Apache Karaf is a small OSGi based runtime which provides a lightweight container onto which various components and applications can be deployed.

Here is a short list of features supported by the Karaf:

• Hot deployment: Karaf supports hot deployment of OSGi bundles by monitoring jar files inside the [home]/deploy directory. Each time a jar is copied in this folder, it will be installed inside the runtime. You can then update or delete it and changes will be handled automatically. In addition, the Karaf also supports exploded bundles and custom deployers (blueprint and spring ones are included by default).
• Dynamic configuration: Services are usually configured through the ConfigurationAdmin OSGi service. Such configuration can be defined in Karaf using property files inside the [home]/etc directory. These configurations are monitored and changes on the properties files will be propagated to the services.
• Logging System: using a centralized logging back end supported by Log4J, Karaf supports a number of different APIs (JDK 1.4, JCL, SLF4J, Avalon, Tomcat, OSGi)
• Provisioning: Provisioning of libraries or applications can be done through a number of different ways, by which they will be downloaded locally, installed and started.
• Native OS integration: Karaf can be integrated into your own Operating System as a service so that the lifecycle will be bound to your Operating System.
• Extensible Shell console: Karaf features a nice text console where you can manage the services, install new applications or libraries and manage their state. This shell is easily extensible by deploying new commands dynamically along with new features or applications.
• Remote access: use any SSH client to connect to Karaf and issue commands in the console
• Security framework based on JAAS
• Managing instances: Karaf provides simple commands for managing multiple instances. You can easily create, delete, start and stop instances of Karaf through the console.
• Supports the latest OSGi 4.2 containers: Apache Felix Framework 3.0 and Eclipse Equinox 3.6

If you are in a hurry to have Apache Karaf up and running right away, this section will provide you with some basic steps for downloading, building (when needed) and running the server in no time. This is clearly not a complete guide so you may want to check other sections of this guide for further information.

All you need is 5 to 10 minutes and to follow these basic steps.

Apache Karaf is a small and lightweight OSGi based runtime. This provides a small lightweight container onto which various bundles can be deployed.

Apache Karaf started life as the Apache ServiceMix kernel and then moved as a Apache Felix subproject. Don't be surprised by any transitional references which remain.

At this time you have one option to get the software. The fastest and easiest way is to get the binary directly from the Apache site. Since this article is intended to help you to have Apache Karaf up and running in the fastest way only the binary download will be covered at this time.

Although this installation path is the fastest one, still you will need to install some software before installing Karaf.

Depending on the platform you plan to install and run Karaf you will select the appropriate installation image. Open a Web browser and access the following URL, there you will find the available packages for download (binaries and source code).

With Karaf already installed, open a command line console and change directory to <KARAF_HOME>. To start the server, run the following command in Windows:

bin\karaf.bat

respectively on Unix:

bin/karaf

You should see the following informations on the command line console:

        __ __                  ____      
       / //_/____ __________ _/ __/      
      / ,<  / __ `/ ___/ __ `/ /_        
     / /| |/ /_/ / /  / /_/ / __/        
    /_/ |_|\__,_/_/   \__,_/_/         

  Apache Felix Karaf (2.1.2)

Hit '<tab>' for a list of available commands
and '[cmd] --help' for help on a specific command.

karaf@root> 

You can now run your first command. Simply type the <tab> key in the console.

karaf@root> 

admin:change-port         admin:connect             admin:create              admin:destroy
admin:list                admin:start               admin:stop                config:cancel
config:edit               config:list               config:propappend         config:propdel
config:proplist           config:propset            config:update             dev:dynamic-import
dev:framework             dev:print-stack-traces    dev:show-tree             features:addUrl
features:info             features:install          features:list             features:listUrl
features:refreshUrl       features:removeUrl        features:uninstall        log:display
log:display-exception     log:get                   log:set                   osgi:bundle-level
osgi:headers              osgi:install              osgi:list                 osgi:ls
osgi:refresh              osgi:resolve              osgi:restart              osgi:shutdown
osgi:start                osgi:start-level          osgi:stop                 osgi:uninstall
osgi:update               packages:exports          packages:imports          shell:cat
shell:clear               shell:each                shell:echo                shell:exec
shell:grep                shell:history             shell:if                  shell:info
shell:java                shell:logout              shell:new                 shell:printf
shell:sleep               shell:sort                shell:tac                 ssh:ssh
ssh:sshd                  cat                       clear                     each
echo                      exec                      grep                      history
if                        info                      java                      logout
new                       printf                    sleep                     sort
tac                       bundle-level              headers                   install
list                      ls                        refresh                   resolve
restart                   shutdown                  start                     start-level
stop                      uninstall                 update
karaf@root> 

You can then grab more specific help for a given command using the --help option for this command:

karaf@root> admin:create --help
DESCRIPTION
	admin:create

	Create a new instance.

