Two good friends of rsync: `rsync+inotify-tools` & `rsync+sersync`

Using rsync for remote file real-time synchronization actually utilizes the daemon mode of rsync. This mode requires the installation of the application on the source server: rsync + inotify-tools or rsync + inotify-tools, and only rsync needs to be installed on the target server.

`rsync` Configuration Steps#

Server Information#

Target Server: 172.16.12.141
Source Server: 172.16.12.142

Target Server Configuration (Server-side Configuration)#

Create Configuration File: Modify `/etc/rsync.conf` to run in daemon mode#

RedHat7 and below CentOS7 do not have this by default, so it needs to be created manually.

Configuration File Explanation#

#rsyncd.conf Configuration File Explanation:

log file = /var/log/rsyncd.log    # Log file location, this file is automatically generated after starting rsync, no need to create it in advance
pidfile = /var/run/rsyncd.pid     # Location to store the pid file
lock file = /var/run/rsync.lock   # Lock file supporting max connections parameter
secrets file = /etc/rsync.pass    # User authentication configuration file, stores usernames and passwords, this file must be created manually

[etc_from_client]     # Custom synchronization name
path = /tmp/          # Path where rsync target server data is stored, data from the source server will be synchronized to this directory
comment = sync etc from client
uid = root        # Set rsync running permissions to root
gid = root        # Set rsync running permissions to root
port = 873        # Default port
ignore errors     # Indicates to ignore errors if they occur
use chroot = no       # Default is true, change to no to increase backup of directory file soft links
read only = no    # Set rsync source server to read-write permissions
list = no     # Do not display the rsync source server resource list
max connections = 200     # Maximum number of connections
timeout = 600     # Set timeout duration
auth users = admin        # Username for executing data synchronization, can set multiple, separated by commas in English
hosts allow = 192.168.110.12   # Allowed source server IP addresses for data synchronization, can set multiple, separated by commas in English
hosts deny = 192.168.110.11      # Prohibited source server IP addresses for data synchronization, can set multiple, separated by commas in English

Note: `host allow` and `host deny` Parameters#

Both parameters absent -- All users can access freely;
Only allow present -- Only users in the whitelist can access the module;
Only deny present -- Only users in the blacklist are prohibited from accessing the module;
Both parameters present -- Whitelist is checked first
- If matched successfully, access is allowed;
- If matching fails, check the blacklist; if matched successfully, access is denied;
- If neither matches, access is allowed.

Configuration File as Follows#

Note: The fake super = yes option was not present in earlier versions; in the new version, if this parameter is not added, a permission error will occur: rsync:chgrp ".hosts.G6sZha” (in backup) failed: Operation not permitted (1)

#rsyncd.conf Configuration File:

uid = rsync                # User for remote command using rsync to access shared directory
gid = rsync                # User group
use chroot = no            # Security related
max connections = 200      # Maximum number of connections
timeout = 300              # Timeout duration (how long to disconnect without backup)
pid file = /var/run/rsyncd.pid             # Process corresponding process ID file (stores the process ID during service operation)
lock file = /var/run/rsync.lock            # Lock file
log file = /var/log/rsyncd.log             # Log file, displays error information
fake super = yes 		   # Must add this in the new version
# Module Information:
[backup]                 # Custom module name
comment = "backup"
path = /backup/web       # Path corresponding to the module
ignore errors            # Ignore error programs
read only = false        # Whether it is read-only (here it is false, indicating it can be written)
list = false             # Whether it can list*
hosts allow = 172.16.12.0/24        # Allow access to rsync server client range (whitelist)
#hosts deny = 0.0.0.0/32            # Prohibit access to rsync server client range (blacklist)
auth users = rsync_backup          # Non-existent user, only for authentication
# Set the key file for connection authentication:
secrets file = /etc/rsync.password    # Key file for authentication

Create Password File, Change Permissions to `600`#

# Write password content to file
  echo "rsync_backup:123456" > /etc/rsync.password
  # For security, change the authentication user's password file permissions to 600
  chmod 600 /etc/rsync.password

Create System User#

# Create a virtual user for rsync, only used by the program
useradd rsync -s /sbin/nolgin -M

Create Corresponding Directory for the Module, and Change the Directory Owner and Group to the System User#

mkdir /backup/web
chown -R rsync.rsync /bakcup/

Start the `rsync` Daemon and Check if it Started#

rsync --daemon  # Start the daemon
ps -ef | grep rsync    # Check if the process has started
netstat -lntup | grep rsync # Check if it is listening on port 873

