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Linux Internet Web Server and Domain Configuration Tutorial

HowTo Create an Apache based Linux website server

Create a web server with Linux, Apache, FTP and bind DNS: This tutorial covers the Linux server configuration required to host a website. The Apache web server, FTP server and DNS configuration are covered. The Apache web server is required to serve the web pages, the FTP server is required for users to upload content and the DNS server is required to resolve the domain names so that a URL entered into a web browser will point to your web server and properly serve the correct pages. The configurations presented will include virtual hosting which will allow a single Linux server to support multiple web site domains.

Web Site Prerequisites:

This tutorial assumes that a computer has Linux installed and running. See RedHat Installation for the basics. A connection to the internet is also assumed. A connection of 128 Mbits/sec or greater will yield the best results. ISDN, DSL, cable modem or better are all suitable. A 56k modem will work but the results will be mediocre at best. The tasks must also be performed with the root user login and password.

No single distribution seems to have an advantage. A Ubuntu, SuSe, Fedora, Red Hat or CentOS distribution will include all of the software you will need to configure a web server. If using Red Hat Enterprise Linux, both the Workstation or the Server edition will support your needs except that the Workstation edition will not include the vsFTP package. It will have to be compiled from source or use sftp.

Software Prerequisites: The Apache web server (httpd), FTP (requires xinetd or inetd) and Bind (named) software packages with their dependencies are all required. One can use the rpm command to verify installation:

  • Fedora Core 1+, Red Hat Enterprise 4/5, CentOS 4/5:
       rpm -q httpd bind bind-chroot bind-utils system-config-bind xinetd vsftpd
    RPMs added FC2+: system-config-httpd
    RPMs added FC3+: httpd-suexec

  • Red Hat 9.0
       rpm -q httpd bind xinetd vsftpd
    A Red Hat 8.0 wu-ftpd RPM may be installed (Newer version 2.6.2 or later with security fix wu-ftpd-2.6.2-11) or install from source (rev 14).

  • Red Hat 8.0
       rpm -q httpd bind xinetd wu-ftpd
  • Red Hat 7.x:
       rpm -q apache bind inetd wu-ftpd
    Use wu-ftpd version 2.6.2 or later to avoid security problems.

  • SuSE 9.3:
       rpm -ivh apache2 apache2-prefork bind bind-chrootenv bind-utils vsftpd
    Note: The apache2-MPM is a generic term for Apache installation options for "Multi-Processing Modules (MPM)s "prefork" or "worker". If you try and only install apache2 you will get the following error:
       apache2-MPM is needed by apache2-2.0.53-9
    Also see Apache.org: MPMs

  • Ubuntu (natty 11.04/14.04) / Debian:
       apt-get install apache2
       apt-get install bind9 
       apt-get install vsftpd 

  • Ubuntu (dapper 6.06/hardy 8.04) / Debian:
       apt-get install apache2 apache2-common apache2-mpm-prefork apache2-utils
       apt-get install bind9 
       apt-get install vsftpd 

One should also have a working knowledge of the Linux init process so that these services are initiated upon system boot. See the YoLinux init process tutorial for more info.

Apache HTTP Web server configuration:

The Apache web server configuration file is: /etc/httpd/conf/httpd.conf

Web pages are served from the directory as configured by the DocumentRoot directive. The default directory location is:

Linux distributionApache web server "DocumentRoot"
Red Hat 7.x-9, Fedora Core, Red Hat Enterprise 4/5/6, CentOS 4/5/6 /var/www/html/
Red Hat 6.x and older /home/httpd/html/
Suse 9.x /srv/www/htdocs/
Ubuntu (dapper 6.06) / Debian /var/www/html
Ubuntu (hardy 8.04/natty 11.04/trusty 14.04) / Debian /var/www
The default home page for the default configuration is index.html. Note the pages should not be owned by user apache as this is the process owner of the httpd web server daemon. If the web server process is compromised, it should not be allowed to alter the files. The files should of course be readable by user apache.

Apache may be configured to run as a host for one web site in this fashion or it may be configured to serve for multiple domains. Serving for multiple domains may be achieved in two ways:

  • Virtual hosts: One IP address but multiple domains - "Name based" virtual hosting.
  • Multiple IP based virtual hosts: One IP address for each domain - "IP based" virtual hosting.
The default configuration will allow one to have multiple user accounts under one domain by using a reference to the user account: http://www.domain.com/~user1/. If no domain is registered or configured, the IP address may also be used: http://XXX.XXX.XXX.XXX/~user1/.

[Potential Pitfall] The default umask for directory creation is correct by default but if not use: chmod 755 /home/user1/public_html

[Potential Pitfall] When creating new "Directory" configuration directives, I found that placing them by the existing "Directory" directives to be a bad idea. It would not use the .htaccess file. This was because the statement defining the use of the .htaccess file was after the "Directory" statement. Previously in RH 6.x the files were separated and the order was defined a little different. I now place new "Directory" statements near the end of the file just before the "VirtualHost" statements.

For users of Red Hat 7.1, the GUI configuration tool apacheconf was introduced for the crowd who like to use pretty point and click tools.

Files used by Apache:

  • Start/stop/restart script:
    • Red Hat/Fedora/CentOS: /etc/rc.d/init.d/httpd
    • SuSE 9.3: /etc/init.d/apache2
    • Ubuntu (dapper 6.06/hardy 8.04/natty 11.04/trusty 14.04) / Debian: /etc/init.d/apache2
  • Apache main configuration file:
    • Red Hat/Fedora/CentOS: /etc/httpd/conf/httpd.conf
    • SuSE: /etc/apache2/httpd.conf
      (Need to add directive: ServerName host-name)
    • Ubuntu (dapper 6.06/hardy 8.04/natty 11.04/trusty 14.04) / Debian: /etc/apache2/apache2.conf
  • Apache supplementary configuration files:
    • Red Hat/Fedora/CentOS: /etc/httpd/conf.d/component.conf
    • SuSE: /etc/apache2/conf.d/component.conf
    • Ubuntu (dapper 6.06/hardy 8.04/natty 11.04/trusty 14.04) / Debian:
      • Virtual domains: /etc/apache2/sites-enabled/domain
        (Create soft link from /etc/apache2/sites-enabled/domain to /etc/apache2/sites-available/domain to turn on. Use command a2ensite)
      • Additional configuration directives: /etc/apache2/conf.d/
      • Modules to load: /etc/apache2/mods-available/
        (Soft link to /etc/apache2/mods-enabled/ to turn on)
      • Ports to listen to: /etc/apache2/ports.conf
  • /var/log/httpd/access_log and error_log - Red Hat/Fedora Core Apache log files
    (Suse: /var/log/apache2/)

Start/Stop/Restart scripts: The script is to be run with the qualifiers start, stop, restart or status.
i.e. /etc/rc.d/init.d/httpd restart. A restart allows the web server to start again and read the configuration files to pick up any changes. To have this script invoked upon system boot issue the command chkconfig --add httpd. See Linux Init Process Tutorial for a more complete discussion.

Also Apache control tool: /usr/sbin/apachectl start

Apache Control Command: apachectl:

Red Hat / Fedora Core / CentOS: apachectl directive
Ubuntu dapper 6.06 / hardy 8.04 / natty 11.04 / trusty 14.04 / Debian: apachectl (softlink to apache2ctl) or apache2ctl directive
Directive Description
start Start the Apache httpd daemon. Gives an error if it is already running.
stop Stops the Apache httpd daemon.
graceful Gracefully restarts the Apache httpd daemon. If the daemon is not running, it is started. This differs from a normal restart in that currently open connections are not aborted.
graceful-stop Gracefully stops the Apache httpd daemon. This differs from a normal restart in that currently open connections are not aborted.
restart Restarts the Apache httpd daemon. If the daemon is not running, it is started. This command automatically checks the configuration files as in configtest before initiating the restart to make sure the daemon doesn't die.
status Displays a brief status report.
fullstatus Displays a full status report from mod_status. Requires mod_status enabled on your server and a text-based browser such as lynx available on your system. The URL used to access the status report can be set by editing the STATUSURL variable in the script.
Run a configuration file syntax test.

Apache control tool: apachectl - man page

Apache Configuration Files:

  • /etc/httpd/conf/httpd.conf: is used to configure Apache. In the past it was broken down into three files. These may now be all concatenated into one file. See Apache online documentation for the full manual.
  • /etc/httpd/conf.d/application.conf: All configuration files in this directory are included during Apache start-up. Used to store application specific configurations.
  • /etc/sysconfig/httpd: Holds environment variables used when starting Apache.

Basic settings: Change the default value for ServerName www.<your-domain.com>

Giving Apache access to the file system: It is prudent to limit Apache's view of the file system to only those directories necessary. This is done with the directory statement. Start by denying access to everything, then grant access to the necessary directories.

