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Apache failed to start: (24)Too many open files: Init: Can't open server certificate file

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Alexander Tsmokalyuk
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Plesk for Linux kb: technical ABT: Group B

Applicable to:

  • Plesk for Linux

Symptoms

  • It is not possible to start or restart Apache web server, all websites are down:

    # service httpd start
    Starting httpd: [FAILED]

    Or:

    # systemctl start apache2.service
    Job for apache2.service failed because the control process exited with error code. See "systemctl status apache2.service" and "journalctl -xe" for details.

  • The following error can be found in the /var/log/httpd/error_log file ( /var/log/apache2/error.log in Debian and Ubuntu):

    CONFIG_TEXT: [error] (24)Too many open files: Init: Can't open server certificate file /usr/local/psa/var/certificates/cert8bV9dbI
    'import site' failed; use -v for traceback

    Or:

    CONFIG_TEXT: AH00015: Unable to open logs

  • The following error is shown when trying to start Apache using the strace utility (in Debian and Ubuntu, Apache binary is /usr/sbin/apache2 ):

    # strace -q -vttT -s4096 /usr/sbin/httpd -e debug -k start
    ...
    open("/var/www/vhosts/system/example.com/logs/access_ssl_log", O_WRONLY|O_CREAT|O_APPEND|O_CLOEXEC, 0666) = -1 EMFILE (Too many open files) <0.000011>
    write(408, "[Wed Sep 13 21:27:55.156566 2017] [log_config:error] [pid 22172:tid 140081010858112] (24)Too many open files: AH00649: could not open transfer log file /var/www/vhosts/system/example.com/logs/access_ssl_log.\n", 235) = 235 <0.000034>
    write(2, "AH00015: Unable to open logs\n", 29) = 29 <0.000022>

Cause

The maximum allowed number of file descriptors is not enough for Apache web server.

Resolution

Click on a section to expand

For Systemd OS (RHEL 7-based, Debian 8, Ubuntu 16.04)

  1. Connect to the server via SSH

  2. Set desired open files limit to for both Apache and Nginx, using the following shell utility

    # /usr/local/psa/admin/sbin/websrv_ulimits --set 32768 --no-restart

  3. Restart Apache and nginx services at Plesk > Tools & Settings > Services Management to apply changes.

Another solution is to increase open file limit manually:

  1. Create the directory /lib/systemd/system/httpd.service.d/ directory ( apache2.service.d in Debian and Ubuntu):

    # mkdir /lib/systemd/system/httpd.service.d/

  2. In this directory, create limit_nofile.conf file in it with the following content:

    # cat /lib/systemd/system/httpd.service.d/limit_nofile.conf
    [Service]
    LimitNOFILE=65536

  3. Reload systemd unit files and start Apache (in Debian and Ubuntu, service is called apache2.service ):

    # systemctl daemon-reload
    # systemctl start httpd.service

    Note: If the issue still persists on the Debian-like systems, increase limits through APACHE_ULIMIT_MAX_FILES environment variable as it is described below for SysVinit OSes.

For SysVinit OS (RHEL 6-based, RHEL 5, Debian 7)

  • For Debian and Ubuntu:

    1. Connect to the server via SSH

    2. Put the APACHE_ULIMIT_MAX_FILES='ulimit -n 131072' line into the /etc/apache2/envvars file:

      # grep ULIMIT /etc/apache2/envvars
      APACHE_ULIMIT_MAX_FILES='ulimit -n 131072'

    3. Restart the Apache service:

      # service apache2 restart

  • For RHEL-based operating systems:

    1. Connect to the server via SSH

    2. Comment the following section in the /usr/sbin/apachectl file:

      CONFIG_TEXT: #ULIMIT_MAX_FILES="ulimit -S -n `ulimit -H -n`"
      #-------------------- --------------------
      #|||||||||||||||||||| END CONFIGURATION SECTION ||||||||||||||||||||
      #Set the maximum number of file descriptors allowed per child process.
      #if [ "x$ULIMIT_MAX_FILES" != "x" ] ; then
      #$ULIMIT_MAX_FILES
      #fi

    3. After the commented section, add ulimit -n 131072 line:

      CONFIG_TEXT: ..........
      #$ULIMIT_MAX_FILES
      #fi
      ulimit -n 131072

    4. Add the ulimit -n 131072 line into the /etc/sysconfig/httpd file:

      # grep -i ulimit /etc/sysconfig/httpd
      ulimit -n 131072

    5. Restart the Apache service:

      # service httpd restart

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