Prerequisites
- Access to root user or a user with sudo privileges.
- Basic knowledge of working with the Linux command line.
Step 1: Checking Current inotify Watchers Limits
Before setting up monitoring, it's important to check the current inotify watchers limit on your system. Open a terminal and run the following command:
cat /proc/sys/fs/inotify/max_user_watches
This command will display the current inotify watchers limit. The default value might be relatively low, for example, 8192, which could be insufficient for some applications.
Step 2: Increasing inotify Watchers Limits
If you find that the default limit is inadequate, you can increase it. Edit the /etc/sysctl.conf file and add the following line:
fs.inotify.max_user_watches=524288
After adding the line, save the file and apply the changes using the command:
sudo sysctl -p
Step 3: Installing and Configuring inotify Watchers Monitoring Tool
One of the tools you can use for monitoring inotify watchers is inotify-tools. Install it using YUM:
sudo yum install inotify-tools
After installation, you can use inotifywait to monitor file system events in real-time.
Step 4: Setting Up Alert Script
For automatic alerting upon reaching a certain number of used watchers, you can create a script that regularly checks their count and sends alerts via email or a notification system.
Create a file named check_inotify.sh with the following content:
#!/bin/bash
CURRENT=$(cat /proc/sys/fs/inotify/max_user_watches)
THRESHOLD=500000
if [ "$CURRENT" -gt "$THRESHOLD" ]; then
echo "Number of inotify watchers exceeded the limit of $THRESHOLD" | mail -s "Warning: Inotify Limit Exceeded" This email address is being protected from spambots. You need JavaScript enabled to view it.
fi
Make sure to replace This email address is being protected from spambots. You need JavaScript enabled to view it. with the actual email address. Make the script executable:
chmod +x check_inotify.sh
Step 5: Automating the Script Using cron
For regular checking, use cron. Open the crontab for editing:
crontab -e
And add a line to run the script every 10 minutes:
*/10 * * * * /path/to/check_inotify.sh
This way, your CentOS 7 system will monitor and alert on exhaustion of inotify watchers, helping prevent performance issues in applications caused by a lack of available watchers.