Deny access completely to file system root ("/") as the default:

Deny first, then grant permissions:
<Directory />
   Options None
   AllowOverride None

Set default location of system web pages and allow access: (Red Hat/Fedora/CentOS)
DocumentRoot "/var/www/html"

<Directory "/var/www/html">
   Options Indexes FollowSymLinks
   AllowOverride None
   Order allow,deny
   Allow from all
   Require all granted   - This is required for Apache 2.4+
Note: The directive "Require all granted" is new as of Apache httpd 2.4.3.
Legacy behavior can be achieved with the command: sudo a2enmod access_compat

Grant access to a user's web directory: public_html

  • Enabling Red Hat / Fedora Linux, Apache public_html user directory access:

    This will allow users to serve content from their home directories under the sub-directory "/home/userid/public_html/" by accessing the URL http://hostname/~userid/

    File: /etc/httpd/conf/httpd.conf
    LoadModule userdir_module modules/mod_userdir.so
    <IfModule mod_userdir.c>
        #UserDir disable             - Add comment to this line
        # To enable requests to /~user/ to serve the user's public_html
        # directory, remove the "UserDir disable" line above, and uncomment
        # the following line instead:
        UserDir public_html          # Un-comment this line
    <Directory /home/*/public_html>
        AllowOverride FileInfo AuthConfig Limit
        Options MultiViews Indexes SymLinksIfOwnerMatch IncludesNoExec
        <Limit GET POST OPTIONS>
            Order allow,deny
            Allow from all
        <LimitExcept GET POST OPTIONS>
            Order deny,allow
            Deny from all
    Change to a comment (add "#" at beginning of line) from Fedora Core default UserDir disable and assign the directory public_html as a web server accessible directory.
    Assign a single user the specific ability to share their directory:
    <Directory /home/user1/public_html>
       Options Indexes Includes FollowSymLinks
       AllowOverride None
       order allow,deny
       allow from all
       Require all granted   - This is required for Apache 2.4+
    Allows the specific user, "user1" only, the ability to serve the directory /home/user1/public_html/

    Also use SELinux command to set the security context: setsebool httpd_enable_homedirs true

    Directory permissions: The Apache web server daemon must be able to read your web pages in order to feed their contents to the network. Use an appropriate umask and file protection. Allow access to web directory: chmod ugo+rx -R public_html.
    Note that the user's directory also has to have the appropriate permissions as it is the parent of public_html.
    Default permissions on user directory: ls -l /home
    drwx------ 20 user1 user1 4096 Mar 5 12:16 user1
    Allow the web server access to operate the parent directory: chmod ugo+x /home/user1
    d-wx--x--x 20 user1 user1 4096 Mar 5 12:16 user1

    One may also use groups to control permissions. See the YoLinux tutorial on managing groups.

  • Enabling Ubuntu's Apache public_html user directory access:

    Ubuntu has broken out the Apache loadable module directives into the directory /etc/apache2/mods-available/. To enable an Apache module, generate soft links to the directory /etc/apache2/sites-enabled/ by using the commands a2enmod/a2dismod to enable/disable Apache modules.

    • [root@node2]# a2enmod
      A list of available modules is displayed. Enter "userdir" as the module to enable.
    • Restart Apache with the following command: /etc/init.d/apache2 force-reload

    Note: This is the same as manually generating the following two soft links:

    • ln -s /etc/apache2/mods-available/userdir.conf /etc/apache2/mods-enabled/userdir.conf
    • ln -s /etc/apache2/mods-available/userdir.load /etc/apache2/mods-enabled/userdir.load
    Man page: a2enmod/a2dismod

    [Potential Pitfall]: If the Apache web server can not access the file you will get the error "403 Forbidden" "You don't have permission to access file-name on this server." Note the default permissions on a user directory when first created with "useradd" are:

    drwx------ 3 userx userx

    You must allow the web server running as user "apache" to access the directory if it is to display pages held there.

    Fix with command: chmod ugo+rx /home/userx

    drwxr-xr-x 3 userx userx

Config File Order Of Operation:

The configuration directives are assigned in the order in which they are read. This is important otherwise unexpected behavior may result.

Red Hat/CentOS/Fedora/AWS configuration files are read in the following order:

  1. /etc/httpd/conf/httpd.conf
    reads include files "Include conf.modules.d/*.conf" and "IncludeOptional conf.d/*.conf"
  2. /etc/httpd/conf.modules/*.conf
  3. /etc/httpd/conf.d/*.conf (typically virtual domain definitions for various web sites)
    The conf files are read in alphabetical order.

Ubuntu/Debian configuration files are read in the following order:

  1. /etc/apache2/apache2.conf
    reads include files
  2. /etc/apache2/mods-enabled/*.load
  3. /etc/apache2/mods-enabled/*.conf
  4. /etc/apache2/conf-enabled/*.conf
  5. /etc/apache2/sites-enabled/*.conf (typically virtual domain definitions for various web sites)
    The conf files are read in alphabetical order.

The server default for access using the IP address is typically the first domain defined in "conf.d/*.conf" as defined by the alphabetical order. This is also the site hackers see when scanning the net via IP addresses. It is often a curse to have a domain starting with the letter "a" as mis-configured servers will lead all hacker traffic to this site. Thus it is good practice to to generate a default configuration for IP address access.

File: /etc/httpd/conf.d/1st.conf (Ubuntu: /etc/apache2/sites-enabled/1st.conf)
DirectoryIndex index.html
<VirtualHost *:80>
    ServerName   www4.defaultdomain.com
    DocumentRoot /srv/www/default/html
    ErrorLog     /var/log/httpd/1st-error.log
    TransferLog  /var/log/httpd/1st-access.log
    <Directory "/">
        Options FollowSymLinks
        AllowOverride None
    <Directory /srv/www/default/html>
        Options FollowSymLinks MultiViews Includes
        IndexOptions SuppressLastModified SuppressDescription
        AllowOverride All
        Order allow,deny
        allow from all
Default web page: /srv/www/default/html/index.html should be a static simple page with no DB or CMS access. After all the only ones who end up here are hackers.

SELinux security contexts:

Fedora Core 3 and Red Hat Enterprise Linux 4 introduced SELinux (Security Enhanced Linux) security policies and context labels.
To view the security context labels applied to your web page files use the command: ls -Z

The system enables/disables SELinux policies in the file /etc/selinux/config
SELinux can be turned off by setting the directive SELINUX. (Then reboot the system):

or using the command setenforce 0 to temporarily disable SELinux until the next reboot.

When using SELinux security features, the security context labels must be added so that Apache can read your files. The default security context label used is inherited from the directory for newly created files. Thus a copy (cp) must be used and not a move (mv) when placing files in the content directory. Move does not create a new file and thus the file does not receive the directory security context label. The context labels used for the default Apache directories can be viewed with the command: ls -Z /var/www
The web directories of users (i.e. public_html) should be set with the appropriate context label (httpd_sys_content_t).

Assign a security context for web pages: chcon -R -h -t httpd_sys_content_t /home/user1/public_html

  • -R: Recursive. Files and directories in current directory and all sub-directories.
  • -h: Affect symbolic links.
  • -t: Specify type of security context.

Use the following security contexts:

Context Type Description
httpd_sys_content_t Used for static web content. i.e. HTML web pages.
httpd_sys_script_exec_t Use for executable CGI scripts or binary executables.
httpd_sys_script_rw_t CGI is allowed to alter/delete files of this context.
httpd_sys_script_ra_t CGI is allowed to read or append files of this context.
httpd_sys_script_ro_t CGI is allowed to read files and directories of this context.

Set the following options: setsebool httpd-option true
(or set to false)

Policy Description
httpd_enable_cgi Allow httpd cgi support.
httpd_enable_homedirs Allow httpd to read home directories.
httpd_ssi_exec Allow httpd to run SSI executables in the same domain as system CGI scripts.
Then restart Apache:
  • Red Hat/Fedora/Suse and all System V init script based Linux systems: /etc/init.d/httpd restart
  • Red Hat/Fedora: service httpd restart

The default SE boolean values are specified in the file: /etc/selinux/targeted/booleans

For more on SELinux see the YoLinux Systems Administration tutorial.

Virtual Hosts:

The Apache web server allows one to configure a single computer to represent multiple websites as if they were on separate hosts. There are two methods available and we describe the configuration of each. Choose one method for your domain:
  • Name based virtual host: (most common) A single computer with a single IP address supporting multiple web domains. The web browser using the http protocol, identifies the domain being addressed.
  • IP based virtual host: The virtual hosts can be configured as a single multi-homed computer with multiple IP addresses on a single network card, with each IP address representing a different web domain. This has the appearance of a web domain supported by a dedicated computer because it has a dedicated IP address.

Configuring a "name based" virtual host:

A virtual host configuration allows one to host multiple web site domains on one server. (This is not required for a dedicated Linux server which hosts a single web site.)