# Check if it has started normally and is listening on port 873
[root@fzfcdb ~]# ps -ef | grep rsync
root     19489     1  0 09:42 ?        00:00:00 rsync --daemon
root     27296 27115  0 15:09 pts/6    00:00:00 grep --color=auto rsync
[root@fzfcdb ~]# netstat -lntup | grep rsync
tcp        0      0 0.0.0.0:873             0.0.0.0:*               LISTEN      19489/rsync         
tcp6       0      0 :::873                  :::*                    LISTEN      19489/rsync         
[root@fzfcdb ~]#

Source Server Configuration#

Install `rsync` Software, Just Install, No Need to Start or Configure#

yum -y install rsync
# Confirm if rsync is installed
rpm -qa | grep rsync
rsync-3.1.2-10.el7.x86_64

Create Password File#

The client password file only needs the password, and the password file permissions should be 600

echo "123456" > /etc/rsync.password
# Set file owner to have read and write permissions
chmod 600 /etc/rsync.password

Source Server Upload to Server Test#

/www/ uploads all files from the local www folder to the server; if it is /www, it backs up the entire www folder;
rsync_backup is the auth users parameter in the server-side configuration file;
::backup is the module parameter and the [backup] in the configuration file, followed by the path to the configuration file's password file, allowing transfer without interaction, no need to enter a password.

rsync -avz /www/ [email protected]::backup --password-file=/etc/rsync.password

Source Server Download Test#

Download files from the backup module configured path on the server to the local www directory.

 rsync -avz [email protected]::backup --password-file=/etc/rsync.password /www

At this point, the rsync configuration is complete.

Use `inotify-tools` for Real-time Synchronization#

Install `inotify-tools`, Trigger `rsync` for Synchronization in Real-time#

# Check if the server kernel supports inotify
# If there are these three max-prefixed files, it indicates that the server kernel supports inotify
[root@localhost ~]# ll /proc/sys/fs/inotify/
total 0
-rw-r--r--. 1 root root 0 May 11 16:15 max_queued_events
-rw-r--r--. 1 root root 0 May 11 16:15 max_user_instances
-rw-r--r--. 1 root root 0 May 11 16:15 max_user_watches

# Install inotify-tools
yum -y install inotify-tools
# Check if installed
rpm -qa | grep inotify-tools
inotify-tools-3.21.9.6-1.16.el7.x86_64

Write Synchronization Script#

[root@localhost ~]# mkdir /scripts
[root@localhost ~]# touch /scripts/inotify.sh
[root@localhost ~]# chmod 755 /scripts/inotify.sh
[root@localhost ~]# ll /scripts/inotify.sh
-rwxr-xr-x 1 root root 0 Aug 10 13:02 /scripts/inotify.sh
[root@localhost ~]# vim /scripts/inotify.sh
host=172.16.2.4           # IP of the target server (backup server)
src=/www                       # Backup directory to monitor on the source server (this can be customized, but must exist)
des=backup             # Custom module name, must match the synchronization name defined on the target server
password=/etc/rsync.password        # Password file for executing data synchronization
user=rsync                      # Username for executing data synchronization
inotifywait=/usr/bin/inotifywait

$inotifywait -mrq --timefmt '%Y%m%d %H:%M' --format '%T %w%f%e' -e modify,delete,create,attrib $src \
| while read files;do
    rsync -avzP --delete  --timeout=100 --password-file=${password} $src $user@$host::$des
    echo "${files} was rsynced" >>/tmp/rsync.log 2>&1
done

Start the Script#

# & indicates to run in the background
nohup bash /scripts/inotify.sh &

Test: Generate a New File on the Source Server#

Check the `inotify` Generated Log#

Use `rsync+sersync` for Real-time Synchronization#

Introduction to `sersync`#

sersync is developed based on inotify, similar to inotify-tools. Therefore, the kernel must first support inotify to set it up.
sersync can record changes (including additions, deletions, modifications) to specific files or directories in the monitored directory, and when using rsync for synchronization, only the changed files or directories are synchronized.
Compared to inotify-tools, it traverses faster and has advantages when synchronizing large amounts of data, and it is quicker to set up without the need to write additional scripts.

Install `sersync`#

sersync is developed by a talented individual in China and cannot be installed using yum. It can be found directly on github or google code, and then installed manually.
Google code address: https://code.google.com/archive/p/sersync/
GitHub address: https://github.com/wsgzao/sersync

Source Server Configuration#

Download `sersync`#

wget https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/sersync/sersync2.5.4_64bit_binary_stable_final.tar.gz

Unzip to Get the Folder and Move/Rename It#

tar -zxvf sersync2.5.4_64bit_binary_stable_final.tar.gz 
# Move to /usr/local and rename to sersync
mv GUN-Linux-x86 /usr/local/sersync

Enter the Directory and Modify the `xml` Configuration File#

cd  /usr/local/sersync 				# Enter sersync installation directory
cp confxml.xml confxml.xml-bak 		# Backup the original file
vim confxml.xml  					# Edit, modify the following code

Modify several places in the configuration content: relevant information can be seen in your rsync server configuration file /etc/rsyncd.con.
Original configuration file:

# Server IP, file path, and module name settings
<localpath watch="/opt/tongbu">						
# Fill in the path of the folder to be synchronized on the NFS storage server (source server).

