RSYNC Setup for Offiste Backup Copying | Linux

Summary
Run RSYNC for Offsite Backup copying from SiteA-Server to SiteB-Server


How-to
1. Create an Account on SiteB-Server

useradd {USERNAME}
passwd {USERNAME}

2. Create an RSA Asymmetric Key on SiteA-Server:

# Private Key: ~/.ssh/id_rsa
# Public Key: ~/.ssh/id_rsa.pub
#
#@ref https://en.wikipedia.org/wiki/Key_size#Asymmetric_algorithm_key_lengths
ssh-keygen -b 4096 -t rsa

Generating public/private rsa key pair.
Enter file in which to save the key (/home/UserA/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/UserA/.ssh/id_rsa.
Your public key has been saved in /home/UserA/.ssh/id_rsa.pub.
The key fingerprint is: {KEY}
The key's randomart image is:
+--[ RSA 4096]----+
|                  |
|   [.........]    |
|                  |
+-----------------+

Copy the public key to SiteB-Server, then:

scp ~/.ssh/id_rsa.pub UserB@SiteB-Server

Or:

scp ~/.ssh/id_rsa.pub UserB@SiteB-Server:~/.ssh/authorized_keys

3. Set the authorized key, and sshd on SiteA-Server

touch ~/.ssh/authorized_keys

cat ~/id_rsa.pub >> ~/.ssh/authorized_keys

rm ~/id_rsa.pub

chmod 700 ~/.ssh

chmod 600 ~/.ssh/authorized_keys

Edit /etc/ssh/sshd_config. Only allow UserB from SiteA-Server:

PubkeyAuthentication yes
AuthorizedKeysFile .ssh/authorized_keys

AllowUsers UserB@SiteB-Server

4. Set RSYNC to run the task daily on SiteB-Server

crontab -e
0  23  *  *  *  rsync -avz -e "ssh -p22" --del /backup-storage/ UserB@SiteA-Server:/backup-storage/ > /dev/null 2>&1

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