[core:emerg] [pid 2013449:tid 140639997298560] (28)No space left on device: AH00023: Couldn't create the proxy mutex
[proxy:crit] [pid 2013449:tid 140639997298560] (28)No space left on device: AH02478: failed to create proxy mutex

In most cases this error message will not allow you to start apache, solution is to restart the server or use the command bellow.

Solution:

ipcs -s | awk -v user=nobody '$3==user {system("ipcrm -s "$2)}'

First

Ensure and check that you've wildcard DNS added to your current DNS hosting provider or in CWP DNS if you're using your own nameservers :

example DNS entry:-

*.domain.tld. 14400 IN A 192.168.1.100

Second

Go to CWP-admin dashboard >> Webserver Settings >> Webservers Domain Settings

there you need to choose the user and then the domain name where you need to set the wildcard subdomain support.

Third

Click on the button "Create configuration" which is located next to the domain name for which you need to enable the wildcard subdomain

Fourth

Choose "Nginx + Php-fpm" or "apache + php-fpm" or "nginx + apache + php-fpm" or "nginx + apache + php-cgi" according to your choice of engines.

If you've chosen "nginx + php-fpm" select the "wildcard" template under "Nginx default vhost template" and save the changes by click on rebuild vhost option.

If "apache + php-fpm" is chosen select "wildcard" template under "Apache default vhost template" and save the changes by click on rebuild vhost option.

If "nginx + apache + php-fpm" or "nginx + apache + php-cgi" is chosen select the "wildcard" template under "Nginx default vhost template" also select "wildcard" template under "Apache default vhost template" and save the changes by click on rebuild vhost option.

That's it you've easily enabled wildcard subdomain support for your domain

**SAME CAN BE DONE FOR SUB-DOMAIN

403 Forbidden
- Mod Security (most common): click here for instructions
- Incorrect include file location
- Other apache rules or permissions
For more details please check apache logs.

500 Internal Server Error
Issue related to the server configuration, examples, and most common issues:
- Domain has custom PHP version configured using .htaccess and that PHP version isn't installed
- Domain has defined Options in .htaccess file, you need to remove line starting with Options
- PHP/PHP-FPM version is not working well with the site code, try another version.
- Error: "End of script output before headers" this can be related to file permissions, try using fix account permissions

502 Bad Gateway
- PHP-FPM is down, try to restart PHP-FPM service
- It can be also related to the small number of php-fpm processes, this can be changed from WebServers_conf by using "PHP-FPM default template" default process limit is 4.
if some have issue increase to 20 or more depending on the requirements
- It can be also related to apache having all processes used if you use nginx, in this case, if the server is not overloaded apache number of the process will need to be increased.

503 Service Unavailable
- This is probably related to incorrect port redirection or php-fpm socket if not working
- php-fpm is down
- php-fpm specific version not installed (example missing php-fpm56 and domain is set to use it)
Error_Log: FCGI: attempt to connect to Unix domain socket /opt/alt/php-fpm56/usr/var/sockets/wwwener.sock (*) failed

Rebuild webservers and tail log: /var/log/cwp/webservers.log
2018-12-20 01:12:57 PHP-FPM php-fpm72: ERROR failed at quota or security limits
TEST

# su USERNAME -c "touch /home/USERNAME/.quota-check" -s /bin/bash
su: cannot create child process: Resource temporarily unavailable
su: cannot open session: System error

then this is probably related to users security limits you need to increase it and don't use 0 as this is the lowest limit.

if we have this output

touch: cannot touch '/home/USERNAME/.quota-check': Permission denied

then this means users home folder has incorrect permissions /home/USERNAME/

it can be also related to session restrictions in the pam file
/etc/pam.d/su [know platforms having this issue: lxckvm]
change "session include system-auth" to "session optional system-auth"

503 Backend fetch failed
- This is probably related to incorrect backend configuration for varnish

https://stackoverflow.com/questions/34548690/how-to-increase-timeout-between-varnish-4-and-nginx

504 GATEWAY TIMEOUT
- probably related to apache or php-fpm not responding, try restarting apache or php-fpm version you are using

For Apache issue: If the issue repeats then try to increase apache limits
For PHP-FPM: If the issue repeats then try to increase the process limit as described above
...more info to be added here

First we always recommend to go with CWP pro as its comes with many premium features like php-fpm which can drastically increase your website's performance and security.

