Virtual Web mini-HOWTO
Dan Pancamo
Parag Mehta
pm@gnuos.org
David Merrill - Conversion from text to DocBook SGML.
Revision History
Revision 1.1 2001-06-03
New maintainer, converted to DocBook (SGML), Licensed under GFDL.
Revision 1.0 1995-11-24
Initial Release.
This HOWTO discuss the essentials of setting up a Virtual Web Site under
Linux.
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Table of Contents
1. License
2. What is a Virtual Web Site?
3. What Software and Software Patches Do I Need?
3.1. Linux Kernel
3.2. HTTP Servers
4. How Do I set it up?
4.1. Create the New Account
4.2. NCSA 1.5 or Apache Config Files
4.3. Configuring the interface
4.4. Registering with Internic
4.5. Configuring Named
4.5.1. Example /etc/named.boot
4.5.2. Example /etc/named.data/db.domain1.com
4.5.3. Example /etc/named.data/db.xxx.xxx.xxx
4.5.4. Restart named
4.6. Virtual Mail
4.6.1. Sendmail Configuration
4.7. Virtual FTP
5. Links to More Virtual Web Information
1. License
This document is made available under the GNU Free Documentation License.
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2. What is a Virtual Web Site?
A World Wide Web (WWW) Server is normally a single machine dedicated to
processing HTTP requests for a single WWW site. Simply put, one WWW site per
machine. Since the computing resources for processing httpd requests is low
for most WWW sites, the majority of the computing resources are left unused.
A virtual WWW site simple allows more than one WWW site to share a single
processor. Instead of having www.domain1.com and www.domain2.com requiring
two physical computing devices, www.domain1.com and www.domain2.com can be
located on a single computing device and share common resources.
Normally small computing facilities, and small businesses do not have the
resources to maintain a dedicated web server and a dedicated Internet
connection. These cost can easily start off at $10K for setup, and $500-2500
monthly to maintain. Small computing facilities, and small businesses are now
able to "rent" WWW space from a Virtual WWW providers. The customer can then
maintain the WWW "pages" using a local telnet and/or FTP connection.
WWW providers such as InfoCom Networks http://www.infocom.net/ provide WWW
space as low as $75 per month. A few Virtual Sites might clear up the
mystery. So the cost of setting up a WWW site is significantly lower than
that of setting up a dedicated server and connection. The Virtual Site has a
major advantage over other WWW addressing schemes such as
"www.yourprovider.com/~businessname". The Virtual WWW server inherently
contains the ability to move to a new location or setup a dedicated WWW
server without changing addresses. Changing WWW URL's can result in a major
loss of traffic to your site, and lots of business literature updates.
With most web sites, www.domain1.com and www.domain2.com both resolve to
separate IP's. In order to accept multiple request from a single host, the
virtual host must be able to answer request for both sites. The method used
to solve this problem is called IP aliasing. IP aliasing allows a single host
to accept request for multiple IP's. The virtual Web server must have the
ability to alias IP's
IP aliasing is just one part of the virtual solution. The Domain Name System
(DNS) also must be configured to resolve both www.domain1.com and
www.domain2.com. If domain1.com and domain2.com are new domains, then both
must be registered with Internic. Currently, Internic is charging $50 a year
to maintain your domain.
Most virtual WWW sites should also provide virtual mail, or the ability to
forward all mail to the virtual domain to another user or users.
Virtual FTP or the ability to FTP using the standard host name
"ftp.domain1.com" should also be configured by the WWW provider.
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3. What Software and Software Patches Do I Need?
3.1. Linux Kernel
Linux versions 1.2.X requires the IPalias patch alias-patch-1.2.1-v1 and
alias-net-tools.tar. I'm not sure if 1.3.X supports this patch yet. For more
information on the IPalias patch see ftp://ftp.mindspring.com/users/rsanders/
ipalias/
Using multiple dummy interfaces has been suggested in place of the IPalias
solution. While the dummy solution may work, it does not appear to be as
clean as the IPalias solution. For more information on using Apache and the
dummy solution see Aram Mirzadeh's virtual hosting information at http://
www.qosina.com/apache/virtual.html
All that is required to add a new alias using the IPalias method is: > /sbin/
ifconfig eth0 alias www.domainX.com
Also, the IPalias solution is supported on several other platforms.
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3.2. HTTP Servers
NCSA 1.5, Apache, and Spinner support Virtual hosting. http://
hoohoo.ncsa.uiuc.edu/docs/Overview.html http://www.apache.org/ http://
spinner.infovav.se/
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4. How Do I set it up?
4.1. Create the New Account
Create a regular Linux account for the virtual customer with home directory
and mail.
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4.2. NCSA 1.5 or Apache Config Files
Virtual Host implementations are still changing. A few patches exist to
support Virtual Host Check the server's release notes for more details. NCSA
1.5 or Apache now include the Virtual patches, and I have been told that
Spinner supports virtual hosts.