SYNTAX
	admin:create [options] name

ARGUMENTS
        name
                The name of the new container instance

OPTIONS
        --help
                Display this help message
        -f, --feature
                Initial features. This option can be specified multiple times to enable multiple initial 
                features
        -p, --port
                Port number for remote shell connection
        -l, --location
                Location of the new container instance in the file system
        -furl, --featureURL
                Additional feature descriptor URLs. This option can be specified multiple times to add 
                multiple URLs

karaf@root> 

While you will learn in the remainder of this guide how to use and leverage Apache Karaf, we will just use the pre-built packaging for now.

In the console, run the following commands:

features:addurl mvn:org.apache.camel/camel-example-osgi/2.5.0/xml/features
features:install camel-example-osgi

To stop this demo, run the following command:

features:uninstall camel-example-osgi

1. Launching Karaf can result in a deadlock in Felix during module dependency resolution. This is often a result of sending a SIGINT (control-C) to the process when it will not cleanly exit. This can corrupt the caches and cause startup problems in the very next launch. It is fixed by emptying the component cache:

   rm -rf data/cache/*
   

To stop Karaf from the console, enter ^D in the console:

^D

Alternatively, you can also run the following command:

osgi:shutdown

If you are in a hurry to have Apache Karaf up and running right away, this section will provide you with some basic steps for checking out, building and running the server in no time. This is clearly not a complete guide so you may want to check other sections of this guide for further information.

All you need is 15 minutes and to follow these basic steps.

Apache Karaf is a small and lightweight OSGi based runtime. This provides a small lightweight container onto which various bundles can be deployed.

Apache Felix Karaf started life as the Apache ServiceMix kernel and then moved as a Apache Felix subproject. Don't be surprised by any transitional references which remain.

This document describes how to build the server from the latest Karaf source.

Although this installation path is the fastest one, still you will need to install some software before installing Karaf.

Change directory to the top level of the source checkout. Build Karaf using Maven as follows:

$ mvn -Pfastinstall

Distributions will be created in assembly/target. Select the file compression format compatible with your system (apache-karaf-2.0.0.zip for windows, apache-karaf-2.0.0.tar.gz for unixes) and expand the binary in a new directory; for example in z:\karaf - from now on this directory will be referenced as <KARAF_HOME>. Please remember the restrictions concerning illegal characters in Java paths, e.g. !, % etc.

The installation of Karaf is as simple as uncompressing the .zip or .tar files. The next step is to start the server.

To generate Eclipse projects for all modules, in KARAF_HOME type: mvn -Psetup.eclipse Then add each module location, prefixing each name with org.apache.karaf (for example org.apache.karaf.shell.core)

With Karaf already installed, open a command line console and change directory to <KARAF_HOME>. To start the server, run the following command in Windows:

bin\karaf.bat

respectively on Unix:

bin/karaf

You should see the following informations on the command line console:

        __ __                  ____      
       / //_/____ __________ _/ __/      
      / ,<  / __ `/ ___/ __ `/ /_        
     / /| |/ /_/ / /  / /_/ / __/        
    /_/ |_|\__,_/_/   \__,_/_/         

  Apache Felix Karaf (2.1.2)

Hit '<tab>' for a list of available commands
and '[cmd] --help' for help on a specific command.

karaf@root> 

You can now run your first command. Simply type the <tab> key in the console.

karaf@root> 

admin:change-port         admin:connect             admin:create              admin:destroy
admin:list                admin:start               admin:stop                config:cancel
config:edit               config:list               config:propappend         config:propdel
config:proplist           config:propset            config:update             dev:dynamic-import
dev:framework             dev:print-stack-traces    dev:show-tree             features:addUrl
features:info             features:install          features:list             features:listUrl
features:refreshUrl       features:removeUrl        features:uninstall        log:display
log:display-exception     log:get                   log:set                   osgi:bundle-level
osgi:headers              osgi:install              osgi:list                 osgi:ls
osgi:refresh              osgi:resolve              osgi:restart              osgi:shutdown
osgi:start                osgi:start-level          osgi:stop                 osgi:uninstall
osgi:update               packages:exports          packages:imports          shell:cat
shell:clear               shell:each                shell:echo                shell:exec
shell:grep                shell:history             shell:if                  shell:info
shell:java                shell:logout              shell:new                 shell:printf
shell:sleep               shell:sort                shell:tac                 ssh:ssh
ssh:sshd                  cat                       clear                     each
echo                      exec                      grep                      history
if                        info                      java                      logout
new                       printf                    sleep                     sort
tac                       bundle-level              headers                   install
list                      ls                        refresh                   resolve
restart                   shutdown                  start                     start-level
stop                      uninstall                 update
karaf@root> 

While you will learn in the remainder of this guide how to use and leverage Apache Felix Karaf, we will just use the pre-built packaging for now.