PHP :

In php-fpm we've varieties of cache extension added like :

• Opcache
• APCu
• Redis Object Cache
• Memcached Object cache

this extensions can boost your website even by 30%-70%

we'll learn more about it in below Points :

Opcache :

OPcache improves PHP performance by storing precompiled script bytecode in shared memory, thereby removing the need for PHP to load and parse scripts on each request. i.e. in simple language it can be explained that opcache will help to lower the cpu load by caching some of the already executed php code which drastically lower the cpu load and increase website performance. This is by default enabled with CWP PHP-FPM

APCu :

This is something like php opcache but with more aggressive caching which will help your website to cope with high traffic situations, since it is recommended to use with caution and with supported plugins/modules.

Redis Object cache :

Redis is a persistent object cache backend cache server, this will mainly boost the DB and other website related calls and queries by cache them in to RAM memory (RAM is the fastest memory till date even faster than NVMe and UFS), so take the advantage of redis cache.

to use redis you need to check your website CMS is supporting it or not some CMS have inbuilt support and some needs external plugin to get it enabled like for WORDPRESS you need to use some "Redis Object Cache" or "W3 Total Cache" plugin to get it enabled.

when this is equipped with php inbuilt OPCACHE you can see significant performance improvement.

Memcached Object Cache :
This is also in memory (RAM) object cache but only focused on alleviating database load and good for dynamic websites i.e. it only caches the DB related queries and we didn't recommend to use this with any other cache like redis or APCu. You can use it with php opcache.

to use memcache please check your Script documentation upon how you can do it, For wordpress you can follow this tutorial :

1. Install php memcache (not memcached) from CWP php modules

2. Copy object-cache.php to wp-content - download from here : https://raw.githubusercontent.com/Automattic/wp-memcached/master/object-cache.php

3. Add the `WP_CACHE_KEY_SALT` constant to the `wp-config.php`:

define( 'WP_CACHE_KEY_SALT', '...long random string...' );

This helps prevent cache pollution when multiple WordPress installs are using the same Memcached server. The value must be unique for each WordPress install.

Testing memcache from the command line

watch -td '(echo stats ; echo quit) | nc 127.0.0.1 11211 | grep get*'

You can clean the cache by restarting memcached

service memcached restart

Webserver :

Also you can use nginx + php-fpm as we have some commonly used script template available which will make your site even faster with nginx which is famous for its security and performance benefit. Although nginx can be only used when you're using with your personal website for hosting environment we always recommend Apache as the main webserver you can still use nginx + Apache for performance benefits.

When using nginx + php-fpm the upper cache frameworks will work too universally with apache and nginx

Varnish web cache : Varnish is useful when you've static website, varnish will drastically improve performance from web-server side by caching resources in RAM but it is not idol if you're using dynamic websites/blogs/eCommerce.

You can use Varnish cache with your WordPress blog in CWP as we've created template for WP, you just need to select varnish wordpress template from webserver domain config and you're ready to rock with varnish.

To install xsendfile module you need to follow this steps :

Install dependencies needed for building the module :

yum install libtool git apr apr-devel apr-util apr-util-devel -y

Compiling/Installing xsendfile with CWP-Apache

cd /usr/local/src
rm -rf mod_xsendfile
git clone https://github.com/nmaier/mod_xsendfile.git
cd mod_xsendfile
/usr/local/apache/bin/apxs -a -i -c mod_xsendfile.c

Usage :
for enabling xsendfile for all php use this in .htaccess :

<IfModule mod_xsendfile.c>
  <Files *.php>
    XSendFile On
    XSendFileAllowAbove On
    SetEnv MOD_X_SENDFILE_ENABLED 1
  </Files>
</IfModule>

This tutorial will guide you on how you can enable WebDAV for your user accounts.

