How to keep two folders automatically synchronized

Question

I would like to have a synchronized copy of one folder with all its subtree   It should work automatically in this way  whenever I create  modify  or delete stuff from the original folder those changes should be automatically applied to the sync-folder   Which is the best approach to this task   BTW  I m on Ubuntu 12 04  Final goal is to have a separated real-time backup copy  without the use of symlinks or mount  I used Ubuntu One to synchronize data between my computers  and after a while something went wrong and all my data was lost during a synchronization   So I thought to add a step further to keep a backup copy of my data    I keep my data stored on a  folder A  I need the answer of my current question to create a one-way sync of  folder A  to  folder B   cron a script with rsync  could be    I need it to be one-way only from A to B any changes to B must not be applied to A  The I simply keep synchronized  folder B  with Ubuntu One  In this manner any change in A will be appled to B  which will be detected from U1 and synchronized to the cloud  If anything goes wrong and U1 delete my data on B  I always have them on A    Inspired by lanzz s comments  another idea could be to run rsync at startup to backup the content of a folder under Ubuntu One  and start Ubuntu One only after rsync is completed   What do you think about that  How to know when rsync ends

User · Answer

I use this free program to synchronize local files and directories: https://github.com/Fitus/Zaloha.sh. The repository contains a simple demo as well.

The good point: It is a bash shell script (one file only). Not a black box like other programs. Documentation is there as well. Also, with some technical talents, you can "bend" and "integrate" it to create the final solution you like.

User · Answer

You need something like this  https   github com axkibe lsyncd It is a tool which combines rsync and inotify - the former is a tool that mirrors  with the correct options set  a directory to the last bit  The latter tells the kernel to notify a program of changes to a directory ot file   It says        It aggregates and combines events for a few seconds and then spawns one  or more  process es  to synchronize the changes     But - according to Digital Ocean at https   www digitalocean com community tutorials how-to-mirror-local-and-remote-directories-on-a-vps-with-lsyncd - it ought to be in the Ubuntu repository   I have similar requirements  and this tool  which I have yet to try  seems suitable for the task

User · Answer

Just simple modification of  silgon answer   while true  do    inotifywait -r -e modify create delete  directory   rsync -avz  directory  target done     silgon version sometimes crashes on Ubuntu 16 if you run it in cron

User · Answer

You can take advantage of fschange  It   s a Linux filesystem change notification   The source code is downloadable from the above link  you can compile it yourself  fschange can be used to keep track of file changes by reading data from a proc file   proc fschange   When data is written to a file  fschange reports the exact interval that has been modified instead of just saying that the file has been changed   If you are looking for the more advanced solution  I would suggest checking Resilio Connect   It is cross-platform  provides extended options for use and monitoring  Since it   s BitTorrent-based  it is faster than any other existing sync tool  It was written on their behalf

User · Answer

You can use inotifywait  with the modify create delete move flags enabled  and rsync  while inotifywait -r -e modify create delete move  directory  do     rsync -avz  directory  target done  If you don t have inotifywait on your system  run sudo apt-get install inotify-tools

[bash] How to keep two folders automatically synchronized?

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