NameVirtualHost XXX.XXX.XXX.XXX

<VirtualHost XXX.XXX.XXX.XXX>
ServerName www.your-domain.com - CNAME (DNS alias www) specified in (/var/named/...) ServerAlias your-domain.com - Allows requests without the "www" prefix. ServerAdmin user1@your-domain.com DocumentRoot /home/user1/public_html
ErrorLog logs/your-domain.com-error_log TransferLog logs/your-domain.com-access_log </VirtualHost>

  • You can specify more than one IP address. i.e. if web server is also being used as a firewall/gateway and you have an external internet IP address as well as a local network IP address.
    NameVirtualHost XXX.XXX.XXX.XXX
    NameVirtualHost 192.168.XXX.XXX
    <VirtualHost XXX.XXX.XXX.XXX 192.168.XXX.XXX>
    See the YoLinux Tutorial on configuring a network gateway/firewall using iptables and NAT.
  • Use your IP address for XXX.XXX.XXX.XXX, actual domain name and e-mail address.
    One can use DNS views to provide different local network DNS results.

  • The host IP address can be referenced generically to operate on all NICs:
    <VirtualHost *:80>
    Note this method is preferred for NAT based hosting like Amazon Web Services (AWS) EC2.

  • Note that I configure Apache for both requests http://www.domain-name.com and http://domain-name.com.

  • Once virtual hosts are configured, your default system domain (/var/www/html) will stop working. Your default domain now must be configured as a virtual domain.
    <Directory "/var/www/html">
       ...  This part remains the same
    # Default for when no domain name is given (i.e. access by IP address)
    <VirtualHost *:80>
       ServerAdmin user1@your-domain.com
       DocumentRoot /var/www/html
       ErrorLog logs/error_log
       TransferLog logs/access_log
    # Add a VirtualHost definition for your domain which was once the system default.
    <VirtualHost XXX.XXX.XXX.XXX>
    ServerName www.your-domain.com ServerAlias your-domain.com ServerAdmin user1@your-domain.com DocumentRoot /var/www/html ErrorLog logs/error_log TransferLog logs/access_log </VirtualHost> ... ..

  • Forwarding to a primary URL. It is best to avoid the appearance of duplicated web content from two URLs such as http://www.your-domain.com and http://your-domain.com. Supply a forwarding Apache "Redirect".
    <VirtualHost XXX.XXX.XXX.XXX>
       ServerName www.your-domain.com   - Note that no aliases are listed
    # Add a VirtualHost definition to forward to your primary URL
    <VirtualHost XXX.XXX.XXX.XXX>
       ServerName your-domain.com
       ServerAlias other-domain.com
       ServerAlias www.other-domain.com
       Redirect permanent / http://www.your-domain.com.com/

  • More virtual host examples.

When specifying more domains, they may all use the same IP address or some/all may use their own unique IP address. Specify a "NameVirtualHost" for each IP address.

After the Apache configuration files have been edited, restart the httpd daemon: /etc/rc.d/init.d/httpd restart (Red Hat) or /etc/init.d/apache2 restart (Ubuntu / Debian)

Apache virtual domain configuration with Ubuntu:

Ubuntu separates out each virtual domain into a separate configuration file held in the directory /etc/apache2/sites-available/. When the site domain is to become active, a soft link is created to the directory /etc/apache2/sites-enabled/.

Example: /etc/apache2/sites-available/supercorp
<VirtualHost XXX.XXX.XXX.XXX>
        ServerName supercorp.com
        ServerAlias www.supercorp.com
        ServerAdmin webmaster@localhost

        DocumentRoot /home/supercorp/public_html/home
        <Directory "/">
                Options FollowSymLinks
                AllowOverride None
        <Directory /home/supercorp/public_html/home>
                Options Indexes FollowSymLinks MultiViews
                IndexOptions SuppressLastModified SuppressDescription
                AllowOverride All
                Order allow,deny
                allow from all
                Require all granted   - This is required for Apache 2.4+

        ScriptAlias /cgi-bin/ /home/supercorp/cgi-bin/
        <Directory "/home/supercorp/cgi-bin/">
                AllowOverride None
                Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
                Order allow,deny
                Allow from all

        ErrorLog /var/log/apache2/supercorp.com-error.log

        # Possible values include: debug, info, notice, warn, error,
        # crit, alert, emerg.
        LogLevel warn
        CustomLog /var/log/apache2/supercorp.com-access.log combined
        ServerSignature On
Enable domain:
  • Create soft link:
    • Manually: ln -s /etc/apache2/sites-available/supercorp /etc/apache2/sites-enabled/supercorp
    • Use Ubuntu scripts a2ensite/a2dissite. Type command and it will prompt you as to which site you would like to enable or disable.
  • Restart Apache:
    • apachectl graceful
    • /etc/init.d/apache2 restart
    • /etc/init.d/apache2 reload
Also note that Apache modules can also be enabled/disabled with scripts a2enmod/a2dismod.

Man pages:

Configuring an "IP based" virtual host:

One may assign multiple IP addresses to a single network interface. See the YoLinux networking tutorial: Network Aliasing. Each IP address may then be it's own virtual server and individual domain. The downside of the "IP based" virtual host method is that you have to possess multiple/extra IP addresses. This usually costs more. The standard name based virtual hosting method above is more popular for this reason.

NameVirtualHost *              - Indicates all IP addresses

<VirtualHost *>
   ServerAdmin user0@default-domain.com
   DocumentRoot /home/user0/public_html

<VirtualHost XXX.XXX.XXX.101>
   ServerAdmin user1@domain-1.com
   DocumentRoot /home/user1/public_html

<VirtualHost XXX.XXX.XXX.102>
   ServerAdmin user1@domain-2.com
   DocumentRoot /home/user2/public_html
The default <VirtualHost *> block will be used as the default for all IP addresses not specified explicitly. This default IP (*) may not work for https URL's.

CGI: (Common Gateway Interface)

CGI is a program executable which dynamically generates a web page by writing to stdout. CGI is permitted by either of two configuration file directives:
  • ScriptAlias:
    • Red Hat 7.x-9, Fedora core: ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"
    • Red Hat 6.x and older: ScriptAlias /cgi-bin/ "/home/httpd/cgi-bin/"
    • Suse 9.x: ScriptAlias /cgi-bin/ "/srv/www/cgi-bin/"
    • Ubuntu (dapper/hardy/natty) / Debian: ScriptAlias /cgi-bin/ "/usr/lib/cgi-bin/"
  • Options +ExecCGI:
    <Directory /var/www/cgi-bin>
    Options +ExecCGI
The executable program files must have execute privileges, executable by the process owner (Red Hat 7+/Fedora Core: apache. Older use nobody) under which the httpd daemon is being run.

Configuring CGI To Run With User Privileges:

The suEXEC feature provides Apache users the ability to run CGI and SSI programs under user IDs different from the user ID of the calling web-server. Normally, when a CGI or SSI program executes, it runs as the same user who is running the web server.
NameVirtualHost XXX.XXX.XXX.XXX

<VirtualHost XXX.XXX.XXX.XXX>
   ServerName node1.your-domain.com                   - Allows requests by domain name without the "www" prefix.
   ServerAlias your-domain.com www.your-domain.com   - CNAME (alias www) specified in Bind configuration file (/var/named/...)
   ServerAdmin user1@your-domain.com
   DocumentRoot /home/user1/public_html/your-domain.com
   ErrorLog logs/your-domain.com-error_log
   TransferLog logs/your-domain.com-access_log

   SuexecUserGroup user1 user1
   <Directory /home/user1/public_html/your-domain.com/>
      Options +ExecCGI +Indexes
      AddHandler cgi-script .cgi

ERROR Pages:

You can specify your own web pages instead of the default Apache error pages:

ErrorDocument 404 /Error404-missing.html
Create the file Error404-missing.html in your "DocumentRoot" directory.

Handle all errors with a forwarding page:

ErrorDocument 400 /error.shtml
ErrorDocument 401 /error.shtml
ErrorDocument 403 /error.shtml
ErrorDocument 404 /error.shtml
ErrorDocument 500 /error.shtml

Sample file error.shtml (in your "DocumentRoot" directory).
<!--#echo var="REQUEST_URI" -->
<!--#echo var="REDIRECT_STATUS" -->
<h2>Page does not found!</h2>
<!-- Redirect to home page -->
<META HTTP-EQUIV="Refresh" Content="1; URL=http://www.megacorp.com/">


If the appropriate php, perl and httpd RPM's are installed, the default Red Hat Apache configuration and modules will support PHP content. RPM Packages (RHEL):

  • php: HTML-embedded scripting language
  • php-pear: PEAR is a framework and distribution system for reusable PHP components.
  • php-mysql: MySQL database support.
  • php-ldap: Lightweight Directory Access Protocol (LDAP) support

Apache configuration:

Add php default page index.php to apache config file: /etc/httpd/conf/httpd.conf

DirectoryIndex index.html index.htm index.php

PHP Configuration File:
  • AWS - PHP 5.6: /etc/php-5.6.d/php.ini
  • RHEL4 - PHP 4.3: /etc/php.ini
  • Ubuntu 18.04: /etc/php/7.2/apache2/php.ini
  • Ubuntu 6.06/6.11: /etc/php5/apache2/php.ini
engine = On
display_errors = Off
include_path = ".:/php/includes"
memory_limit = 32M   ; Default is typically 8MB which is too low.

mysql.default_host = superserver    ; Hostname of the computer
mysql.default_user = dbuser
Small portion of file shown.
Note that changes will not take effect until the apache web server daemon is restarted.

