Bidirectional file sync in RHEL 8 (csync2 + lsyncd)

Posted 2022-08-18 wemux

Csync2 installation and setup

Add below to /etc/hosts

10.30.11.11 app1
10.30.11.12 app2
10.30.11.13 app3

Install Csync2 Repository

rpm -ivh http://repo.okay.com.mx/centos/8/x86_64/release/okay-release-1-5.el8.noarch.rpm

install required packages

yum install xinetd sqlite-devel csync2

create backup directory

mkdir -p /var/csync2/backup

create the authentication key on app1

csync2 -k /etc/csync2.key

add below content to the configuration file /etc/csync2_ebanking.cfg

nossl * *;
group ebanking_media

        host app1 app2 pp3;
        key /etc/csync2.key;
        include /mnt/ebanking_media;
        auto younger;
        backup-directory /var/csync2/backup;
        backup-generations 3;

Copy authentication key and configuration files to all servers

scp /etc/sync2.key,csync2_ebanking.cfg bda-cbs-ebprdapp2:/etc/
scp /etc/sync2.key,csync2_ebanking.cfg bda-cbs-ebprdapp3:/etc/

Lsyncd installation and setup

Install EPEL Repository

dnf install -y https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm

update the system

dnf update -y

Search for the lsyncd package

dnf --disablerepo="*" --enablerepo="epel" list available | grep lsyncd

Install lsyncd package

dnf install lsyncd

add below to /etc/lsyncd.conf with each servers

----
-- User configuration file for lsyncd.
--
-- Simple example for default rsync, but executing moves through on the target.
--
-- For more examples, see /usr/share/doc/lsyncd*/examples/
--
-- syncdefault.rsyncssh, source="/var/www/html", host="localhost", targetdir="/tmp/htmlcopy/"
settings 
        logident        = "lsyncd",
        logfacility     = "user",
        logfile         = "/var/log/lsyncd/lsyncd.log",
        statusFile      = "/var/log/lsyncd/status.log",
        statusInterval  = 1

initSync = 
        delay = 1,
        maxProcesses = 1,
        action = function(inlet)
                local config = inlet.getConfig()
                local elist = inlet.getEvents(function(event)
                        return event.etype ~= "Init"
                end)
                local directory = string.sub(config.source, 1, -2)
                local paths = elist.getPaths(function(etype, path)
                        return "\\t" .. config.syncid .. ":" .. directory .. path
                end)
                log("Normal", "Processing syncing list:\\n", table.concat(paths, "\\n"))
                spawn(elist, "/usr/sbin/csync2", "-C", config.syncid, "-x")
        end,
        collect = function(agent, exitcode)
                local config = agent.config
                if not agent.isList and agent.etype == "Init" then
                        if exitcode == 0 then
                                log("Normal", "Startup of ", config.syncid, " instance finished.")
                        elseif config.exitcodes and config.exitcodes[exitcode] == "again" then
                                log("Normal", "Retrying startup of ", config.syncid, " instance.")
                                return "again"
                        else
                                log("Error", "Failure on startup of ", config.syncid, " instance.")
                                terminate(-1)
                        end
                        return
                end
                local rc = config.exitcodes and config.exitcodes[exitcode]
                if rc == "die" then
                        return rc
                end
                if agent.isList then
                        if rc == "again" then
                                log("Normal", "Retrying events list on exitcode = ", exitcode)
                        else
                                log("Normal", "Finished events list = ", exitcode)
                        end
                else
                        if rc == "again" then
                                log("Normal", "Retrying ", agent.etype, " on ", agent.sourcePath, " = ", exitcode)
                        else
                                log("Normal", "Finished ", agent.etype, " on ", agent.sourcePath, " = ", exitcode)
                        end
                end
                return rc
        end,
        init = function(event)
                local inlet = event.inlet;
                local config = inlet.getConfig();
                log("Normal", "Recursive startup sync: ", config.syncid, ":", config.source)
                spawn(event, "/usr/sbin/csync2", "-C", config.syncid, "-x")
        end,
        prepare = function(config)
                if not config.syncid then
                        error("Missing syncid parameter.", 4)
                end
                local c = "csync2_" .. config.syncid .. ".cfg"
                local f, err = io.open("/etc/" .. c, "r")
                if not f then
                        error("Invalid syncid parameter: " .. err, 4)
                end
                f:close()
        end

local sources = 
        ["/mnt/ebanking_media"] = "ebanking"

for key, value in pairs(sources) do
        sync initSync, source=key, syncid=value
end

Start and enable xinetd and lsyncd services

systemctl enable -- now xinetd
systemctl enable -- now lsyncd