Introduction to the method of real-time synchronization of two servers under Linux

Assume the following requirements:

Assume two servers:

192.168.0.1 The source server has the directory /opt/test/

192.168.0.2 The target server has the directory /opt/bak/test/

The purpose of implementation is to maintain real-time synchronization of a certain file directory of the two servers

Implementation method: Achieved through the combination of rsync+inotify-tools

Preparation work:

First of all, you need to add a trust relationship to the two machines. The specific method has been introduced in the previous article

View details: linux adds trust relationship without password login

Need to install software:

1. rsync synchronization software

Needs to be installed on both the source server and target server

Source server: It is an rsync client, not required Configuration

Target server: It is the rsync server. You need to configure the contents in /etc/rsyncd.conf

2. inotify-tools tool

This tool is for real-time file monitoring The tool requires Linux operating system kernel support, and kernel support requires at least version 2.6.13

Check whether the operating system supports it, execute as follows:

uname -r View version

Return:

    2.6.32-358.6.1.el6.x86_64

It means that version 2.6.32 is greater than 2.6.13, and it is supported.

Execution:

    ll /proc/sys/fs/inotify
    total 0
    -rw-r--r-- 1 root root 0 Oct 18 12:18 max_queued_events
    -rw-r--r-- 1 root root 0 Oct 18 12:18 max_user_instances
    -rw-r--r-- 1 root root 0 Oct 18 12:18 max_user_watches

If there are three outputs, it means that inotify is supported by default and you can install the inotify-tools tool.

If it is not supported, you need to use a new version of the linux operating system

If the version meets the requirements, it can be installed.

After installing inotify-tools, the following two files will be generated in the relevant installation directory:

    ll /usr/local/bin/
    total 88
    -rwxr-xr-x 1 root root 44327 Oct 10 15:32 inotifywait
    -rwxr-xr-x 1 root root 41417 Oct 10 15:32 inotifywatch

It means the installation is successful.

Note: It needs to be installed on the source server, and inotify does not need to be installed on the target server.

3. Related scripts:

Create a new script on the source server:

inotify_bak.sh

    #!/bin/bash
    src=/opt/test/
    /usr/local/bin/inotifywait -mrq --timefmt '%d/%m/%y %H:%M' --format '%T %w%f%e' -e close_write,delete,create,attrib $src |  while read file
    do
          /usr/bin/rsync -arzuq $src 192.168.0.1::www/
          echo "  ${file} was rsynced" >>/opt/soft/log/rsync.log 2>&1
    done

Grant execution permissions: chmod +x inotify_bak.sh

Then execute: nohup inotify_bak.sh & Put it in the background for execution

4. About starting

Target server: Start the rsync background service first: / usr/bin/rsync --daemon

Source server: Execute inotify_bak.sh &

5. Test:

Create a new directory and file in the source server directory, inotify_bak. The sh script will detect it and then synchronize it to the relevant directory of the target server

You can view the log file: /opt/soft/log/rsync.log The command is as follows: observe the real-time synchronization situation.

    tail -f  /opt/soft/log/rsync.log

Error resolution:

/usr/local/bin/inotifywait: error while loading shared libraries: libinotifytools.so.0: cannot open shared object file: No such file or directory

This is because the library file cannot be found. Just make a soft connection

ln -s /usr/local/lib/libinotifytools.so.0 /usr/lib64/libinotifytools.so.0

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