa.pub  '-p 2526 root@192.168.117.2'

ssh-copy-id -i /root/.ssh/authorized_keys  '-p 2526 root@192.168.117.2'

                         Verifying the Login Without Password

 # ssh root@mail.abcd.com        [no need passwd]

Simple File Transfer Examples

Directory File Transfer

# rsync -rt /home/transfer_me root@x.x.x.x:/home

Copy/Sync a Directory on Local Computer

# rsync -avzh /root/rpmpkgs /tmp/backups/

Copy a Directory from Local Server to a Remote Server

# rsync -avzh /root/rpmpkgs root@192.168.0.141:/root/

# rsync -avzh root@192.168.0.141:/root/rpmpkgs /tmp/myrpms

# rsync -avzhe ssh root@192.168.0.141:/root/anaconda-ks.cfg /tmp

  rsync -avzhe ssh root@103.182.196.55:/home/accesstel/Maildir/cur/*.*  /home/accesstel/Maildir/cur

  rsync -avzhe ssh root@103.182.196.55:/home/accesstel/Maildir/.Sent/cur/*.* 

                   ----------------------------

   rsync -avzhe 'ssh -p 7575' root@192.168.117.2:/home/ithelpdesk/Maildir/cur/*.*  /home/ithelpdesk/Maildir/cur

  rsync -avzhe 'ssh -p 7575' root@192.168.117.2:/home/ithelpdesk/Maildir/.Sent/cur/*.*  /home/ithelpdesk/Maildir/.Sent/cur

 /home/accesstel/Maildir/.Sent/cur

# rsync -v -e 'ssh -p1070' root@10.10.10.2:/home/test.txt  /home

# rsync -v -e 'ssh -p2222' /home/test.txt  root@10.10.10.2:/home

                               ----- Coppy Fron remote Server to Client--------------------

rsync -arvz -e "ssh -p 7575" root@192.168.123.33:/root/Music/*  /root/zz/

rsync -arvzhe "ssh -p 7575" root@192.168.123.33:/root/Music/*  /root/zz/

-------------------

scp -r root@192.168.123.33:/root/Music/* /root/zz/

Step 4: Connect to SSH server on port # 2022 using SSH command:

ssh -p PortNumberHere user@server-name-here

ssh -p PortNumberHere user@server-name-here commandNameHere

ssh -p 2022 XYZ@192.168.1.5

ssh -p 2022 XYZ@192.168.1.5 df

To connect to an SSH server on port # 2022 using scp command type:

scp -P PortNumberHere source user@server-name-here:/path/to/dest

scp -P 2022 resume.pdf XYZ@nas01:/backups/personal/XYZ/files/

To connect to an SSH server on port # 2022 using sftp command type:

sftp -P PortNumberHere user@server-name-here

sftp -P 2022 XYZ@192.168.1.5

To connect to SSH server on port # 2022 using rsync command type:

Change SSH port number with rsync command:

sync -av -e 'ssh -p PORT-NUMBER-HERE' source user@server-name

So, to backup /home/XYZ to server1.XYZ.net.in at port number 2022, enter:

rsync -av -e 'ssh -p 2022' /home/XYZ/ backupop@server1.XYZ.net.i

# create key-pair

[cent@dlp ~]$ ssh-keygen

Generating public/private rsa key pair. Enter file in which to save the key (/home/cent/.ssh/id_rsa):   # Enter or input changes if you want Created directory '/home/cent/.ssh'. Enter passphrase (empty for no passphrase):   # set passphrase (if set no passphrase, Enter with empty) Enter same passphrase again: Your identification has been saved in /home/cent/.ssh/id_rsa. Your public key has been saved in /home/cent/.ssh/id_rsa.pub. The key fingerprint is: SHA256:+EGzR05q/tnbBNmyaPOfsipDYz9ZAD6OrH4VmzfssPY cent@dlp.srv.world The key's randomart image is: ..... ..... 

[cent@dlp ~]$ ll ~/.ssh

total 8 -rw-------. 1 cent cent 1876 Sep 29 20:34 id_rsa -rw-r--r--. 1 cent cent  400 Sep 29 20:34 id_rsa.pub 

[cent@dlp ~]$ mv ~/.ssh/id_rsa.pub ~/.ssh/authorized_keys

[cent@node01 ~]$ mkdir ~/.ssh

[cent@node01 ~]$ chmod 700 ~/.ssh

# transfer the private key to the local ssh directory

[cent@node01 ~]$ scp cent@dlp.srv.world:/home/cent/.ssh/id_rsa ~/.ssh/

cent@dlp.srv.world's password: id_rsa                                        100% 1876   193.2KB/s   00:00 

[cent@node01 ~]$ ssh cent@dlp.srv.world

Enter passphrase for key '/home/cent/.ssh/id_rsa':   # passphrase if you set Activate the web console with: systemctl enable --now cockpit.socket  Last login: Sun Sep 29 20:33:58 2019

[cent@dlp ~]$   # logined

[root@dlp ~]# vi /etc/ssh/sshd_config

# line 73: change to [no]

PasswordAuthentication no

[root@dlp ~]# systemctl restart sshd

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