Test you PHP capabilities with this test file: /home/user1/public_html/test.php

OR (older format)
Test: http://localhost/~user1/test.php

For more info see YoLinux list of PHP information web sites.

Running Multiple instances of httpd:

The Apache web server daemon (httpd) can be started with the command line option "-f" to specify a unique configuration file for each instance. Configure a unique IP address for each instance of Apache. See the YoLinux Networking Tutorial to specify multiple IP addresses for one NIC (Network Interface Card). Use the Apache configuration file directive Listen XXX.XXX.XXX.XXX, where the IP address is unique for each instance of Apache.

Apache Man Pages:

  • httpd - Apache Hypertext Transfer Protocol Server
  • apachectl - Apache HTTP Server Control Interface
  • ab - Apache HTTP server bench-marking tool
  • htdigest - manage user files for digest authentication
  • htpasswd - Manage user files for basic authentication
  • logresolve - Resolve IP-addresses to hostnames in Apache log files
  • rotatelogs - Piped logging program to rotate Apache logs

Also see the local online Apache configuration manual: http://localhost/manual/.

Apache Red Hat / Fedora Core GUI configuration:

GUI configuration tool:

  • Red Hat EL 4/5, Fedora 2-10: /usr/bin/system-config-httpd
  • Red Hat 8/9, Fedora Core 1: /usr/bin/redhat-config-httpd

Red Hat Apache httpd configuration tool

Adding web site login and password protection: See the YoLinux tutorial on web site password protection.

Log file analysis:

Scanning the Apache web log files will not provide meaningful statistics unless they are graphed or presented in an easy to read fashion. The following packages to a good job of presenting site statistics.

Web site statistic services:

Load testing your server:

Apache Links:

Log file analysis using Analog:


  • Red Hat / Fedora: yum install analog
  • Ubuntu / Debian: apt-get install analog
Installation packages also available from the Analog downloads page.

Configuration file: /etc/analog.cfg
LOGFILE /var/log/httpd/your-domain.com-access_log* http://www.your-domain.com
UNCOMPRESS *.gz,*.Z "gzip -cd"
SUBTYPE *.gz,*.Z
OUTFILE /home/user1/public_html/analog/Report.html
HOSTNAME "YourDomain.com"
HOSTURL  http://www.your-domain.com


REQINCLUDE pages                  # Request page stats only
One can view the settings which be used with your configuration file (also good for debugging): analog -settings

Make Analog images available to the users report: ln -s /usr/share/analog/images/* /home/user1/public_html/analog

Log file location:

  • Red Hat / Fedora: /var/log/httpd/
  • Ubuntu / Debian: /var/log/apache2/

The Directive "ALL ON" turns on all of the following:
Analog DirectiveDescription
MONTHLY ON one line for each month
WEEKLY ON one line for each week
DAILYREP ON one line for each day
DAILYSUM ON one line for each day of the week
HOURLYREP ON one line for each hour of the day
GENERAL ON the General Summary at the top
REQUEST ON which files were requested
FAILURE ON which files were not found
DIRECTORY ON Directory Report
HOST ON which computers requested files
ORGANISATION ON which organizations they were from
DOMAIN ON which countries they were in
REFERRER ON where people followed links from
FAILREF ON where people followed broken links from
SEARCHQUERY ON the phrases and words they used...
SEARCHWORD ON ...to find you from search engines
BROWSERSUM ON which browser types people were using
OSREP ON and which operating systems
FILETYPE ON types of file requested
SIZE ON sizes of files requested
STATUS ON number of each type of success and failure

Cron job to handle multiple domains: /etc/cron.daily/analog
cp /opt/etc/analog-domain1.com.cfg      /etc/analog.cfg
cp /opt/etc/analog-domain2.com.cfg      /etc/analog.cfg



Measuring Web Server Performance:

See the YoLinux.com web server bench-marking tutorial.

File transfer and FTPd and FTP user account configuration:

The File Transfer Protocol (FTP) is often used to upload and download files to a web server. FTP is unencrypted and is no longer suited for today's public internet. A private secure network is required for use of unencrypted FTP. Typically one will use rsync over ssh (tutorial) or sFTP. File transfers are commanded from a client application to transfer files to/from a server.

Many FTP programs exist:

For hostile environments set up a chrooted environment for an sftp encrypted connection and the rssh restricted shell for OpenSSH. See the YoLinux.com internet security tutorial for Linux sftp and rssh configuration

Also see the preferred chrooted sftp configuration for OpenSSH 4.9+

FTP Linux clients:

  • FileZilla: FTP/sFTP client GUI
  • gftp: GUI GTK+ Multi-threaded client. File transfer directory browsing and compare. Multiple protocols: FTP, FTPS (control connection only), HTTP, HTTPS, SSH and FSP protocols. Proxy support. Comes with Red Hat / Fedora Core.
  • KFTPgrabber: GUI KDE based client.simultaneous FTP sessions in separate tabs. Ability to limit upload and download speed.
  • kbear: GUI KDE based client. Connect to multiple servers, transfer files, directory browsing, file content browsing. Comes with S.U.S.e. Linux.
  • ftp: (/usr/kerberos/bin/ftp) kerberos enabled console ftp client. (RPM package FC3: krb5-workstation)

Basic user security:

When hosting web sites, there is no need to grant a shell account which only allows the server to have more potential security holes. Current systems can specify the user to have only FTP access with no shell by granting them the "shell" /sbin/nologin provided with the system or the "ftponly" shell described below. The shell can be specified in the file /etc/passwd of when creating a user with the command adduser -s /sbin/nologin user-id

[Potential Pitfall]: Ubuntu - Setting the shell to the pre-configured shell /bin/false will NOT allow vsftp access. One must create the shell "ftponly" as defined below to allow vsftp access with no shell.

  1. Disable remote telnet login access allowing FTP access only:

    Change the shell for the user in /etc/passwd from /bin/bash to be /opt/bin/ftponly.


    Create file: /opt/bin/ftponly.
    Protection set to -rwxr-xr-x 1 root root
    with the command: chmod ugo+x /opt/bin/ftponly
    Contents of file:

    # ftponly shell
    trap "/bin/echo Sorry; exit 0" 1 2 3 4 5 6 7 10 15
    /bin/echo "********************************************************************"
    /bin/echo "    You are NOT allowed interactive access."
    /bin/echo "     User accounts are restricted to ftp and web access."
    /bin/echo "  Direct questions concerning this policy to $Admin."
    /bin/echo "********************************************************************"
    # C'ya
    exit 0

    The last step is to add this to the list of valid shells on the system.
    Add the line /opt/bin/ftponly to /etc/shells.

    Sample file contents: /etc/shells

    See man page on /etc/shells.

    An alternative would be to assign the shell /bin/false or /sbin/nologin which became available in later releases of Red Hat, Debian and Ubuntu. In this case the shell /bin/false or /sbin/nologin would have to be added to /etc/shells to allow them to be used as a valid shell for FTP while disabling ssh or telnet access.

  2. Set file quotas to limit user account.

For more on Linux security see the: YoLinux.com Internet web site Linux server security tutorial

Domain Name Server (DNS) configuration using Bind version 8 or 9:

Two of the most popular ways to configure the program Bind (Berkeley Internet Domain software) to perform DNS services is in the role of (1) ISP or (2) Web Host.

  1. In an ISP configuration for clients (web surfers) connected to the internet, the DNS server must resolve IP addresses for any URL the user wishes to visit. (See DNS caching server)
  2. In a purely web hosting configuration, Bind will only resolve for the IP addresses of the domains which are being hosted. This is the configuration which will be discussed and is often called an "Authoritative-only Nameserver".

When resolving IP addresses for a domain, Internic is expecting a "Primary" and a "Secondary" DNS name server. (Sometimes called Master and Slave) Each DNS name server requires the file /etc/named.conf and the files it points to. This is typically two separate computer systems hosted on two different IP addresses. It is not necessary that the Linux servers be dedicated to DNS as they may run a web server, mail server, etc.

Note on Bind versions: Red Hat versions 6.x used Bind version 8. Release 7.1 of Red Hat began using Bind version 9 and the GUI configuration tool bindconf was introduced for those of you that like a pretty point and click interface for configuration.

