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

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Marc López
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Plesk for Linux kb: technical ABT: Group A

Applicable to:

  • Plesk for Linux

Symptoms

  • Webmail is not accessible:

    CONFIG_TEXT: 500 Internal Server Error

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

    CONFIG_TEXT: 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

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

  3. Apply the changes:

    # sysctl -p

Comments

5 comments

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  • Avatar
    Stéphan Schamp

    Could this not be fixed by using Dovecot as MDA (Mail Delivery Agent) for Postfix?

    https://workaround.org/ispmail/jessie/postfix-dovecot

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  • Avatar
    Alisa Kasyanova

    @Stéphan Schamp
    The root cause of the issue is not an MDA related, but an OS related one, so using Dovecot is not a workaround for it.

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  • Avatar
    Stéphan Schamp

    @Alisa Kasyanova

    I was thinking about not having to deal with inotify watchers in the first place, as I believe dovecot now is using inotfy watchers to monitor the inboxes for new mails (dropped there by Postfix).
    But Postfix can tell Dovecot (over unix sockets) that there is a new mail, which is a much more logical approach.
    Thus removing the need for these inotify watchers.

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  • Avatar
    Ivan Postnikov (Edited )

    Hello @Stéphan Schamp,

    My apologies for the late response.

    The support request was created to check this suggestion deeper.

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  • Avatar
    Pavel Rozental

    Hello @Stéphan,

    Yes, LMTP can avoid this issue, but LDA  is much easier to be implemented with Postfix and Qmail.

    I have created a request on uservoice to consider replacement Dovecot LDA with Dovecot LMTP.

    Please vote for this feature at https://plesk.uservoice.com/forums/184549-feature-suggestions/suggestions/36135496-implement-dovecot-lmtp

    and provide your vision of the issue. 

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