Can't access mail: Warning: Inotify instance limit for user exceeded

Symptoms

• Webmail is not accessible

  500 Internal Server Error

• The following error is logged to /var/log/maillog

  mail16 dovecot: service=imap, user=jdoe@example.com, ip=[203.0.113.2]. Warning: Inotify instance limit for user (UID popuser) exceeded, disabling. Increase /proc/sys/fs/inotify/max_user_instances

• There are errors while repairing the web configuration

  # plesk repair web
  Repairing server-wide configuration parameters for web servers .. ERR [util_exec] proc_close() failed ['/usr/local/psa/admin/bin/httpdmng' '--reconfigure-server'] with exit code [1]
  [FAILED]
  - httpdmng failed: ERR [util_exec]
  proc_close() failed ['/usr/local/psa/admin/bin/nginx_control' '--restart'] with exit code [1]
  Can not reload proxy server:
  Updating the file of sharing passwords and permissions of users

• Apache fails to start, or displays an error after restarting

  # service apache2 restart
  Failed to add /run/systemd/ask-password to directory watch: inotify watch limit reached

  # service httpd restart
  Redirecting to /bin/systemctl restart httpd.service
  Error: No space left on device

• There's enough space and inodes available, as checked with the commands df -h and df -i

• OSSEC IDS is installed on the server.

Cause

The inotify subsystem limits have been reached, possibly by the intrusion detection system.

Resolution

Note: Contact the hosting provider for assistance if SSH root access is not available.

1. Login to Plesk server via SSH

2. Increase the limit for the following kernel parameters in /etc/sysctl.conf:

   Note: If Plesk runs on a virtual container, the kernel parameter should be increased on the hardware node

   fs.inotify.max_user_watches = 560144
   fs.inotify.max_user_instances = 512

3. Apply the changes:

   # sysctl -p