Installation Packages:

  • Red Hat / Fedora Core / CentOS: bind, bind-chroot, bind-libs, bind-utils, system-config-bind
    • bind-chroot: Security jail for operation of bind.
    • bind-utils: Utility commands like nslookup, host, dig
    • system-config-bind: GUI config tool system-config-bind and related configuration files (/etc/security/console.apps/bindconf).
    • caching-nameserver: We will not be covering this as it is not required for web hosting. This is used by internet providers so their clients can cache the DNS entries of the sites they are visiting.
  • Ubuntu (dapper/hardy/natty) / Debian: bind9

Configuration files:

Red Hat / Fedora / CentOS:
FileDescriptionDirectoryChrooted Directory
named.confPrimary/Secondary DNS server configuration.
(See default file /usr/share/doc/bind-9.X.X/sample/etc/named.conf)
named.root.hintsConfiguration for recursive service. Required for all zones.
(See default file /usr/share/doc/bind-9.X.X/sample/etc/named.root.hints)
namedRed Hat system variables./etc/sysconfig/no change
rndc.keyPrimary/Secondary DNS server configuration./etc//var/named/chroot/etc/
Zone filesConfiguration files for each domain. Create this file to resolve host name internet queries i.e. define IP address of web (www) and mail servers in the domain./var/named//var/named/chroot/var/named/

Debian / Ubuntu:
FileDescriptionDirectoryChrooted Directory
Primary/Secondary DNS server configuration./etc/bind//var/bind/chroot/etc/bind/
rndc.keyPrimary/Secondary DNS server configuration./etc//var/bind/chroot/etc/
Zone filesConfiguration files for each domain./var/bind/data//var/bind/chroot/var/bind/data/

Primary server (master):
File: named.conf Red Hat / Fedora Core / CentOS: /etc/named.conf (chroot dir: /var/named/chroot/etc/named.conf) and /etc/sysconfig/named for system variables.
Ubuntu / Debian: /etc/bind/named.conf Place local definitions in /etc/bind/named.conf.options and /etc/bind/named.conf.local

Simple example: (no views)
options {                                     - Ubuntu stores options in /etc/bind/named.conf.options
        version "Bind";                       - Don't disclose real version to hackers
        directory "/var/named";               - Specified so relative path names can be used. Full path names still allowed.
        allow-transfer { XXX.XXX.XXX.XXX; };  - IP address of secondary DNS
        recursion no;
        auth-nxdomain no;                     - conform to RFC1035. (default)
        fetch-glue no;                  - Bind 8 only! Not used by version 9

zone "localhost" {
        type master;
        file "/etc/bind/db.local";
zone "0.0.127.in-addr.arpa" {
        type master;
        file "/etc/bind/db.127";

zone "your-domain.com"{                 - Ubuntu separates the zone definitions into /etc/bind/named.conf.local 
        type master;                    - Specify master, slave, forward or hint
        file "data/named.your-domain.com"; 
        notify yes;                     - slave servers are notified when the zone is updated.
        allow-update { none; };         - deny updates from other hosts (default: none)
        allow-query { any; };           - allow clients to query this server (default: any)
zone "your-domain-2.com"{
        type master;
        file "data/named.your-domain-2.com";
        notify yes;

  • The omission of zone ".". Required if providing a recursive service.
  • Ubuntu includes the separated file of zone directives using the directive:
    include "/etc/bind/named.conf.local";

BIND Views: The BIND naming service can support "views" which allow various sub-networks (i.e. private internal or public external networks) to have a different domain name resolution result.
  • If no views are specified then use the configuration shown above.
  • The match-up between the "view" and the view client which receives the DNS information is specified by the match-clients statement.
  • If even one view is specified, then ALL zones MUST be associated with a "view".
  • Bind 9 allows for views which allow different zones to be served to different types of clients, localhost, private networks and public networks. This maps to the three view names "localhost_resolver", "internal" and "external":
    • localhost_resolver: Supports name resolution for the system (localhost) using BIND. Support for use of bind also has to be configured in /etc/nsswitch.conf
    • internal: User specified Local Area Network (LAN). If not used to support a local private LAN, remove (or comment out) this view.
    • external: The general public internet defined as client "any".
  • If you are only setting up a caching name server, then only specify the view "localhost_resolver" (delete all other views).
  • In order to support a DNS for internet domains using views, one will have to configure an "external" view

Typical Red Hat Enterprise 5 example: (Bind 9.3.4 with three "views")
        directory "/var/named"; // the default
        dump-file               "data/cache_dump.db";
        statistics-file         "data/named_stats.txt";
        memstatistics-file      "data/named_mem_stats.txt";

    //  By default, SELinux policy does not allow named to modify the /var/named
    //  directory, so put the default debug log file in data/ :
        channel default_debug {
                file "data/named.run";
                severity dynamic;
view "localhost_resolver"
    //  This view sets up named to be a localhost resolver ( caching only nameserver ).
    //  If all you want is a caching-only nameserver, then you need only define this view:
    match-clients           { localhost; };
view "internal"
    // This view will contain zones you want to serve only to "internal" clients
    // that connect via your directly attached LAN interfaces - "localnets" .
    // For local private LAN. Not covered in this tutorial.
    // Delete this view if web hosting with no local LAN.
    match-clients           { localnets; };
key ddns_key
        algorithm hmac-md5;
        secret "use /usr/sbin/dns-keygen to generate TSIG keys";
view    "external"
    // This view will contain zones you want to serve only to "external" 
    // public internet clients. This is covered below.
    match-clients           { any; };

Default configuration files: Red Hat may supply the default configuration in: /usr/share/doc/bind-9.X.X/sample/etc/named.conf
  • cp /usr/share/doc/bind-9.X.X/sample/etc/named.conf /var/named/chroot/etc
  • cp /usr/share/doc/bind-9.X.X/sample/etc/named.root.hints /var/named/chroot/etc
  • chcon -u system_u -r object_r -t named_conf_t /var/named/chroot/etc/named.conf /var/named/chroot/etc/named.root.hints

view "localhost_resolver": If supporting a caching DNS server (not required to support a web domain) you will also need the files:
  • cp /usr/share/doc/bind-9.X.X/sample/etc/named.rfc1912.zones /var/named/chroot/etc
  • cp /usr/share/doc/bind-9.X.X/sample/var/named/localdomain.zones /var/named/chroot/var/named
    also from /usr/share/doc/bind-9.X.X/sample/var/named/: localhost.zones, named.local, named.zero, named.broadcast, named.ip6.local, named.root

view "external": (master) - details -
view    "external"
/* This view will contain zones you want to serve only to "external" clients
 * that have addresses that are not on your directly attached LAN interface subnets:
        match-clients           { any; };
        match-destinations      { any; };
        allow-transfer { XXX.XXX.XXX.XXX; };  - IP address of secondary DNS

        recursion no;
        // you'd probably want to deny recursion to external clients, so you don't
        // end up providing free DNS service to all takers

        // all views must contain the root hints zone:
        include "/etc/named.root.hints";

        // These are your "authoritative" external zones, and would probably
        // contain entries for just your web and mail servers:

        zone "your-domain.com" {
                type master;
                file "/var/named/data/external/named.your-domain.com";
                notify yes;
                allow-update { none; };
        // You can also add the zones as a separate file like they do in Ubuntu by adding the following statement
        include "/etc/named.conf.local";      

DNS key:

Use the following command /usr/sbin/dns-keygen to create a key. Add this key to the "secret" statement as follows:
key ddns_key
        algorithm hmac-md5;

Man Pages:

Forward Zone File: /var/named/named.your-domain.com

Red Hat 9 / CentOS 3: /var/named/named.your-domain.com
Red Hat EL4/5/6, Fedora 3+, CentOS 4/5/6: [Chrooted] /var/named/chroot/var/named/data/named.your-domain.com
Red Hat EL4/5/6, Fedora 3+, CentOS 4/5/6: /var/named/data/named.your-domain.com
Ubuntu / Debian: /etc/bind/data/named.your-domain.com
$TTL 604800         - Bind 9 (and some of the later versions of Bind 8) requires $TTL statement. 
                     Measured in seconds. This value is 7 days.
your-domain.com.    IN      SOA  ns1.your-domain.com.  hostmaster.your-domain.com. (
   2000021600 ; serial     - Many people use year+month+day+integer as a system.
   86400 ; refresh         - How often secondary servers (in seconds) should check in for changes in serial number. (86400 sec = 24 hrs)
   7200 ; retry            - How long secondary server should wait for a retry if contact failed.
   1209600 ; expire        - Secondary server to purge info after this length of time.
   86400 ) ; default_ttl   - How long data is held in cache by remote servers.
       IN A       XXX.XXX.XXX.XXX  - Note that this is the default IP address of the domain. 
                                     I put the web server IP address here so that domain.com points to the same servers as www.domain.com
; Name servers for the domain
       IN NS         ns1.your-domain.com.
       IN NS         ns2.your-domain.com.
; Mail server for domain
       IN MX    5    mail               - Identify "mail" as the node handling mail for the domain. Do NOT specify an IP address!
; Nodes in domain
node1  IN A          XXX.XXX.XXX.XXX    - Note that this is the IP address of node1
ns1    IN A          XXX.XXX.XXX.XXX    - Optional: For hosting your own primary name server. Note that this is the IP address of ns1
ns2    IN A          XXX.XXX.XXX.XXX    - Optional: For hosting your own secondary name server. Note that this is the IP address of ns2
mail   IN A          XXX.XXX.XXX.XXX    - Identify the IP address for node mail.
; Aliases to existing nodes in domain
www    IN CNAME      node1              - Define the webserver "www" to be node1.
ftp    IN CNAME      node1              - Define the ftp server to be node1.

