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== link:index.html[Index] -> link:config.html[Configuration]
Last checked: 2011/03/17 Cherokee 1.2.2b
Virtual Server
'Virtual Server' is an abstraction mechanism that allows you to define
a custom number of parameters and rules that have to be applied to one
or more domains.
In a Cherokee server there must be at least one virtual server named
`default`, and there is no maximum number. You can define and delete
as many as you want, with the sole exception of `default` which must
be present always.
When the server receives a request it will try to match the domain
name specified in the virtual server that should handle it. In case no
virtual server matches the request, `default` will be used.
image::media/images/admin_vserver.png[Virtual server]
This section of the admin is divided in a left panel and main contents
section on the right.
The panel displays the list of virtual servers, which can be filtered
according to the matching criteria specified in the `Virtual Server
Filtering` box, and has two buttons at the top that correspond, from
left to right, to `Add New Virtual Server` and `Clone Selected
Virtual Server`.
Whenever you select a virtual server, the main content area displays
information relevant to the chosen host.
You should be aware that the order in which the virtual servers are
listed is not arbitrary. The list is evaluated from top to bottom
whenever Cherokee receives a request, and the first virtual server
that matches the given request will be the one used to send a reply.
You can drag and drop the elements of the list to change the order in
which the matches are evaluated.
The `default` virtual server is always at the bottom and cannot be
dragged. As mentioned above, if a request doesn't match any other
virtual server, it falls through all the way to the default one to
ensure no requests are left unattended. The most simple usage
scenarios usually involve only the default virtual host, and do not
require additional virtual servers.
The entries on the `Virtual Server` list are composed of two elements:
- *Name*
An alias that is used to identify the virtual server and is the value
used when filtering the virtual servers to be listed. The domain names
handled by the virtual server should be specified later in the virtual
server details page.
- *Document Root*
This is the directory from which Cherokee will serve files. For
example, if the Document Root is `/var/www`, then a client's request
for `` refers to
`/var/www/index.html` on the server.
In the simplest case, the server might return the contents of the file
to the client. But Cherokee provides a richer mechanism of behaviors,
based on the the URL. Behaviors are described
link:#behavior[below]. For now, just know that the combination of a
URL and the Document Root specifies the match (for instance, a file on
the server), but does not specify how that file will be served. Note
that not all rules will necessarily match files to be sent to the
client, so the Document Root is not always used.
This is controlled by behavior rules. The set of rules is checked from
the highest to the lowest possible priority. Once a rule is matched,
the server appends the path from the requested URL to the document
root to make the path to the document. If it is a directory, this
information is used. If other rules apply to a parent directory, those
are applied as well without overwriting the original behavior:
---- refers to /var/www/index.html
This might seem complicated but it's actually simple to
understand. For example suppose you had a directory called /secret
that was protected with authentication, and there was also a rule with
higher priority for /secret/cgi that only specified to use the CGI
handler. Under these circumstances, if a request was received for
/secret/cgi/something then the CGI handler would be taken and it would
inherit the authentication specified for /secret.
*Add New Virtual Server* allows the creation of additional virtual
hosts, either manually or by using any of the available configuration
link:config_wizards.html[wizards]. These are configuration assistants
that will allow you to set up a new virtual server tailored to some
application's specific needs. The wizard will ask for some basic
values, such as the name of the new virtual server or anything that
might be needed to make its job, like deploying a Django application,
installing Wordpress or whatever task you might have chosen. The
wizards can also be run on a per-server basis, in which case instead
of creating a new dedicated virtual server, the required changes will
be added to the existing one. To use the wizards in this manner you
will have to trigger them from the `Behavior` panel instead of the
`Virtual Server Panel`. This `Behavior` panel is specific to a given
virtual host, and can be activated using the `Rule Management` button
of the `Behavior` tab. You can read more about automatic configuration
on the link:config_wizards.html[wizards] section. Regardless of them
being used from the `Virtual Server` panel or the `Behavior` panel,
one or more rules will be created to suit a particular scenario. The
main difference will lay on the wizard creating a new virtual server
or just customizing an existing one, depending on the instantiation
*Clone Selected Virtual Server* is simply a matter of selecting a
target name and a source virtual server currently present. Every
setting will be duplicated. From then onwards changes applied to any
of them, be it the original or the copied Virtual Servers, will only
apply to the implicated one. This is a great way to set up complex
domains, since you can use the existing ones as templates to be
refined with further work.
A detailed explanation of every tab follows.
- *Virtual Server nickname*
The name that will be used to identify the virtual server.
- *Document Root*
Path to use as root directory for the virtual server.
- *Directory Indexes*
The DirectoryIndex directive sets the list of resources to look for
when the client requests an index of the directory by specifying a /
at the end of the directory name. Several URLs may be given, in which
case the server will return the first one that it finds. If none of
the resources exist, the server will reply according to the handler
Note that the documents do not need to be relative to the directory:
would cause the CGI script /cgi-bin/ to be executed if neither
index.html nor index.txt existed in a directory.
