Apache Web Sever on Ubuntu

Many Linux distros, including Ubuntu Debian, come with preinstalled Apache HTTP web server. It is also known as HTTPD (HTTP Daemon).

Its configuration file is /etc/apache2/apache2.conf:

$ cat /etc/apache2/apache2.conf

# This is the main Apache server configuration file.  It contains the

# configuration directives that give the server its instructions.

# See http://httpd.apache.org/docs/2.4/ for detailed information about

# the directives and /usr/share/doc/apache2/README.Debian about Debian specific

# hints.

#

#

# Summary of how the Apache 2 configuration works in Debian:

# The Apache 2 web server configuration in Debian is quite different to

# upstream's suggested way to configure the web server. This is because Debian's

# default Apache2 installation attempts to make adding and removing modules,

# virtual hosts, and extra configuration directives as flexible as possible, in

# order to make automating the changes and administering the server as easy as

# possible.

# It is split into several files forming the configuration hierarchy outlined

# below, all located in the /etc/apache2/ directory:

#

#       /etc/apache2/

#       |-- apache2.conf

#       |       `--  ports.conf

#       |-- mods-enabled

#       |       |-- *.load

#       |       `-- *.conf

#       |-- conf-enabled

#       |       `-- *.conf

#       `-- sites-enabled

#               `-- *.conf

#

#

# * apache2.conf is the main configuration file (this file). It puts the pieces

#   together by including all remaining configuration files when starting up the

#   web server.

#

# * ports.conf is always included from the main configuration file. It is

#   supposed to determine listening ports for incoming connections which can be

#   customized anytime.

#

# * Configuration files in the mods-enabled/, conf-enabled/ and sites-enabled/

#   directories contain particular configuration snippets which manage modules,

#   global configuration fragments, or virtual host configurations,

#   respectively.

#

#   They are activated by symlinking available configuration files from their

#   respective *-available/ counterparts. These should be managed by using our

#   helpers a2enmod/a2dismod, a2ensite/a2dissite and a2enconf/a2disconf. See

#   their respective man pages for detailed information.

#

# * The binary is called apache2. Due to the use of environment variables, in

#   the default configuration, apache2 needs to be started/stopped with

#   /etc/init.d/apache2 or apache2ctl. Calling /usr/bin/apache2 directly will not

#   work with the default configuration.

# Global configuration

#

#

# ServerRoot: The top of the directory tree under which the server's

# configuration, error, and log files are kept.

#

# NOTE!  If you intend to place this on an NFS (or otherwise network)

# mounted filesystem then please read the Mutex documentation (available

# at <URL:http://httpd.apache.org/docs/2.4/mod/core.html#mutex>);

# you will save yourself a lot of trouble.

#

# Do NOT add a slash at the end of the directory path.

#

#ServerRoot "/etc/apache2"