DNS record types and format:

DNS recordDescription and Format
SOA Start of Authority: Primary domain server and contact info
Note that there is a period following the primary domain server and contact email.
Note that the email address is in the form where the first period represents the "@" symbol of the email address.
your-domain.com in SOA ns1.your-domain.com.  webmaster.your-domain.com.
@ in SOA ns1.your-domain.com.  webmaster.your-domain.com.
[Potential Pitfall]: Incorrect specification of the primary name server may result in the following message in /var/log/messages:
view localhost_resolver: received notify for zone 'your-domain.com': not authoritative
SOA attributeDescription
serialNever use a value greater than 2147483647 for a 32 bit processor.
Increment to a higher value to indicate an update to the slave server.
refreshTime increment (seconds) between update checks of the serial number with the primary server
retryTime elapsed before a slave will contact the primary server if a connection failed
expireTime till primary server information is considered invalid and should be refreshed if there is a new DNS query
minimumTime for DNS servers should hold domain information in their cache before purging
INIndicate Internet.
NSSpecify the Authoritative Name servers for the domain.
ASpecify the IP address associated with the host name.
Format: hostname IN A XXX.XXX.XXX.XXX
Note that in my example, no hostname is specified for the first record. This will define the default for the domain.
CNAMESpecify an alias for the host name.
MXMail exchange record. Specify a priority number for the primary and back-up mail servers. The lowest number indicates the default mail server for the domain
PTRUsed to specify the reverse DNS lookup

MX records for 3rd party off-site mail servers:
your-domain.com.    IN MX  10 mail1.offsitemail.com.
your-domain.com.    IN MX  20 mail2.offsitemail.com.
Append to the above example file.

SPF Record:

To thwart spammers from pretending to be sending email from your domain (spoofing), use your DNS to specify your outbound email server.

Add a Sender Policy Framework (SPF) record as follows (pick one solution):

  • Specify the inbound email server as defined by the DNS MX record is also your outbound email server:
    ; Mail server for domain
                 IN MX    5      mail
    ; SPF allow MX mail server to send email for the domain
    your-domain.com. IN TXT   "v=spf1 a mx -all"
    • v=spf1: All SPF records all start with "v=spf1"
    • -all: fail network address if it does not pass the rules specified (use this)
    • +all: pass network address
    • ~all: soft fail
    • a: signifies that the host is authorized to send the emails on behalf of the domain
    • mx: specify the MX inbound mail server to also be the outbound mail server

  • Specify the IP address of the outbound email server:
    your-domain.com. IN TXT   "v=spf1 a mx ip4:XXX.XXX.XXX.XXX -all"
    • Use ip4 or ip6 to specift an IP version 4 or version 6 network address

  • Specify an alternate email service provider (in this case Google gmail) to also grant permission to send email on behalf of the domain:
    your-domain.com. IN TXT   "v=spf1 a mx include:_spf.google.com -all"
    • include: authorize outbound hosts outside of your domain
These are SPF examples for Bind 9 DNS. Note that the MX record specifies the email server to receive email and SPF defines the outbound server.

Initial configuration:

Note that Red Hat may supply the default zone configuration in: /usr/share/doc/bind-9.X.X/sample/var/named/
  • cp /usr/share/doc/bind-9.X.X/sample/var/named/localhost.zone /var/named/chroot/var/named/data/
  • cp /usr/share/doc/bind-9.X.X/sample/var/named/localdomain.zone /var/named/chroot/var/named/data/
  • cp /usr/share/doc/bind-9.X.X/sample/var/named/named.broadcast /var/named/chroot/var/named/data/
  • cp /usr/share/doc/bind-9.X.X/sample/var/named/named.ip6.local /var/named/chroot/var/named/data/
  • cp /usr/share/doc/bind-9.X.X/sample/var/named/named.zero /var/named/chroot/var/named/data/
  • cp /usr/share/doc/bind-9.X.X/sample/var/named/named.local /var/named/chroot/var/named/data/
  • cp /usr/share/doc/bind-9.X.X/sample/var/named/named.root /var/named/chroot/var/named/data/
  • cd /var/named/chroot/var/named/data/
  • chcon -u system_u -r object_r -t named_cache_t localhost.zone localdomain.zone named.broadcast named.ip6.local named.zero named.root named.local
A file suffix of "zone" is also common i.e. your-domain.com.zone

Secondary server (slave):
File: named.conf Red Hat / Fedora Core / CentOS: /etc/named.conf
Ubuntu / Debian: /etc/bind/named.conf
Simple example with no views:
options {                               - Ubuntu stores options in /etc/bind/named.conf.options
        version "Bind";                 - Don't disclose real version to hackers
        directory "/var/named";
        allow-transfer { none; };    - Slave is not transfering updates to anyone else
        recursion no;
        auth-nxdomain no;               - conform to RFC1035. (default)
        fetch-glue no;                - Bind 8 only! Not used by version 9
zone "localhost" {
        type master;
        file "/etc/bind/db.local";       - Ubutu: /etc/bind/db.local, Red Hat: /var/named/named.local
zone "0.0.127.in-addr.arpa" {
        type master;
        file "/etc/bind/db.127";

zone "your-domain.com"{
        type slave;          
        file "named.your-domain.com";   - Specify slaves/named.your-domain.com for RHEL chrooted bind
        masters { XXX.XXX.XXX.XXX; };   - IP address of primary DNS
zone "your-domain-2.com"{
        type slave;          
        file "named.your-domain-2.com";
        masters { XXX.XXX.XXX.XXX; };

view "external": (slave)
view    "external"
        match-clients           { any; };
        match-destinations      { any; };
        allow-transfer { none; };  - Slave does not transfer to anyone, slave receives
        recursion no;
        include "/etc/named.root.hints";

        zone "your-domain.com" {
                type slave;
                file "/var/named/slaves/external/named.your-domain.com";
                notify no;                  - Slave does not notify, slave is notified by master
                masters { XXX.XXX.XXX.XXX; }; - State IP of master server
Note: RHEL, CentOS, Fedora use chrooted directory structure permissions which require the use of the slaves sub-directory /var/named/slaves

Slave Zone Files: These are transfered from master to slave and cached by slave. There is no need to generate a zone file on the slave.

Additional Information:

[Potential Pitfall]: Ubuntu dapper/hardy/natty - Path names used can not violate Apparmor security rules as defined in /etc/apparmor.d/usr.sbin.named. Note that the slave files are typically named "/var/lib/bind/named.your-domain.com" as permitted by the security configuration.

[Potential Pitfall]: Ubuntu dapper/hardy/natty - Create log file and set ownership and permission for file not created by installation:

  • touch /var/log/bindlog
  • chown root.bind /var/log/bindlog
  • chmod 664 /var/log/bindlog

[Potential Pitfall]: Error in /var/log/messages:

transfer of 'yolinux.com/IN' from XXX.XXX.XXX.XXX#53: failed while receiving responses: permission denied
Named needs write permission on the directory containing the file. This condition often occurs for a new "slave" or "secondary" name server where the zone files do not yet exist.
The default (RHEL, CentOS, Fedora, ...):
  • drwxr-x--- 4 root named 4096 Aug 25 2004 named
  • drwxrwx--- 2 named named 4096 Sep 17 20:37 slaves

Fix: In named.conf specify that the slaves to go to slaves directory /var/named/chroot/var/named/slaves with the directive:
file "slaves/named.your-domain.com";

Bind Defaults:

  • Uses port 53 if none is specified with the listen-on port statement.
  • Bind will use random ports above port 1024 for queries. For use with firewalls expecting all DNS traffic on port 53, specify the following option statement in /etc/named.conf
    query-source address * port 53;
    query-source-v6 port 53;
  • Logging is to /var/log/messages

After the configuration files have been edited, restart the name daemon.

/etc/init.d/named restart

(Note: Ubuntu / Debian restart: /etc/init.d/bind9 restart)

Bind zone transfers work best if the clocks of the two systems are synchronised. See the YoLinux SysAdmin Tutorial: Time and ntpd

File: /var/named/named.your-domain.com This is created for you by Bind on the slave (secondary) server when it replicates from Primary server.

DNS GUI configuration:

  • Red Hat EL 4/5, Fedora 2-10: /usr/bin/system-config-bind
  • Red Hat 8/9, Fedora Core 1: /usr/bin/redhat-config-bind

Red Hat bind configuration tool Red Hat bind configuration tool: SOA zone

Test DNS:

Must install packages:

  • Red Hat / Fedora Core / SuSE: bind-utils
  • Ubuntu (dapper/hardy/natty) / Debian: bind9-host
Test the name server with the host command in interactive mode:
   host  node.domain-to-test.com your-nameserver-to-test.domain.com

Note: The name server may also be specified by IP address.


