2 Way Syncing between 2 Servers using lsyncd

Requirements

1. At least 2 servers
2. lsyncd installed on both servers
3. ssh access between both servers

Assumptions

1. username for both servers is: forge
2. IP for server #1: 111.111.111
3. IP for server #2: 222.222.222
4. Folder to sync between the 2 servers (can be different, this example both same path and directory): syncro
5. SSH key (can be different, this example same key name): syncro_key

Setup

This setup is for server #1, to setup server #2 it's the same. Just see the comments in the code in step #4

1. Install lsyncd
   • sudo apt install lsyncd
2. Create lsyncd log folder
   • sudo mkdir /var/log/lsyncd
3. Create log and status files
   • sudo touch /var/log/lsyncd/lsyncd.{log,status}

4. Create config file

   • sudo nano /etc/lsyncd.conf.lua
   • Note: Anything after -- are comments in the code

   -- server #1 setup
   settings {
         logfile = "/var/log/lsyncd/lsyncd.log", -- location of log file created in step 3
         statusFile = "/var/log/lsyncd/lsyncd.status", -- location of status file created in step 3
   }
   
   targetlist = {
       "forge@222.222.222:/home/forge/syncro", -- server #2 will have target forge@111.111.111
   }
   
   for _, server in ipairs( targetlist ) do
       sync {
           default.rsync,
           source = "/home/forge/syncro", -- folder which to sync from
           target = server,
           delete = 'running',
           rsync = {
               rsh = "ssh -i /home/forge/.ssh/syncro_key", -- ssh key
               update = true,
               archive = true,
               compress = true,
           }
       }
   end
   

5. Start the lsyncd service

   • sudo service lsyncd start

6. Set the config lsyncd service will use

   • sudo lsyncd /etc/lsyncd.conf.lua
   • IMPORTANT When the server restarts run this again

Notes

There is a limit to how many files/folders that can be watched

• To check the current limit:
  • cat /proc/sys/fs/inotify/max_user_watches
• To permanently alter the limit : (500000 is an example number)
  • sudo sysctl fs.inotify.max_user_watches=500000