#

# The accept serialization lock file MUST BE STORED ON A LOCAL DISK.

#

#Mutex file:${APACHE_LOCK_DIR} default

#

# The directory where shm and other runtime files will be stored.

#

DefaultRuntimeDir ${APACHE_RUN_DIR}

#

# PidFile: The file in which the server should record its process

# identification number when it starts.

# This needs to be set in /etc/apache2/envvars

#

PidFile ${APACHE_PID_FILE}

#

# Timeout: The number of seconds before receives and sends time out.

#

Timeout 300

#

# KeepAlive: Whether or not to allow persistent connections (more than

# one request per connection). Set to "Off" to deactivate.

#

KeepAlive On

#

# MaxKeepAliveRequests: The maximum number of requests to allow

# during a persistent connection. Set to 0 to allow an unlimited amount.

# We recommend you leave this number high, for maximum performance.

#

MaxKeepAliveRequests 100

#

# KeepAliveTimeout: Number of seconds to wait for the next request from the

# same client on the same connection.

#

KeepAliveTimeout 5

# These need to be set in /etc/apache2/envvars

User ${APACHE_RUN_USER}

Group ${APACHE_RUN_GROUP}

#

# HostnameLookups: Log the names of clients or just their IP addresses

# e.g., www.apache.org (on) or 204.62.129.132 (off).

# The default is off because it'd be overall better for the net if people

# had to knowingly turn this feature on, since enabling it means that

# each client request will result in AT LEAST one lookup request to the

# nameserver.

#

HostnameLookups Off

# ErrorLog: The location of the error log file.

# If you do not specify an ErrorLog directive within a <VirtualHost>

# container, error messages relating to that virtual host will be

# logged here.  If you *do* define an error logfile for a <VirtualHost>

# container, that host's errors will be logged there and not here.

#

ErrorLog ${APACHE_LOG_DIR}/error.log

#

# LogLevel: Control the severity of messages logged to the error_log.

# Available values: trace8, ..., trace1, debug, info, notice, warn,

# error, crit, alert, emerg.

# It is also possible to configure the log level for particular modules, e.g.

# "LogLevel info ssl:warn"

#

LogLevel warn

# Include module configuration:

IncludeOptional mods-enabled/*.load

IncludeOptional mods-enabled/*.conf

# Include list of ports to listen on

Include ports.conf

# Sets the default security model of the Apache2 HTTPD server. It does

# not allow access to the root filesystem outside of /usr/share and /var/www.

# The former is used by web applications packaged in Debian,

# the latter may be used for local directories served by the web server. If

# your system is serving content from a sub-directory in /srv you must allow

# access here, or in any related virtual host.

<Directory />

        Options FollowSymLinks

        AllowOverride None

        Require all denied

</Directory>

<Directory /usr/share>

        AllowOverride None

        Require all granted

</Directory>

<Directory /var/www/>

        Options Indexes FollowSymLinks

        AllowOverride None

        Require all granted

</Directory>

#<Directory /srv/>

#       Options Indexes FollowSymLinks

#       AllowOverride None

#       Require all granted

#</Directory>

# AccessFileName: The name of the file to look for in each directory

# for additional configuration directives.  See also the AllowOverride

# directive.

#

AccessFileName .htaccess

#

# The following lines prevent .htaccess and .htpasswd files from being

# viewed by Web clients.

#

<FilesMatch "^\.ht">

        Require all denied

</FilesMatch>

#

# The following directives define some format nicknames for use with

# a CustomLog directive.

#

# These deviate from the Common Log Format definitions in that they use %O

# (the actual bytes sent including headers) instead of %b (the size of the

# requested file), because the latter makes it impossible to detect partial

# requests.

#

# Note that the use of %{X-Forwarded-For}i instead of %h is not recommended.

# Use mod_remoteip instead.

#

LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined

LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined

LogFormat "%h %l %u %t \"%r\" %>s %O" common

LogFormat "%{Referer}i -> %U" referer

LogFormat "%{User-agent}i" agent

# Include of directories ignores editors' and dpkg's backup files,

# see README.Debian for details.

# Include generic snippets of statements

IncludeOptional conf-enabled/*.conf

# Include the virtual host configurations:

IncludeOptional sites-enabled/*.conf

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet

Let's try to find the index page of the default web site. From the config file above, we can see where to look for website content:

$ ls /etc/apache2/sites-

sites-available/ sites-enabled/   

$ ls /etc/apache2/sites-available/

000-default.conf  default-ssl.conf

$ ls /etc/apache2/sites-enabled/

000-default.conf

$ cat /etc/apache2/sites-enabled/000-default.conf 

<VirtualHost *:80>

        # The ServerName directive sets the request scheme, hostname and port that

        # the server uses to identify itself. This is used when creating

        # redirection URLs. In the context of virtual hosts, the ServerName

        # specifies what hostname must appear in the request's Host: header to

        # match this virtual host. For the default virtual host (this file) this

        # value is not decisive as it is used as a last resort host regardless.

        # However, you must set it for any further virtual host explicitly.

        #ServerName www.example.com

        ServerAdmin webmaster@localhost

        DocumentRoot /var/www/html

        # Available loglevels: trace8, ..., trace1, debug, info, notice, warn,

        # error, crit, alert, emerg.

        # It is also possible to configure the loglevel for particular

        # modules, e.g.

        #LogLevel info ssl:warn

        ErrorLog ${APACHE_LOG_DIR}/error.log

        CustomLog ${APACHE_LOG_DIR}/access.log combined

        # For most configuration files from conf-available/, which are

        # enabled or disabled at a global level, it is possible to

        # include a line for only one particular virtual host. For example the

        # following line enables the CGI configuration for this host only

        # after it has been globally disabled with "a2disconf".

        #Include conf-available/serve-cgi-bin.conf

</VirtualHost>

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet

And now we can see where is index.html:

$ ls /var/www/html/

index.html

We can see the content of the index.html if we type in /var/www/html/index.html or http://localhost in the browser:

To check which processes are currently listening on which ports:

$ sudo lsof -i -P -n | grep LISTEN

...

apache2    1456                   root    4u  IPv6  31674      0t0  TCP *:80 (LISTEN)

apache2   10763        www-data    4u  IPv6  31674      0t0  TCP *:80 (LISTEN)

apache2   10764        www-data    4u  IPv6  31674      0t0  TCP *:80 (LISTEN)

apache2   10765        www-data    4u  IPv6  31674      0t0  TCP *:80 (LISTEN)

apache2   10766        www-data    4u  IPv6  31674      0t0  TCP *:80 (LISTEN)

apache2   10767        www-data    4u  IPv6  31674      0t0  TCP *:80 (LISTEN)

...

