Ubuntu – Using tar and rsync for high availability


I have Ubuntu cloud servers running which I don't have direct access to but with ssh. I'm using 'tar' to clone or to have high availability of this server. I followed the tutorial from the link [link text][1]. I tried this installing a new server of same version. When I extracted the tar (tar -xvpzf ~/clone.tgz -C /) on the destination (new), at the end it's ending with the following output similar to the below (don't know if it's error).

tar: var/run: time stamp 2010-11-09 17:09:11 is 7335.159880406 s in the future
tar: var/spool/postfix/usr/lib/zoneinfo: time stamp 2010-11-09 17:08:26 is 7290.159730037 s in the future
tar: var/lib: time stamp 2010-11-09 17:27:51 is 8455.159349527 s in the future
tar: usr/bin: time stamp 2010-11-09 17:28:02 is 8466.159254097 s in the future
tar: usr/share/sgml: time stamp 2010-11-09 17:27:47 is 8451.158909506 s in the future
tar: usr/share/man/man7: time stamp 2010-11-09 17:27:50 is 8454.158393583 s in the future
tar: usr/share/man/man1: time stamp 2010-11-09 17:28:02 is 8466.158166556 s in the future
tar: usr/share/man/man8: time stamp 2010-11-09 17:27:51 is 8455.158057701 s in the  future
tar: usr/share/omf/time-admin: time stamp 2010-11-09 17:27:52 is 8456.157830449 s in the future

I'm using following command to create a tar file of the specified directories on the source system.

tar -cvzf ~/clone.tgz --exclude ~/clone.tgz --exclude /etc/hosts --exclude /etc/hostname --exclude /etc/udev/ --exclude /etc/network/interfaces --exclude /etc/resolv.conf  /etc /home /opt /tmp /usr /var /mnt
  • Is there any precautions before using tar? (the tar is one time creation from then I'll be using rsync)
  • Should I've to include any more directory like bin or lib? – suggest me
  • Should I've to exclude any directory? Like I had a network device (eth0) problem (failed to start up eth0). So in the above command I've excluded "/etc/udev/" and after this I felt this was fine. Like this, is there any thing I've to exclude from /etc/ or from any directory that I've included? – suggest me.
  • How could I schedule rsync (incremental bkp) with ssh combination to sync the directories (specified in tar) to the remote location (say /mnt/newdir) which I could tar and extract it later in case of system failure. Rsync can be scheduled to run as root user but the ssh will prompt for the password. FYI, sudo is completely disabled and as well as direct ssh login to root is also disabled.

If there is any better way without any harm to server to achieve this, can suggest.

[1]: http://ubuntuforums.org/showthread.php? t=525660

Best Answer

I would recommend you to use rsync instead, it will allow you to do a live system to system real synchronization without the need of temporary files. It also provides the benefit of doing incremental updates when you need to update the clone.

I would exclude only: /proc/ /sys /dev /tmp /mnt On the clone system you will need to make sure /etc/fstab and /boot/grub/grub.cfg are updated with the UUIDs of the clone systems partitions.

If you have a database like mysql you will need to be carefull and stop the DB before performing the copy.

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