Test the name server with the nslookup command in interactive mode:

> server your-nameserver-to-test.domain.com > node.domain-to-test.com > exit

Test the MX record if appropriate:

   nslookup -querytype=mx domain-to-test.com

   host -t mx domain-to-test.com

Test using the dig command:

   dig @name-server domain-to-query


   dig @IP-address-of-name-server domain-to-query

Test your DNS with the following DNS diagnostics web site: DnsStuff.com

Extra logging to monitor Bind:

Add the following to your /etc/named.conf file.
logging {
        channel bindlog {
                           // Keep five old versions of the log-file (rotates logs)
                           file "/var/log/bindlog"  versions 5 size 1m;
                           print-time yes;
                           print-category yes;
                           print-severity yes;
/*      If you want to enable debugging, eg. using the 'rndc trace' command,
 *      named will try to write the 'named.run' file in the $directory (/var/named).
 *      By default, SELinux policy does not allow named to modify the /var/named directory,
 *      so put the default debug log file in data/ :
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        category xfer-out { bindlog; };         - Zone transfers
        category xfer-in  { bindlog; };         - Zone transfers
        category security { bindlog; };         - Approved/unapproved requests

//      The following logging statements, panic, insist and response-checks are 
//      valid for Bind 8 only. Do not user for version 9.
        category panic { bindlog; };            - System shutdowns
        category insist { bindlog; };           - Internal consistency check failures
        category response-checks { bindlog; };  - Messages

Chroot Bind for extra security:

Note: Most modern Linux distributions default to a "chrooted" installation. This technique runs the Bind name service with a view of the filesystem which changes the definition of the root directory "/" to a directory in which Bind will operate. i.e. /var/named/chroot.

The following example uses the Red Hat RPM bind-8.2.3-0.6.x.i386.rpm. Applies to Bind version 9 as well.

The latest RedHat bind updates run the named as user "named" to avoid a lot of earlier hacker exploits. To chroot the process is to create an even more secure environment by limiting the view of the system that the process can access. The process is limited to the chrooted directory assigned.

The chroot of the named process to a directory under a given user will prevent the possibility of an exploit which at one time would result in root access. The original default RedHat configuration (6.2) ran the named process as root, thus if an exploit was found, the named process will allow the hacker to use the privileges of the root user. (no longer true)

Named Command Sytax:

   named -u user -g group -t directory-to-chroot-to
    named -u named -g named -t /opt/named

When chrooted, the process does not have access to system libraries thus a local lib directory is required with the appropriate library files - theoretically. This does not seem to be the case here and as noted above in chrooted FTP. It's a mystery to me but it works???? Another method to handle libraries is to re-compile the named binary with everything statically linked. Add -static to the compile options. The chrooted process should also require a local /etc/named.conf etc... but doesn't seem to???

Script to create a chrooted bind environment:

cd /opt
mkdir named
cd named
mkdir etc
mkdir bin
mkdir var
cd var
mkdir named
mkdir run
cd ..
chown -R named.named bin etc var

You can probably stop here. If your system acts like a chrooted system should, then continue with the following:
cp -p /etc/named.conf etc
cp -p /etc/localtime  etc
cp -p /bin/false bin
echo "named:x:25:25:Named:/var/named:/bin/false" > etc/passwd
echo "named:x:25:" > etc/group
touch  var/run/named.pid 

if [ -f /etc/namedb ]
   cp -p /etc/namedb etc/namedb

mkdir dev
cd dev

# Create a character unbuffered file.
mknod -m ugo+rw null c 1 3     

cd ..
chown -R named.named bin etc var

Add changes to the init script: /etc/rc.d/init.d/named
# named           This shell script takes care of starting and stopping
#                 named (BIND DNS server).
# chkconfig: - 55 45
# description: named (BIND) is a Domain Name Server (DNS) \
# that is used to resolve host names to IP addresses.
# probe: true

# Source function library.
. /etc/rc.d/init.d/functions

# Source networking configuration.
. /etc/sysconfig/network

# Check that networking is up.
[ ${NETWORKING} = "no" ] && exit 0

[ -f /etc/sysconfig/named ] && . /etc/sysconfig/named 

[ -f /usr/sbin/named ] || exit 0

[ -f /etc/named.conf ] || exit 0


start() {
        # Start daemons.
        echo -n "Starting named: "
        daemon named -u named -g named -t /opt/named   # Change made here
 	[ $RETVAL -eq 0 ] && touch /var/lock/subsys/named
	return $RETVAL
stop() {
        # Stop daemons.
        echo -n "Shutting down named: "
        killproc named
	[ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/named
	return $RETVAL
rhstatus() {
	/usr/sbin/ndc status
	return $?
restart() {
reload() {
	/usr/sbin/ndc reload
	return $?
probe() {
	# named knows how to reload intelligently; we don't want linuxconf
	# to offer to restart every time
	/usr/sbin/ndc reload >/dev/null 2>&1 || echo start
	return $?

# See how we were called.
case "$1" in
		[ -f /var/lock/subsys/named ] && restart || :
        	echo "Usage: named {start|stop|status|restart|condrestart|reload|probe}"
		exit 1

exit $?

Note: The current version of bind from the RedHat errata updates and security fixes (http://www.redhat.com/support/errata/) runs the named process as user "named" in the home (not chrooted) directory /var/named with no shell available. (named -u named) This should be secure enough. Proceed with a chrooted installation if your are paranoid.


Chrooted DNS configuration:

Modern releases of Linux (i.e. Fedore Core 3, Red Hat Enterprise Linux 4) come pre-configured to use "chrooted" bind. This security feature forces even an exploited version of bind to only operate within the "chrooted" jail /var/named/chroot which contains the familiar directories:

  • /var/named/chroot/etc: Configuration files
  • /var/named/chroot/dev: devices used by bind:
    • /dev/null
    • /dev/random
    • /dev/zero
    (Real devices created with the mknod command.)
  • /var/named/chroot/var: Zone files and configuration information.
These directories are generated and configured by the Red Hat/Fedora RPM package "bind-chroot".

If building from source you will have to generate this configuration manually:

  • mkdir -p /var/named/chroot
  • mkdir /var/named/chroot/dev
  • mknod /var/named/chroot/dev/null c 1 3
  • mknod /var/named/chroot/dev/zero c 1 5
  • mknod /var/named/chroot/dev/random c 1 8
  • chmod 666 -R /var/named/chroot/dev
  • mkdir -p /var/named/chroot/etc
  • ln -s /var/named/chroot/etc/named.conf /etc/named.conf
  • mkdir -p /var/named/chroot/var/named
  • ln -s /var/named/chroot/var/named/named.XXXX /var/named/named.XXXX
  • ln -s /var/named/chroot/var/named/named.YYYY /var/named/named.YYYY
  • ...
  • mkdir -p /var/named/chroot/var/named/slaves
  • mkdir -p /var/named/chroot/var/named/data
  • mkdir -p /var/named/chroot/var/run
  • mkdir -p /var/named/chroot/var/tmp
  • chown -R named:named /var/named/chroot
  • chown -R root:named /var/named/chroot/var/named

Load Balancing of servers using Bind: DNS Round-Robin:
This will populate DNS caching name servers around the world with different IP addresses for your web server www.your-domain.com

File: /var/named/data/named.your-domain.com
$TTL 604800
your-domain.com.    IN      SOA  ns1.your-domain.com.  hostmaster.your-domain.com.


www   IN  A
www   IN  A
www   IN  A
www   IN  A
www   IN  A
www   IN  A

  • This example will resolve the www.your-domain.com URL to each of the IP addresses listed, one at a time for each request. First request will resolve to, the second request will resolve to, etc.
  • A perfectly even load balance is not possible becaused network service providers run DNS caching servers which hold the resolved IP address for a different number of users.
  • Using multiple CNAME's to rotate records is no longer permissible in bind9.
  • Listing a record multiple times with the same IP address will not change the load sharing. Bind will ignore duplicate records.
  • Reducing the time to live (TTL) will cause load sharing to take place more frequently thus responding to a change in servers more quickly.

Also see lbnamed: lbnamed load balancing named

Bind/DNS Links:

Domain name registration:

Note that the Name registrations policies for the registrars are stated at ICANN.org.

  • You must renew with the same registrar within five days BEFORE the expiration date. There is no rule for afterwards.
  • Most free a domain name 30 days after it expires.

Web Server Load Balancing:

Load balancing becomes important if your traffic volume becomes too great for either your server or network connection or both. Multiple options are available for load balancing.
  • DNS round-robin: Discussed above, this uses DNS to point users to random server in a list of appropriate servers. This spreads the load among the servers in the list.
  • Use a Linux Virtual Server to Create a Load Balance Cluster. See next section below.
  • Run a reverse proxy. See nginx ("engine X"). From a single external internet network connection, route http, smtp, imap or pop3 traffic to various servers on an internal network. Results are pushed back to the nginx proxy for routing to the internet (no caching).
  • Run the Apache httpd web server module "mod_proxy" to offload processing of dynamic content to another web server. This acts as a reverse proxy, routing external traffic to various servers on an internal network.

Using a Linux Virtual Server to Create a Load Balance Cluster:

You can use a single Linux server to forward requests to a cluster of servers using iptables for IP masquerading and IPVsadm to scale your load. The load balancing server receiving and routing the requests is called the "Linux Virtual Server" (LVS). The LVS receives the requests which are passed to the real servers which process and reply to the request. This reply is forwarded to the client by the LVS.

This feature is available with the Linux 2.4/2.6 kernel. (If compiling kernel: Networking Options + IP: Virtual Server Configuration)

Configuration: This example will load balance http traffic to three web servers and ftp traffic to a fourth server.