To check if Apache2 service is running:

$ sudo systemctl status apache2

[sudo] password for xxx: 

● apache2.service - The Apache HTTP Server

   Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)

  Drop-In: /lib/systemd/system/apache2.service.d

           └─apache2-systemd.conf

   Active: active (running) since Fri 2020-09-25 10:49:52 BST; 6 days ago

  Process: 4039 ExecReload=/usr/sbin/apachectl graceful (code=exited, status=0/SUCCESS)

 Main PID: 1456 (apache2)

    Tasks: 6 (limit: 4915)

   CGroup: /system.slice/apache2.service

           ├─1456 /usr/sbin/apache2 -k start

           ├─4043 /usr/sbin/apache2 -k start

           ├─4044 /usr/sbin/apache2 -k start

           ├─4045 /usr/sbin/apache2 -k start

           ├─4046 /usr/sbin/apache2 -k start

           └─4047 /usr/sbin/apache2 -k start

Sep 29 07:08:29 bobox systemd[1]: Reloaded The Apache HTTP Server.

Sep 30 00:08:52 bobox systemd[1]: Reloading The Apache HTTP Server.

Sep 30 00:08:52 bobox apachectl[17514]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the '

Sep 30 00:08:52 bobox systemd[1]: Reloaded The Apache HTTP Server.

Oct 01 00:06:42 bobox systemd[1]: Reloading The Apache HTTP Server.

Oct 01 00:06:42 bobox apachectl[12396]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the '

Oct 01 00:06:42 bobox systemd[1]: Reloaded The Apache HTTP Server.

Oct 02 00:06:29 bobox systemd[1]: Reloading The Apache HTTP Server.

Oct 02 00:06:29 bobox apachectl[4039]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'S

Oct 02 00:06:29 bobox systemd[1]: Reloaded The Apache HTTP Server.

How to check if Apache service is enabled at boot time?

$ sudo systemctl is-enabled apache2

enabled

How to disable Apache service at boot time:

$ sudo systemctl disable apache2

Synchronizing state of apache2.service with SysV service script with /lib/systemd/systemd-sysv-install.

Executing: /lib/systemd/systemd-sysv-install disable apache2

The previous command does not stop the service which is already running:

$ sudo lsof -i -P -n | grep LISTEN

...

apache2    1456            root    4u  IPv6   31674      0t0  TCP *:80 (LISTEN)

apache2    4043        www-data    4u  IPv6   31674      0t0  TCP *:80 (LISTEN)

apache2    4044        www-data    4u  IPv6   31674      0t0  TCP *:80 (LISTEN)

apache2    4045        www-data    4u  IPv6   31674      0t0  TCP *:80 (LISTEN)

apache2    4046        www-data    4u  IPv6   31674      0t0  TCP *:80 (LISTEN)

apache2    4047        www-data    4u  IPv6   31674      0t0  TCP *:80 (LISTEN)

...

To stop currently running Apache service:

$ sudo systemctl stop apache2

To verify that the service is stopped:

$ sudo systemctl status apache2

● apache2.service - The Apache HTTP Server

   Loaded: loaded (/lib/systemd/system/apache2.service; disabled; vendor preset: enabled)

  Drop-In: /lib/systemd/system/apache2.service.d

           └─apache2-systemd.conf

   Active: inactive (dead)

Sep 30 00:08:52 bobox systemd[1]: Reloaded The Apache HTTP Server.

Oct 01 00:06:42 bobox systemd[1]: Reloading The Apache HTTP Server.

Oct 01 00:06:42 bobox apachectl[12396]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the '

Oct 01 00:06:42 bobox systemd[1]: Reloaded The Apache HTTP Server.

Oct 02 00:06:29 bobox systemd[1]: Reloading The Apache HTTP Server.

Oct 02 00:06:29 bobox apachectl[4039]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'S

Oct 02 00:06:29 bobox systemd[1]: Reloaded The Apache HTTP Server.

Oct 02 04:36:27 bobox systemd[1]: Stopping The Apache HTTP Server...

Oct 02 04:36:27 bobox apachectl[26754]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the '

Oct 02 04:36:27 bobox systemd[1]: Stopped The Apache HTTP Server.

We can also verify that it's not listening on any ports:

$ sudo lsof -i -P -n | grep LISTEN

// shows no apache2 entries