There is a special case in which the directory index entry starts with
a slash. For example, /cgi-bin/ In that case, it will use it
as the object accessible under that public address of the same virtual
server, so it will take care about the possible configuration of the
/cgi-bin/ directory and/or the pl extension.
- *Keep-alive*
This flag is enabled by default. It is used to enable or disable
Keep-alive connections on a per-virtual-server basis. Keeping
persisting connections has dramatic effects both in speed, but very
high traffic loads can suffer because less connections are available
for any given moment.
- *Advanced Virtual Hosting*
Settings to link:config_virtual_servers_evhost.html[host many
Host Match
This section allows to define the list of domains that the virtual
server implements.
It can accept either FQDN (Fully Qualified Domain Names), wild card
entries, regular expressions, IPs/Subnets, or a combination of methods that
will be evaluated as a logical OR. This can be useful for some rare
cases where you might need to match by IP OR wildcards simultaneously,
such as the link:cookbook_ssl.html#workaround[HTTPS-without-SNI workaround]
documented in the link:cookbook.html[cookbook].
For instance::
Hint: Although it is rare, there are some web-broswsers out there that
do not seem to convert the FQDN to lowercase before sending the
requests. This mainly happens with built-in browsers or very-early
implementations. Even in those cases it is possible to have
case-insensitive host matching by using regular-expression
matching. For example, if your domain name was `` and
were dealing with one such browser, you would have to prepend *(?i)*
to your regular expression. That in turn would perform a
case-insensitive evaluation, effectively solving the problem.
The followgin Case-insensitive RegEx matches both and
Note that you should probably keep in mind the way this list is
interpreted in order to avoid future problems. Whenever Cherokee
receives a request for a specific domain, it evaluates the `Domain
list` of every defined virtual host in the order defined by the
priorities of such hosts. When it finds a match, it stops the
evaluation and starts matching the specific rules from that virtual
host to send the appropriate response.
If no domain name matches the request, Cherokee re-evaluates the list
of virtual hosts trying to match the request against the `Nicknames`,
also using the priorities defined by the virtual host order.
Only after failing both with the domain names and the nicknames will
Cherokee issue the failure, in which case the default virtual server
is used to handle the request.
IMPORTANT: It is easy to overlook the way in which virtual servers are
evaluated, which leads to the common problem of not knowing exactly
why some virtual servers work and some don't. The list of Frequently
Asked Questions includes link:other_faq.html#faq19["Why are my
nicknames not matched, while * does work?"]. A careful
reinterpretation of what has just been explained in this section
should clarify any doubts.
WARNING: Do not use the IP/Subnet host match as a security measure to
prevent access to specific IP addresses. The purpose of the IP/Subnet
match type was to implement the SSL certificate selection workaround
that other web servers have been using for years. If it were to be
attacked, it could be easily overcome by simply setting the Host
header to the name of the virtual server. To restrict the traffic of
one of your virtual servers based on the incoming IP, please read the
appropriate cookbook entry,
link:cookbook_traffic_restriction.html[restricting traffic by IP].
This sections allows to define a set of rules to define how the server
should handle the different requests. A summary of the existing rules
is presented, containing several fields of information:
. *Match*: what the rule matches, which shows information about the
web target of the rule (be it a path, a file type, etc.) plus the
rule type. You can check the complete list of rule types in the
link:config_virtual_servers_rule_types.html[Rule Types] section.
. *Handler*: The handler that manages the requests that match this
rule. Read on for further details.
. *Authentication*: Indicates if authentication is used for this
rule. This can be set up through the
link:config_virtual_servers_rule.html[Rule Entry] menu.
. *Root*: Indicates if the rule defines an alternative document root
. *Secure*: Which indicates that the rule only applies for HTTPS
. *Encoders*: Indicates if any encoding is applied to the rule.
. *Expiration*: Indicates if expiration headers are configured for the rule.
. *Timeout*: Indicates if there is a defined connection timeout for
the rule.
. *Shaping*: Whether traffic shaping is enabled.
. *Logging*: Whether the rule matches are logged or not.
. *Final*: If this flag is present it means that no other rules will
be applied after this one, even if the request also matches other
rules with lower priority.
. *Enabled*: If the rule is currently enabled or not, which might
completely alter the behavior of the virtual server.
These rules can be defined based on the directory that the request
targets, the extension of the file that it is requesting, or a regular
expression that may match the request among other options.
It is very important to know that these rules are prioritized. The
higher its priority is, the sooner they are checked. You could think
of a network routing table, it is quite similar. You can set the
relative priorities among the rules from within the `Behavior` panel,
which is accessed through the `Rule Management` button. This button
will switch the left panel from `Virtual Server` mode to `Rule mode`,
and the list of virtual servers on the left panel will be replaced by
a panel with the list of rules.
