Two way sync with lsyncd

[senthilvael]

Hi Team,
Some time back, I need to implement a 2 way sync between 2 servers. I searched in the internet and implemented it. The following link helped me 80% of the work. Any how wanted to write a step by step tutorial. Please let me know any points I missed or any corrections.

Source : Details of two-way sync between two Ubuntu machines | (R news & tutorials)

Environment
Server 1 = 1.2.3.4
Server 2 = 5.6.7.8
Un privilaged user on each server = one
Dir to Sync = /tmp/synctest

Step 1: Implement Password less ssh login between 2 servers
Server 1

one@server1:~> ssh-keygen -t rsa

Generating public/private rsa key pair.
Enter file in which to save the key (/home/one/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/one/.ssh/id_rsa.
Your public key has been saved in /home/one/.ssh/id_rsa.pub.
The key fingerprint is:
f6:61:a8:27:35:cf:4c:6d:13:22:70:cf:4c:c8:a0:23 one@server1

Copy the content of the file “home/one/.ssh/id_rsa.pub” to the following file on server2 “home/one/.ssh/authorized_keys”

Server 2

one@server2:~> ssh-keygen -t rsa

Generating public/private rsa key pair.
Enter file in which to save the key (/home/one/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/one/.ssh/id_rsa.
Your public key has been saved in /home/one/.ssh/id_rsa.pub.
The key fingerprint is:
f6:61:a8:27:35:cf:4c:6d:13:22:70:cf:5c:c8:a0:24 one@server2

Copy the content of the file “home/one/.ssh/id_rsa.pub” to the following file on server1 “home/one/.ssh/authorized_keys”
Now we can ssh between 2 server as one without any password.

Step2: Install lsyncd and Unison on both the servers (as root).
Server 1

root@server1 # mkdir /tmp/lsyncd
root@server1 # cd /tmp/lsyncd
root@server1 # wget http://lsyncd.googlecode.com/files/lsyncd-2.0.6.tar.gz
root@server1 # tar -zxvf lsyncd-2.0.6.tar.gz
root@server1 # cd lsyncd-2.0.6
root@server1 # aptitude install gcc pkg-config lua5.1 liblua5.1-0-dev liblua50-dev liblualib50-dev
root@server1 # ./configure
root@server1 # make
root@server1 # make install
root@server1 # aptitude install unison

Server 2

root@server2 # mkdir /tmp/lsyncd
root@server2 # cd /tmp/lsyncd
root@server2 # wget http://lsyncd.googlecode.com/files/lsyncd-2.0.6.tar.gz
root@server2 # tar -zxvf lsyncd-2.0.6.tar.gz
root@server2 # cd lsyncd-2.0.6
root@server2 # aptitude install gcc pkg-config lua5.1 liblua5.1-0-dev liblua50-dev liblualib50-dev
root@server2 # ./configure
root@server2 # make
root@server2 # make install
root@server2 # aptitude install unison

Step 3: Configure lsyncd (as the user one)
Server 1

one@server1:~$ mkdir /tmp/synctest
one@server1:~$ vim lsyncd.conf

settings = {
   logfile    = "/tmp/lsyncd.log",
   statusFile = "/tmp/lsyncd.status",
   maxDelays = 3
}
runUnison2 = {
maxProcesses = 1,
delay = 3,
onAttrib = "/usr/bin/unison -batch /tmp/synctest ssh://5.6.7.8//tmp/synctest",
onCreate = "/usr/bin/unison -batch /tmp/synctest ssh://5.6.7.8//tmp/synctest",
onDelete = "/usr/bin/unison -batch /tmp/synctest ssh://5.6.7.8//tmp/synctest",
onModify = "/usr/bin/unison -batch /tmp/synctest ssh://5.6.7.8//tmp/synctest",
onMove = "/usr/bin/unison -batch /tmp/synctest ssh://5.6.7.8//tmp/synctest",
}


sync{runUnison2, source="/tmp/synctest"}

Server 2

one@server2:~$ mkdir /tmp/synctest
one@server2:~$ vim lsyncd.conf

settings = {
   logfile    = "/tmp/lsyncd.log",
   statusFile = "/tmp/lsyncd.status",
   maxDelays = 3
}
runUnison2 = {
maxProcesses = 1,
delay = 3,
onAttrib = "/usr/bin/unison -batch /tmp/synctest ssh://1.2.3.4//tmp/synctest",
onCreate = "/usr/bin/unison -batch /tmp/synctest ssh://1.2.3.4//tmp/synctest",
onDelete = "/usr/bin/unison -batch /tmp/synctest ssh://1.2.3.4//tmp/synctest",
onModify = "/usr/bin/unison -batch /tmp/synctest ssh://1.2.3.4//tmp/synctest",
onMove = "/usr/bin/unison -batch /tmp/synctest ssh://1.2.3.4//tmp/synctest",
}


sync{runUnison2, source="/tmp/synctest"}

Step 4: Start lsyncd, Monitor the logs make sure all the sync is going good
Server 1

one@server1:~$ lsyncd -log Exec lsyncd.conf
one@server1:~$ -ef|grep lsync

livesync   998     1  0 05:37 ?        00:00:00 lsyncd -log Exec lsyncd.conf
livesync  4512   529  0 07:05 pts/0    00:00:00 grep lsync

one@server1:~$ tail -f /tmp/lsyncd.log

Server2

one@server2:~$ lsyncd -log Exec lsyncd.conf
one@server2:~$ ps -ef |grep lsyncd

livesync 16939     1  0 21:38 ?        00:00:00 lsyncd -log Exec lsyncd.conf
livesync 17261 17241  0 23:10 pts/3    00:00:00 grep lsyncd

one@server2:~$ tail -f /tmp/lsyncd.log

Note: 1. Never Keep the sync log inside the dir which is going to be synced. It will leads to continuous sync.
2. If you delete all files in any of the server, the Unison will stop working (Its due to the default behaviour).