Type the following commands:

1. ssh-keygen

   Press Enter key till you get the prompt

2. ssh-copy-id -i ~/.ssh/id_rsa.pub root@ip_address

   (It will once ask for the password of the host system)

3. ssh root@ip_address

Now you should be able to login without any password.

http://www.thegeekstuff.com/2008/11/3-steps-to-perform-ssh-login-without-password-using-ssh-keygen-ssh-copy-id/

Step 1: Create public and private keys using ssh-key-gen on local-host

jsmith@local-host$ [Note: You are on local-host here]

jsmith@local-host$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/jsmith/.ssh/id_rsa):[Enter key]
Enter passphrase (empty for no passphrase): [Press enter key]
Enter same passphrase again: [Pess enter key]
Your identification has been saved in /home/jsmith/.ssh/id_rsa.
Your public key has been saved in /home/jsmith/.ssh/id_rsa.pub.
The key fingerprint is:
33:b3:fe:af:95:95:18:11:31:d5:de:96:2f:f2:35:f9 jsmith@local-host

Step 2: Copy the public key to remote-host using ssh-copy-id

jsmith@local-host$ ssh-copy-id -i ~/.ssh/id_rsa.pub remote-host
jsmith@remote-host's password:
Now try logging into the machine, with "ssh 'remote-host'", and check in:

.ssh/authorized_keys

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

Note: ssh-copy-id appends the keys to the remote-host’s /home/user/.ssh/authorized_key.

Step 3: Login to remote-host without entering the password

jsmith@local-host$ ssh remote-host
Last login: Sun Nov 16 17:22:33 2008 from 192.168.1.2
[Note: SSH did not ask for password.]

jsmith@remote-host$ [Note: You are on remote-host here]


change the passphrase on your private key:
ssh-keygen -p

examples custom port and custom user:
ssh-copy-id "user@host -p 1234"

ssh-copy-id -i ~/.ssh/id_rsa.pub admin@domain.com -p 1234

root@linux:~# ssh-copy-id -i ~/.ssh/id_rsa.pub admin@remotehost -p 2222
Bad port 'umask 077; test -d ~/.ssh || mkdir ~/.ssh ; cat >> ~/.ssh/authorized_keys'

root@linux:~# cat ~/.ssh/id_rsa.pub | ssh admin@remotehost -p 2222 'umask 077; mkdir -p ~/.ssh; cat >> ~/.ssh/authorized_keys'
The authenticity of host '[remotehost]:2203 ([213.17.25.17]:2203)' can't be established.
RSA key fingerprint is 6e:c5:f3:6e:9a:07:87:28:fc:9f:0d:0d:a1:1a:02:2f.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[remotehost]:2222,[192.164.64.17]:2222' (RSA) to the list of known hosts.
admin@remotehost's password:
root@linux:~#

Generate a ssh key and disable password authentication on the Ubuntu 12.04 (Precise Pangolin) server

http://lani78.com/2012/07/21/generate-a-ssh-key-and-disable-password-authentication-on-ubuntu-server-12-0/

---

RSYNC CRONJOBS EXAMPLES

# Rsync Mirror Backup Directoy to remotepc
30 0    * * *    rsync --delete -avzpe ssh /backup/ root@remotepc:/backup/ >> /var/log/syncbackup-remotepc.log
0 1    * * *    rsync rsync --delete -azp -e 'ssh -p 22' /backup rsync.domain.com:/home/rsync

 

*/30 *    * * *    root /root/cronjobs/mirror.sh >> /tmp/output 2>&1

---

mirror.sh

#!/bin/bash
echo -e "\n" && date >> /var/log/mirror.log
rsync --delete -avzpe ssh /home/ root@remotepc:/home/ >> /var/log/mirror.log
exit

---

crontab
00 23    * * 4    root /cronjobs/syncfiles.sh >> /tmp/output 2>&1

syncfiles.sh
#!/bin/bash
mkdir -p /backup
tar -cvpzf /backup/$(date +%Y%m%d-%H%M)_$(hostname)_backupconfigfiles.tgz /etc /root
find /backup/ -type f -mtime +3 -name '*.tgz' -delete

# Script backup files to remote server

BACKUPDIRREMOTE=/backup/$(hostname)
ssh -p 2222 admin@remoteserver "mkdir -p $BACKUPDIR"

rsync -avzpe 'ssh -p 2222' /backup admin@remoteserver:$BACKUPDIRREMOTE
exit