One virtual patch supports the following srm.conf syntax, however the second
NCSA 1.5 method of defining a Virtual host allows for greater flexibility
SubDocumentRoot www.domain1.com /usr/local/etc/httpd/docs/domain1
SubDocumentRoot www.domain2.com /usr/local/etc/httpd/docs/domain2
NCSA and Apache support the following httpd.conf syntax:
ServerAdmin webmaster@domain1.com
DocumentRoot /usr/local/etc/httpda/docs/domain1
ServerName www.domain1.com
ErrorLog logs/errors.domain1.com
TransferLog logs/access_log.domain1.com
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4.3. Configuring the interface
Once the IPalias patches have been installed add the following to your /etc/
rc.d/rc.local on your local web server.
/sbin/ifconfig eth0 alias www.domain1.com
/sbin/ifconfig eth0 alias www.domain2.com
/sbin/ifconfig eth0 alias www.domainN.com
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4.4. Registering with Internic
If you are setting up a new domain or change a current domain, you must
register the domain with Internic. The template can be found at ftp://
rs.internic.net/templates/domain-template.txt
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4.5. Configuring Named
Named will need to be configured so that your virtual domain will be visible
to the outside world. I don't claim to be an expert on DNS. Suggestions
always welcome.
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4.5.1. Example /etc/named.boot
directory /etc/named.data
primary realdomain.com db.realdomain.com
primary xxx.xxx.xxx.IN-ADDR.ARPA db.xxx.xxx.xxx
primary 0.0.127.IN-ADDR.ARPA db.local
primary domain1.com db.domain1.com
primary domain2.com db.domain2.com
cache . named.root
Note Replace x with your IP.
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4.5.2. Example /etc/named.data/db.domain1.com
$ORIGIN com.
domain1 IN SOA domain1.com. hostmaster.domain1.com. (
10134 43200 3600 604800 86400 )
IN NS ns1.realdomain.com.
IN MX 10 mail.realdomain.com.
IN MX 0 domain1.com.
domain1.com. IN A xxx.xxx.xxx.xxx ;www.domain1.com IP
$ORIGIN domain1.com.
ftp IN CNAME domain1.com.
www IN CNAME domain1.com.
mail IN CNAME domain1.com.
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4.5.3. Example /etc/named.data/db.xxx.xxx.xxx
You should already have a db.xxx.xxx.xxx for your current site update it to
contain the new virtual domains for reverse lookups
xx IN PTR www.domain1.com.
xx IN PTR www.domain2.com.
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4.5.4. Restart named
Once you've finished editing config files, you will need to restart the named
daemon.
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4.6. Virtual Mail
Your virtual customers will more than likely want the ability to have mail
that is sent to their domain forwarded to another domain. A few sendmail.cf
changes will do the trick. After several months of trying different sendmail
changes, this is the 1st method that I found that works and requires only one
sendmail.cf change for each new virtual site.
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4.6.1. Sendmail Configuration
1. Retrieve the current version of sendmail that contains makemap btree
support.
2. Create a file called /etc/domainalias with the following mappings:
*@domain1.com localnet@realdomain.com
*@domain2.com townplaz@realdomain.com
*@domainN.com soracomp@realdomain.net
webmaster@domain1.com somuser@anotherhost.com
jamison@domain2.com anotheruser@somehost.com
3. Create the maped DB file
+---------------------------------------------------------------+
|makemap btree /etc/domainalias.db < /etc/domainalias |
+---------------------------------------------------------------+
4. /etc/sendmail.cf changes:
a. Add a Cw record for each new virtual host
Cwdomain1.com
Cwdomain2.com
b. Add the domainalias mapping only once.
Kdomainalias btree /etc/domainalias.db
c. Add/Change Ruleset 98
###################################################################
### Ruleset 98 -- local part of ruleset zero (can be null) ###
###################################################################
S98
R$+ < $+ . > $1 < $2 > remove trailing dots
R$+ < $+ > $: < > $(domainalias $1$2 $) match user@address
R< > $+ @ $* $: < $1 > $(domainalias * @ $2 $) match *@address
R< $+ > * $* $: < > $1 $2 replace * with userid
R < $+ > $+ $: < > $2 bugfix
R< > $* $: $>3 $1 and rewrite using S3
5. Sendmail Testing
Test the sendmail configuration to verify the new sendmail.cf changes
sendmail -v -bv info@domain1.com
The final destination should be displayed.
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4.7. Virtual FTP
Currently, I have not been able to get Virtual FTP to work. A few patches
exist, and I'm sure a working patch exist. We just create a working directory
/home/ftp/business/domain1, but a true Virtual FTP would be nice.
If anyone would like to contribute a solution, I would be more than happy to
add it here.
Arnt Gulbrandsen has rewritten ftpd and has included support for independent
FTP services The Troll Tech FTP Daemon
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5. Links to More Virtual Web Information
http://hoohoo.ncsa.uiuc.edu/docs/Overview.html
http://www.apache.org/
http://www.qosina.com/apache/virtual.html
http://spinner.infovav.se/
ftp://ftp.mindspring.com/users/rsanders/ipalias/
http://www.thesphere.com/~dlp/TwoServers/
http://hoohoo.ncsa.uiuc.edu/docs/setup/httpd/VirtualHost.html
ftp://ftp.dhp.com:/pub/linux/virtual-hosting
