inotify

LinuxTools

Real-time Data Synchronization

In production, there is a need to back up data to a backup server when the file data in the directory changes. The realization of such requirements requires the following two points:

  • Use the monitoring service (inotify) to monitor changes to the directory files of the server to be synchronized
    When the directory data is changed.
  • Use the rsync service to send the data to the backup server. Therefore, real-time data synchronization can be achieved by using rsync + inotify.

Install

Note: you can installl from yum now,
https://github.com/inotify-tools/inotify-tools/wiki

Install from Source

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# Check core version, must latter than 2.6.13
uname -r

# Check and Install the Compile Tools
rpm -qa | grep gcc
rpm -qa | grep make
# Or
yum list installed gcc 
yum list installed make
# Or
yum install gcc make

# Get Source Code and Install
wget -c https://github.com/rvoicilas/inotify-tools/archive/3.20.1.tar.gz

tar xvzf 3.20.1.tar.gz 

./configure && make && make install

Install from Repo(More Convenient Way)

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yum install -y inotify-tools

Example and Explanation of inotifywait

Example

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inotifywait -mrq  /tmp/test --timefmt "%d-%m-%y %H:%M" --format "%T %w%f EVENT: %e" -e create

inotifywait -mrq  /tmp/test --timefmt "%d-%m-%y %H:%M" --format "%T %w%f EVENT: %e" -e delete

inotifywait -mrq  /tmp/test --timefmt "%d-%m-%y %H:%M" --format "%T %w%f EVENT: %e" -e close_write

inotifywait -mrq  /tmp/test --timefmt "%d-%m-%y %H:%M" --format "%T %w%f EVENT: %e" -e move

inotifywait -mrq  /tmp/test --timefmt "%d-%m-%y %H:%M" --format '[%T]%w%f[%e]' -e create,close_write,delete,move

Explanation

Options

-m, –monitor

Instead of exiting after receiving a single event, execute indefinitely. The default behaviour is to exit after the first event occurs.

-d, –daemon

Same as –monitor, except run in the background logging events to a file that must be specified by –outfile. Implies –syslog.

-r, –recursive

Watch all subdirectories of any directories passed as arguments. Watches will be set up recursively to an unlimited depth. Symbolic links are not traversed. Newly created subdirectories will also be watched.

-q, –quiet

If specified once, the program will be less verbose. Specifically, it will not state when it has completed establishing all inotify watches.

–format \<fmt>

Output in a user-specified format, using printf-like syntax. The event strings output are limited to around 4000 characters and will be truncated to this length. The following conversions are supported:

  • %w - This will be replaced with the name of the Watched file on which an event occurred.
  • %f - When an event occurs within a directory, this will be replaced with the name of the File which caused the event to occur. Otherwise, this will be replaced with an empty string.
  • %e - Replaced with the Event(s) which occurred, comma-separated.
  • %Xe - Replaced with the Event(s) which occurred, separated by whichever character is in the place of ‘X’.
  • %T - Replaced with the current Time in the format specified by the –timefmt option, which should be a format string suitable for passing to strftime(3).

Events

move

A file or directory was moved from or to a watched directory. Note that this is actually implemented simply by listening for both moved_to and moved_from, hence all close events received will be output as one or both of these, not MOVE.

Complete Shell Script

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#!/bin/bash
Path=/home/zac/inotify-test

/usr/bin/inotifywait -mrq --timefmt "%d-%m-%y %H:%M" --format '[%T]%w%f[%e]' -e create,close_write,delete,move $Path  | while read -r line
do
	if [ "$line" ];then
		echo "${line}"
		rsync -avzp --password-file="/home/zac/rsync_pass" --log-file="/var/log/rsync" --exclude "/code/config.php" /aemg/cloudclassroom/moodle zac@192.168.1.6::moodle --delete
		rsync -azvp --password-file="/home/zac/rsync_pass" --log-file="/var/log/rsync" --exclude "/code/config.php" /aemg/cloudclassroom/moodle zac@192.168.1.23::moodle --delete
	fi
done

Useful Sites

GitHub Repo wiki of inotify-tools

https://github.com/inotify-tools/inotify-tools/wiki

inofitywait Introduction

https://linux.die.net/man/1/inotifywait

A Tool for Syntax Check of Shell

https://www.shellcheck.net/