Thursday, 5 November 2020

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

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