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Automate backup with rsync over ssh and crond

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rsync over ssh provides an excellent way to automate your backups

Here I show you how a backup of my cvs-repository is daily updated on another machine. You can of course backup any directory this way.

We have two machines, one with the data and one where we want to put the backup of the data on. Below we follow the following aliasses for these machines:

  • <localhost> : the machine that has the data
  • <remotehost> : the machine we want to put the backup on

Replace these with your own machine-names or ip-numbers.

Automate ssh login

Generate key pair

Create a keypair on <localhost>. Login in this machine as the user you want to do the backup:

ssh-keygen -t rsa                                                       
Generating public/private rsa key pair.
Enter file in which to save the key (/home/matto/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/matto/.ssh/id_rsa.
Your public key has been saved in /home/matto/.ssh/id_rsa.pub.

Copy public key to remotehost

cd .ssh
scp id_rsa.pub <remotehost>:.ssh/<localhost>_rsa.pub

Replace these with your own machine-names or ip-numbers. <remotehost> is the name or ip-number of your remotehost you want to login to. So if your localhost is known as gandalf remote host as frodo then the command is:

scp id_rsa.pub gandalf:.ssh/frodo_rsa.pub

Import the public key in the autorized_keys file

Login to <remotehost>

cd .ssh
cat <localhost>_rsa.pub >> authorized_keys

Test connection

After this you should be able to make a ssh connecton from <localhost> to <remotehost> without being required to give a password.

By renaming id_rsa.pub to <localhost>_rsa.pub it is easier to manage multiple keys.

Backup the data with rsync

First we try a rsync run. If everything goes well, we will scedule and perform updates with the help of crond in the next step.

/usr/bin/rsync -avz -e ssh /var/cvsroot/ <remotehost>:/var/backup/cvsroot/
This command copies the content of /var/cvsroot/ to the directory /var/backup/cvsroot/ on <remotehost>. You can of course use different paths. Take care of the usage of the trailing /, rsync is picky about this.

Create a crontab entry

Use crond to automate the backup process for you.

Edit the contrab file with the command crontab -e. Add a line:

8 3 * * *  /usr/bin/rsync -avz -e ssh /var/cvsroot/ <remotehost>:/var/backup/cvsroot/
At 8 minutes past 3 crond will perform the rsync process for you.

Tune the rsync command to your needs

When a file on <localhost> is removed (deleted) it will not automaticly be deleted on <remotehost>. This behaviour of rsync depends on the command you have given.

If you want deleted files also to be deleted on your rsynced backup, then add the switch "--delete" to the rsync command.

/usr/bin/rsync -avz --delete -e ssh <source> <remotehost>:<destiny>