Unable to access mail: Warning: Inotify instance limit for user exceeded

Symptoms

• Webmail is not accessible:

  500 external Server Error

• Mailboxes may not be accessible and the following error is shown in the /var/log/maillog file:

  mail16 dovecot: service=imap, user=johndoe@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

• Repairing web configuration finishes with error:

  # 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 restart finishes successfully, but the following notification is shown:

  # service httpd restart

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

• There is sufficient disk space and inodes on the server, what can be checked by executing the commands below:

  # df -h

  OR

  # df -i

• OSSEC IDS is installed on the server.

• Apache restart fails:

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

Cause

Inotify subsystem limits are exceeded. Possibly, by the intrusion detection system.

Resolution

Note: if you do not have a root access to Plesk via SSH, contact your hosting provider regarding the issue.

1. Login to Plesk server via SSH

2. Increase limit for fs.inotify.max_user_watches and fs.inotify.max_user_instances kernel parameters in the /etc/sysctl.conf file:

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

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

3. Apply the changes:

   # sysctl -p