In `Rule mode` you wiil be able to define a set of rules to define how
the server should handle the different requests, and simply dragging
and dropping the rules in the desired position will do. If you click
on the rule name, the rule's configuration options will be displayed
in the main content area. If you click anywhere else, you will be able
to drag and drop it into the desired position).
image::media/images/admin_behavior.png[Virtual server]
Each of these behavior rules must specify the handler that the server
should use to reply to the requests that match the rule.
The selection of any one of the rule targets will offer new
configuration options through the
link:config_virtual_servers_rule.html[Rule Entry] menu.
Each of the mentioned handlers can be fine-tuned through that
menu. Refer to each handler's documentation if you are interested in
the available settings.
These rules can also be combined with boolean operators, so you can
apply AND to require two rules, NOT to negate and so forth. These can
be nested as much as necessary.
It is quite easy to fully specify a virtual server's behavior having
just some notions of Cherokee's way of working. However, there might
be some corner cases where Cherokee will behave in a manner that could
not seem obvious at first. Every doubt can be easily cleared by simple
understanding in full detail the way a rule is applied. For instance
lets suppose there is an `Extension` type rule configured to handle
PHP files. If a request is made for
``, this rule *WOULD NOT* be
applied at first because the request doesn't end with the appropriate
extension: it has some additional path information. However, if there
is a `Default` rule configured that is managed by the `List and Send`
handler, things would work. This is because the `Default` rule would
catch any unmatched requests, and the `List and Send` handler would
notice the PATHINFO part of the request. It would then split the
request in two parts, separating the PHP file from the appended
information, and would then evaluate once more the list of rules. This
time the request would end in `.php` and thus it would match the
`Extension` rule meant to handle PHP files.
Personal Webs
This options allows to setup the name of a subdirectory inside the
users' home directory that will be used as document root for personal
web content. For instance, if `/foo` was specified, a user `bar` could
publish the content of ~/foo at the relative URL /~bar
This option is disabled if the 'Directory name' field is empty.
Error Handler
Several mechanisms exist to handle errors.
. Default errors
. Custom redirections
. Closest match
Using the 'Custom redirections' error handler we can easily redirect
errors to a custom path or website.
image::media/images/admin_vserver_errors.png[Virtual server]
In this case, the handled errors will be redirected to the specified
resource, while non-defined errors will trigger an HTTP 500 error. In
case this is not the desired behavior, you can set a `Default Error`
to catch and redirect the non-defined ones.
The 'Closest match' error handler should never fail to deliver
something. If a requested resource is not available, the closest match
will be sent. The only exception to this is when nothing at all is at
Cherokee's disposal, in which case a standard http error is sent.
The link:modules_loggers.html[loggers] are a type of Cherokee modules
to write the server log information using different destinations
and/or formats:
* Destination: File, syslog, program execution and standard error output.
* Format: Combined (Apache compatible), NCSA or custom.
If a virtual server doesn't have a logger set up it will not log anything.
image::media/images/admin_vserver_loggers.png[Virtual server]
By default Cherokee ships three loggers implementing three different
logging formats:
- combined - link:modules_loggers_combined.html[Combined Log Format]
Logging using the Apache log format. It is the `de facto standard` nowadays.
- ncsa - link:modules_loggers_ncsa.html[NCSA Log Format]
Logging using the NCSA log format.
- custom - link:modules_loggers_custom.html[Customizable Log Format]
Logging using a user-specified format.
Besides, this sections allows you to specify several other options,
such as the backend used to store errors.
The virtual server must be configured with the path to the certificate
before using secure connections (https). There is a document which
might help to generate SSL link:cookbook_ssl.html[keys] and that
should provide tips and information on how to configure SSL, TLS and
Cherokee fully supports the usage of different certificates for each
virtual server in a given host by using SNI as defined in
link:[RFC 3546].
If you want HTTPS to work, you must remember this:
. Providing the PEM-encoded files is mandatory for both `Certificate`
and `Certificate key` fields. Providing the `CA List` and the
`Client Certs` is optional. The trusted CA certificates file should
be a single file with all the certificates concatenated. The `Client
Certs`, also PEM-encoded, is used to check the client
certificates. You can read more about
link:cookbook_ssl.html#ssl-support[enabling SSL support] on the
SSL/TLS section of the documentation.
. If you have several virtual servers, the `Security` section must be
configured for the `default` virtual server besides any other
virtual server you want to support HTTPS. This makes sense, since by
enabling the feature in any one of them you are opening the HTTPS
port in your host, and receiving HTTPS requests for a virtual server
that does not provide the service can not be handled correctly.
This situation can be dealt with in several ways, none of which are
really elegant in design: falling back to HTTP, issuing an error
that is likely to restart the HTTPS handshake, etc. The approach
taken by Cherokee is at least coherent, folding back to the
`default` virtual server. Of course, to do so it needs correct
`Security` settings to provide an HTTPS stream, as has just been
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