Starting Apache as service quits with SIGWINCH

Question

When running service apache start I see in the log file this entry:

[mpm_event:notice] [pid 1906:tid XXX] AH00489: Apache/2.4.23 (Unix)
                         OpenSSL/1.0.2g PHP/7.0.9 configured -- resuming normal operations
[core:notice] [pid 1906:tid XXX] AH00094: Command line: '/usr/sbin/httpd'
[mpm_event:notice] [pid 1906:tid XXX] AH00492: caught SIGWINCH, shutting down gracefully

and the service apache does not start? I can find in internet what SIGWINCH means [Window size change] but it does not really help me in this case.

The file /etc/systemd/system/apache.service:

[Unit]
Description=The Apache Webserver [FaF Compiled]
After=network.target nss-lookup.target time-sync.target
Before=getty@tty1.service plymouth-quit.service xdm.service

[Service]
Type=notify
PrivateTmp=true
ExecStart=/usr/sbin/httpd -k start
ExecReload=/usr/sbin/httpd -k graceful
ExecStop=/usr/sbin/httpd -k graceful-stop
KillMode=mixed

[Install]
WantedBy=multi-user.target
Alias=httpd.service apache.service

Running on SLES 12 SP1. I have compiled Apache on my own. Starting it with apachectl -k start works perfectly and I can access and run the PHP code.

My question: What am I doing wrong that the apache service does not start. I have enabled it with systemctl enable apache. This was the output:

ln -s '/usr/lib/systemd/system/apache2.service' '/etc/systemd/system/httpd.service'
ln -s '/usr/lib/systemd/system/apache2.service' '/etc/systemd/system/apache.service'
ln -s '/usr/lib/systemd/system/apache2.service' '/etc/systemd/system/multi-user.target.wants/apache2.service'

Answer 1

systemd is instructing Apache to stop with graceful-stop, which generates a SIGWINCH signal, and hence the log caught SIGWINCH, shutting down gracefully. (the SIGWINCH signal is (ab)used by Apache)

IMO, there is a possibility of another error, including configuration errors, making it stop, and you are looking at related symptoms which are normal behaviour.

I would recommend perusing your Apache error logs, usually by default in SLES under the directory /var/log/apache2.

Answer 2

I found a similar problem reported on RedHat. Closed with a status "NOTABUG". Eventually recognised as wrong config.

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UPDATE

I found one more similar problem reported on serverfault. And one more in the answer to it, in the image below.

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Answer 3

From a comment on the Red Hat bug report linked from Tomasz's answer:

It looks like you need to run 00-systemd.conf if you want systemd to recognize that httpd has started successfully.

I ran this and it worked:

ln -sr /etc/httpd/conf.modules.d/00-systemd.conf /etc/httpd/conf.d/00-systemd.conf
systemctl restart httpd

I'm on Amazon Linux 2 (will probably also work on RHEL/Centos 7).