  • Enable Forwarding: (Also see YoLinux Networking Tutorial: Enable Forwarding)
    echo "1" > /proc/sys/net/ipv4/ip_forward
  • Enable IP Masquerading:
    iptables -t nat -P POSTROUTING DROP
    iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
    For more on IP Masquerading, iptables and subnet addresses, see the YoLinux network gateway tutorial.
  • Enable virtual server:
    • Create virtual service and choose scheduler for http (80) and ftp (21):
      ipvsadm -A -t -s wlc
      ipvsadm -A -t -s wrr
      Command directives:
      • A: Add a virtual service defined by IP address, port number, and protocol.
      • -t: Use TCP service host:port
      • -s: scheduler:
        • rr: Robin Robin: distributes jobs equally amongst the avail- able real servers.
        • wrr: Weighted Round Robin.
        • lc: Least-Connection: assigns more jobs to real servers with fewer active jobs.
        • wlc: (Default) Weighted Least-Connection: assigns more jobs to servers with fewer jobs and relative to the real server's weight.
        • lblc, lblcr, dh, sh, sed, nq. See man page.
    • Configure load balancing cluser.
      ipvsadm -a -t -r -m
      ipvsadm -a -t -r -m -w 2
      ipvsadm -a -t -r -m
      ipvsadm -a -t -r -m
      Command directives:
      • -r: Real server.
      • -m: Use masquerading also known as network address translation (NAT)
      • -w: Weight is an integer specifying the capacity of a server relative to the others in the pool. The valid values of weight are 0 through to 65535. The default is 1.


Managing Web Server Daemons:

To view if these services are running, type ps -aux and look for the httpd, inetd and named services (daemons). These are background processes necessary to perform the server tasks.

   root       681  0.0  0.5  2304  744 ?        S    Sep09   0:01 named
   nobody   28123  0.0  1.1  3036 1420 ?        S    Oct06   0:00 httpd
   nobody   28186  0.0  0.7  3044  896 ?        S    Oct06   0:00 httpd
   root       385  0.0  0.1  1136  232 ?        S    Sep09   0:00 inetd
A new installation will most likely NOT start the named background process which may be started manually after configuration.
See the YoLinux Init Process Tutorial for more information.
The inetd (or xinetd) background process is the Internet daemon which starts FTP when an ftp request is made.

Sys Admin Script:

Script to prepare an account: (Red Hat/Fedora)

# Author Greg Ippolito
# Requires: /opt/etc/AccountDefaults/pathmsg favicon.ico  mwh-mini_tr.gif etc.
#           /opt/bin/ftponly
#   You must be root to run this script.
if [ $# -eq 0 ]
   echo "Enter user id as a command argument"
else if [ -r /home/$1 ]
   echo "User's home directory already exists"
   echo "1)  Create user."
   adduser -m $1

   echo "2)  Set user Password."
   passwd $1

   echo "3)  Add read access to user directory so apache can read it."
   cd /home
   chmod ugo+rx $1
   cd $1

   echo "4)  Create web directories."
   mkdir public_html
   chown $1.$1 public_html
   chcon -R -h -u system_u -r object_r -t httpd_sys_content_t public_html
   cd public_html
   mkdir images
   chown $1.$1 images
   chcon -R -h -u system_u -r object_r -t httpd_sys_content_t images

   # Block potential for unauthenticated logins
   cd ../
   touch .rhosts
   chmod ugo-xrw .rhosts

   echo "5)  Create default web page"
   sed "/HEADING/s!HEADING!$1!" /opt/etc/AccountDefaults/default-index.html > index.html
   cp -p /opt/etc/AccountDefaults/favicon.ico .
   cp -p /opt/etc/AccountDefaults/default-logo.gif ./images
   cp -p /opt/etc/AccountDefaults/robots.txt .
   chown $1.$1 index.html favicon.ico robots.txt
   chcon -R -h -t httpd_sys_content_t index.html favicon.ico robots.txt
   chcon -R -h -t httpd_sys_content_t images/default-logo.gif

   echo "6)  Edit /etc/passwd file - change user shell to /opt/bin/ftponly"
   cp -p  /etc/passwd /etc/passwd-`date +%m%d%y`
   sed "/^$1/s!/bin/bash!/opt/bin/ftponly!" /etc/passwd-`date +%m%d%y` > /etc/passwd

#wu-ftp# Requires: /etc/ftpaccess guestuser restrict-uid
#wu-ftp#   echo "7)  Add user to /etc/ftpaccess file"
#wu-ftp#   cp -p  /etc/ftpaccess /etc/ftpaccess-`date +%m%d%y`
#wu-ftp#   sed "/^guestuser/s!guestuser !guestuser $1 !" /etc/ftpaccess-`date +%m%d%y` > /etc/ftpaccess
#wu-ftp#   sed "/^restricted-uid/s!restricted-uid !restricted-uid $1 !" /etc/ftpaccess-`date +%m%d%y` > /etc/ftpaccess
#wu-ftp#   echo "guest-root /home/$1/public_html $1" >> /etc/ftpaccess

   echo "7)  Add user to vsftpd chroot list
   cat `echo $1` >> /etc/vsftpd/vsftpd.chroot_list

   echo "8)  Setting Disk Quotas to default 50Mb limit:"
#  Use user johndoe as a prototype.
   edquota -p johndoe $1

   echo "9)  Admin Follow-up:"
   echo "     Modify quota.user if different than default"
   echo "     Make changes to Bind names services on dns1 and dns2 if necessary"
   echo "       Change /etc/http/conf/httpd.conf or 
   echo "       add config to /etc/http/conf.d/ if using a new domain name"
   echo "       Add e-mail aliases to mail server if necessary"

FYI: Sample robots.txt files:

Useful links and resources:

technical book image Books:

Amazon book image "Ubuntu Unleashed 2017 edition:"
Covering 16.10 and 17.04, 17.10 (12th Edition)
by Matthew Helmke, Andrew Hudson and Paul Hudson
Sams Publishing, ISBN# 0134511182

Amazon book image "Ubuntu Unleashed 2013 edition:"
Covering 12.10 and 13.04 (8th Edition)
by Matthew Helmke, Andrew Hudson and Paul Hudson
Sams Publishing, ISBN# 0672336243
(Dec 15, 2012)

Amazon book image "Ubuntu Unleashed 2012 edition:"
Covering 11.10 and 12.04 (7th Edition)
by Matthew Helmke, Andrew Hudson and Paul Hudson
Sams Publishing, ISBN# 0672335786
(Jan 16, 2012)

Amazon book image "Red Hat Enterprise Linux 7: Desktops and Administration"
by Richard Petersen
Surfing Turtle Press, ISBN# 1936280620
(Jan 13, 2017)

Amazon book image "Fedora 18 Desktop Handbook"
by Richard Petersen
Surfing Turtle Press, ISBN# 1936280639
(Mar 6, 2013)

Amazon book image "Fedora 18 Networking and Servers"
by Richard Petersen
Surfing Turtle Press, ISBN# 1936280698
(March 29, 2013)

Amazon book image "Fedora 14 Desktop Handbook"
by Richard Petersen
Surfing Turtle Press, ISBN# 1936280167
(Nov 30, 2010)

Amazon book image "Fedora 14 Administration and Security"
by Richard Petersen
Surfing Turtle Press, ISBN# 1936280221
(Jan 6, 2011)

Amazon book image "Fedora 14 Networking and Servers"
by Richard Petersen
Surfing Turtle Press, ISBN# 1936280191
(Dec 26, 2010)

Amazon book image "Practical Guide to Ubuntu Linux (Versions 8.10 and 8.04)"
by Mark Sobell
Prentice Hall PTR, ISBN# 0137003889
2 edition (January 9, 2009)

Amazon book image "Fedora 10 and Red Hat Enterprise Linux Bible"
by Christopher Negus
Wiley, ISBN# 0470413395

Amazon book image "Red Hat Fedora 6 and Enterprise Linux Bible"
by Christopher Negus
Sams, ISBN# 047008278X

Amazon book image "Fedora 7 & Red Hat Enterprise Linux: The Complete Reference"
by Richard Petersen
Sams, ISBN# 0071486429

Amazon book image "Red Hat Fedora Core 6 Unleashed"
by Paul Hudson, Andrew Hudson
Sams, ISBN# 0672329298

Amazon book image "Red Hat Linux Fedora 3 Unleashed"
by Bill Ball, Hoyt Duff
Sams, ISBN# 0672327082

Amazon book image "Red Hat Linux 9 Unleashed"
by Bill Ball, Hoyt Duff
Sams, ISBN# 0672325888
May 8, 2003

I have the Red Hat 6 version and I have found it to be very helpful. I have found it to be way more complete than the other Linux books. It is the most complete general Linux book in publication. While other books in the "Unleashed" series have dissapointed me, this book is the best out there.

Amazon book image "Apache Server Bible 2"
by Mohammed J. Kabir
ISBN # 0764548212, Hungry Minds

This book is very complete covering all aspects in detail. It is not your basic reprint of the apache.org documents like so many others.

Amazon book image "Pro DNS and Bind"
by Ronald Aitchison
Apress, ISBN# 1590594940

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