Hardness :Medium
Requirements (main) : php 7.1 and above and Apache webserver

Step 1 :

Download and install composer

curl -sS https://getcomposer.org/installer | php
mv composer.phar /usr/local/bin/composer
chmod 755 /usr/local/bin/composer

Step 2 :

Install SabreDAV- WebDav php based

su -l username -s /bin/bash
cd /home/username/public_html
git clone https://github.com/sabre-io/dav.git
cd dav
/opt/alt/php-fpm71/usr/bin/php /usr/local/bin/composer install
or
"use your own php 7.1 bin path" /usr/local/bin/composer install
mkdir data

**replace "username" with you User account name.

you can use PHP switcher or PHP selector or php-fpm

Now create an index.php file in dav directory

nano index.php

and add this script in it and save:

you can edit it like below to change the desired directory :

$rootDirectory = new DAV\FS\Directory('/home/username/public_html');

Fix the permission :

chmod 755 /home/username/public_html/dav
chmod 644 /home/username/public_html/dav/index.php

Step 3 :

As root user now you need to enable the Apache WebDAV modules and it sub required modules :

mod_alias, 
mod_auth_digest, 
mod_authn_core, 
mod_authn_file,
mod_authz_core, 
mod_authz_user, 
mod_dav, 
mod_dav_fs,
mod_setenvif

got to /usr/local/apache/conf/httpd.conf and uncomment (remove the # from the first line of each required module) and uncomment (remove the # ) Include "conf/extra/httpd-dav.conf" file in httpd.conf

Next you also need to add the Directory directive to the domain/subdomain vhost which you want to activate webdav :

for ssl vhost :

   <Directory "/home/username/public_html/dav">
		AllowOverride All
		SSLRequireSSL
		Require all granted
   </Directory>

for non ssl vhost :

	<Directory "/home/username/public_html/dav">
		AllowOverride All
		Require all granted
	</Directory>

*** ensure you added this in main domain vhost i.e. usually under first one and in tag : <VirtualHost 1.1.1.1:443> </VirtualHost>

after changes restart httpd server :

systemctl restart httpd

Step 4 :

Adding authentication to webdav access

In user DAV domain dir /home/username/public_html/dav create .htaccess add this rules for digest auth and rewrite rule :

RewriteRule (.*) index.php [L]
AuthType Digest
AuthName "dav"
AuthDigestDomain /
AuthUserFile /home/username/.htpasswd
Require user username-dav
Satisfy All

**replace username with user account username
***replace username-dav with the dav user name you created with htdigest command below

And create .htpasswd in /home/username and add the digest auth, you need to use htdigest :

htdigest -c /home/username/.htpasswd dav admin

**replace username with user account username

enter the password when prompted.

eg :
admin:dav:595a268370390fe3e20cfffdd583d610

here :-
username-dav : admin
realm : dav
pass : 595a268370390fe3e20cfffdd583d610

Step 5 :

Accessing webdav via domain

go to https://www.yourdomain.tld/dav or http://www.yourdomain.tld/dav

or you can use command line or webdav client in this eg I'm using cadaver package cli :

cadaver https://www.yourdomain.tld/dav

Copy the default templates and save/create it as timeout tpl and stpl:

cd /usr/local/cwpsrv/htdocs/resources/conf/web_servers/vhosts/httpd/php-fpm/
cp default.stpl timeout.stpl
cp default.tpl timeout.tpl

Now you need to edit the both templates "timeout.tpl" and "timeout.stpl" and add this line:

ProxyTimeout 90

under

<IfModule proxy_fcgi_module>

and save it.