<remote ip="127.0.0.1" name="tongbu1"/>				
# Fill in the IP address and module name of the rsync backup server (target server), multiple servers can be configured
<!--<remote ip="192.168.8.39" name="tongbu"/>-->
<!--<remote ip="192.168.8.40" name="tongbu"/>-->
</localpath>

# Authentication section (rsync password authentication)
<rsync>
<auth start="false" users="root" passwordfile="/etc/rsync.pas"/>    
# Enable password authentication, configure auth users + password file path, rsync backup server's authentication information.
</rsync>

# Modify the location of the synchronization failure log, and re-synchronize the failed log every 60 minutes (optional configuration, not required)
<failLog path="/tmp/rsync_fail_log.sh" timeToExecute="60"/><!--default every 60mins execute once-->

Modified configuration file:

<sersync>
	<localpath watch="/www">
	    <remote ip="172.16.12.141" name="backup"/>
	</localpath>
	<rsync>
	    <!--<commonParams params="-artuz"/> -->
      <!-- If you need to back up the original file when modifying the original file, you need to add the parameter b suffix: set the suffix for the original file backup, backup-dir: the directory for backing up the original component -->
        <commonParams params="-artucb --suffix=_bak_`date +%Y%m%d%H%M%S --backup-dir=`date +%Y%m%d`"/>
	    <auth start="true" users="rsync_backup" passwordfile="/etc/rsync.password"/>
	    <userDefinedPort start="false" port="874"/><!-- port=874 -->
	    <timeout start="false" time="100"/><!-- timeout=100 -->
	    <ssh start="false"/>
	</rsync>
	<failLog path="/var/log/rsync_fail_log.sh" timeToExecute="60"/><!--default every 60mins execute once-->

Note: If you need to retain files deleted on the source side on the server side, you need to modify the following configuration.

<inotify>
        <!--<delete start="true"/>    Change true to false-->
        <delete start="false"/>
        <createFolder start="true"/>
        <createFile start="false"/>
        <closeWrite start="true"/>
        <moveFrom start="true"/>
        <moveTo start="true"/>
        <attrib start="false"/>
        <modify start="false"/>
    </inotify>

Start the `sersync` Daemon to Synchronize Data and Test the Program#

Start the `sersync` Daemon#

/usr/local/sersync/sersync2  -d -r -o /usr/local/sersync/confxml.xml

`sersync` Parameter Usage#

-d ： Enable daemon mode
-r ： Before monitoring, push the monitored directory to the remote host using the rsync command
-n ： Specify the number of daemon threads to start, default is 10
-o ： Specify the configuration file, default uses confxml.xml

Successful Start, If Not, It Hangs#

[root@localhost sersync]# /usr/local/sersync/sersync2  -d -r -o /usr/local/sersync/confxml.xml 
set the system param
execute：echo 50000000 > /proc/sys/fs/inotify/max_user_watches
execute：echo 327679 > /proc/sys/fs/inotify/max_queued_events
parse the command param
option: -d 	run as a daemon
option: -r 	rsync all the local files to the remote servers before the sersync work
option: -o 	config xml name：  /usr/local/sersync/confxml.xml
daemon thread num: 10
parse xml config file
host ip : localhost	host port: 8008
will ignore the inotify delete event
daemon start，sersync run behind the console 
use rsync password-file :
user is	rsync_backup
passwordfile is 	/etc/rsync.password
config xml parse success
please set /etc/rsyncd.conf max connections=0 Manually
sersync working thread 12  = 1(primary thread) + 1(fail retry thread) + 10(daemon sub threads) 
Max threads numbers is: 22 = 12(Thread pool nums) + 10(Sub threads)
please according your cpu ，use -n param to adjust the cpu rate
------------------------------------------
rsync the directory recursivly to the remote servers once
working please wait...
execute command: cd /root/rsync_test/log && rsync -artuzb --suffix=._bak_`date +%Y%m%d%H%M%S` --backup-dir=`date +%Y%m%d` -R  ./ [email protected]::log_backup --password-file=/etc/rsync.password >/dev/null 2>&1 
run the sersync: 
watch path is: /root/rsync_test/log

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