** ProxyTimeout 90 is the limit that allows the script to run for 90 seconds before it gets hit with the timeout threshold.
Increase it according to your needs, please don't use too high numbers to avoid server overloads.

eg :

<IfModule proxy_fcgi_module>
    ProxyTimeout 90
    <FilesMatch \.php$>
        SetHandler "proxy:%backend_fcgi%|fcgi://localhost"
    </FilesMatch>
</IfModule>

Now all you need is to create a custom configuration under webserver domain config and select the template or choose this template as a default in the webserver main config.

More info about the custom templates can be found here.

http://HOSTNAME.COM/~USERNAME/

example:

http://srv1.google.com/~yahoo/

NGINX
When using nginx you can use mod_userdir only with apache port.

http://HOSTNAME.COM:8181/~USERNAME/

example:

http://srv1.google.com:8181/~yahoo/

Replace
- HOSTNAME.COM with your server hostname or main IP
- USERNAME with the username of the user

Port 8181 is an apache port when using nginx.
You will need to open a firewall for port 8181 if you want to allow that access.

INFO
Note that mod_userdir always opens only the main account path:
/home/username/public_html

Know to have issues
rsyslog-8.24.0-34.el7.x86_64

How to check

rpm -qa|grep sysl

rsyslog-8.24.0-34.el7.x86_64

service rsyslog status

Redirecting to /bin/systemctl status rsyslog.service
● rsyslog.service - System Logging Service
   Loaded: loaded (/usr/lib/systemd/system/rsyslog.service; enabled; vendor preset: enabled)
   Active: active (running) since Mon 2019-09-02 17:20:12 EEST; 7h ago
     Docs: man:rsyslogd(8)

http://www.rsyslog.com/doc/

 Main PID: 4619 (rsyslogd)
   CGroup: /system.slice/rsyslog.service
           └─4619 /usr/sbin/rsyslogd -n

Sep 02 12:25:44 my.server.com rsyslogd[20369]: imjournal: journal reloaded... [v8.24.0-34.el7 try http://www.rsyslog.com/e/0 ]
Sep 02 16:16:54 my.server.com rsyslogd[20369]: sd_journal_get_cursor() failed: 'Cannot assign requested address'  [v8.24.0-34.el7]
Sep 02 16:17:19 my.server.com rsyslogd[20369]: imjournal: journal reloaded... [v8.24.0-34.el7 try http://www.rsyslog.com/e/0 ]
Sep 02 16:17:19 my.server.com rsyslogd[20369]: sd_journal_get_cursor() failed: 'Cannot assign requested address'  [v8.24.0-34.el7]
Sep 02 16:17:19 my.server.com rsyslogd[20369]: imjournal: journal reloaded... [v8.24.0-34.el7 try http://www.rsyslog.com/e/0 ]
Sep 02 16:37:16 my.server.com rsyslogd[20369]:  [origin software="rsyslogd" swVersion="8.24.0-34.el7" x-pid="20369" x-info="http://www.rsyslog.com"] exiting on signal 15.

Solution
remove rsyslog and install syslog-ng

yum remove rsyslog
yum install syslog-ng

In addition to this, the extension will also set the HTTPS environment variable to "on" in cases where Flexible SSL is in use. This prevents software such as WordPress from being broken by Flexible SSL.

Install mod-cloudflare:

yum install libtool git apr apr-devel apr-util apr-util-devel -y
cd /usr/local/src
git clone https://github.com/cloudflare/mod_cloudflare.git
cd mod_cloudflare
/usr/local/apache/bin/apxs -a -i -c mod_cloudflare.c

Restart httpd service and confirm that mod_cloudflare has been installed:

service httpd restart && /usr/local/apache/bin/httpd -M|grep cloudflare

More Security :

if you need your site is only available via cloudflare IPs, you need to simply add the following to your Apache/httpd configuration file and all non-Cloudflare traffic will be forbidden with status code 403:

DenyAllButCloudFlare

Clouflare ip ranges can be found here :
ipv4 ranges : https://www.cloudflare.com/ips-v4
ipv6 ranges : https://www.cloudflare.com/ips-v6