In the console, run the following commands:

features:install spring-dm
osgi:install -s mvn:org.apache.geronimo.specs/geronimo-activation_1.1_spec/1.0.2
osgi:install -s mvn:org.apache.servicemix.specs/org.apache.servicemix.specs.stax-api-1.0/1.1.0
osgi:install -s mvn:org.apache.servicemix.specs/org.apache.servicemix.specs.jaxb-api-2.1/1.1.0
osgi:install -s mvn:org.apache.servicemix.bundles/org.apache.servicemix.bundles.jaxb-impl/2.1.6_1
osgi:install -s mvn:org.apache.camel/camel-core/1.4.0
osgi:install -s mvn:org.springframework/spring-tx/2.5.6.SEC01
osgi:install -s mvn:org.apache.camel/camel-spring/1.4.0
osgi:install -s mvn:org.apache.camel/camel-osgi/1.4.0
osgi:install -s mvn:org.apache.camel/camel-example-osgi/1.4.0

This commands will download, install and start the specified jars.

To stop this demo, run the following command:

osgi:list | grep example

In the output, locate the line containing camel-example-osgi and note the id of the bundle in the first column. Then launch the following command:

osgi:stop [id]

If you wish, you can start again the sample by using the following command:

osgi:start [id]

To uninstall the demo, run the following command:

osgi:uninstall [id]

1. Launching SMX4 can result in a deadlock in Felix during module dependency resolution. This is often a result of sending a SIGINT (control-C) to the process when it will not cleanly exit. This can corrupt the caches and cause startup problems in the very next launch. It is fixed by emptying the component cache:

   rm -rf data/cache/*
   

To stop Karaf from the console, enter ^D in the console:

^D

Alternatively, you can also run the following command:

osgi:shutdown

This document describes how to install and configure Apache Karaf for both Unix and Windows' platforms.
Here you will find information about what are pre requisite software, where to download Karaf from and how to customize the installation to use custom ports other than the defaults.

This article contains the following sections:

Hardware:

• 5 MB of free disk space for the Apache Karaf x.y binary distribution.
• 3 MB of free disk space for the Apache Karaf x.y source distributions or SVN checkout. The Maven build requires roughly 57 MB disk space and for the dependencies Maven downloads during building further 76 MB are required. As a lot of small files are produced, the exact space demands depend greatly on your cluster utilization ratio.

Operating Systems:

• Windows: Windows XP SP2, Windows 2000.
• Unix: Ubuntu Linux, Powerdog Linux, MacOS, AIX, HP-UX, Solaris, any Unix platform that supports Java.

Environment:

This section of the Getting Started guide explains how to install binary and source distributions of Karaf on a Windows system.

Handy Hint In case you have to install Karaf into a very deep path or a path containing illegal characters for Java paths, e.g. !, % etc., you may add a bat file to start -> startup that executes subst S: "C:\your very % problematic path!\KARAF" so your Karaf root directory is S: — which works for sure and is short to type.

This procedure explains how to download and install the binary distribution on a Windows system.

This procedure explains how to download and install the source distribution on a Windows system. NOTE: Karaf requires Java 5 is compile, build and run.

This procedure explains how to download and install the binary distribution on a Unix system.

From a console window, change to the installation directory and run Karaf. For the binary distribution, go to

cd [karaf_install_dir]

and for the source distribution go to the target directory, for example:

cd [karaf_install_dir]\src\assembly\target\apache-karaf-x.y-SNAPSHOT

where karaf_install_dir is the directory in which Karaf was installed, e.g., c:\Program Files\apache-karaf-x.y.

Then type:

bin\karaf.bat

Note: Working directories get created relative to the current directory. For the working directories to be created in the proper place, Karaf must be launched from its home/installation directory.

It will start a Karaf console, allowing you to administrate your Karaf instance.

You can launch Karaf in server mode (without terminal output):

bin\start.bat

From a command shell, change to the installation directory and run Karaf. For the binary distribution, go to

cd [karaf_install_dir]

and for the source distribution go to the target directory, for example:

cd [karaf_install_dir]/src/assembly/target/apache-karaf-x.y

where karaf_install_dir is the directory in which Karaf was installed, e.g., /usr/local/apache-karaf-x.y.

Then type:

bin/karaf

Warning Do NOT close the console or shell in which Karaf was started, as that will terminate Karaf (unless Karaf was started with nohup).

If Karaf is up and running without problems, the Window's console window or the Unix command shell will display something similar to the following log line:

        __ __                  ____      
       / //_/____ __________ _/ __/      
      / ,<  / __ `/ ___/ __ `/ /_        
     / /| |/ /_/ / /  / /_/ / __/        
    /_/ |_|\__,_/_/   \__,_/_/         

  Apache Felix Karaf (2.1.2)

Hit '<tab>' for a list of available commands
and '[cmd] --help' for help on a specific command.

karaf@root> 

You can use the client mode to connect to a running Karaf:
On Windows:

bin\client.bat

On Unix:

bin/client

For both Windows and Unix installations, you can perform a clean shutdown of Karaf by using the following command:

osgi:shutdown

You can use the stop script too:
On Windows:

bin\stop.bat

On Unix:

bin/stop

Karaf provides a powerful console and a set of commands that can be used to perform various tasks. Commands can be located in the root shell or in a sub-shell. A sub-shell is a group of related commands, like commands related to the OSGi framework or the log system.

The log shell contains a few commands to display the log entries, retrieve or change the log levels:

The OSGi sub-shell provides commands for managing the OSGi framework: listing OSGi bundles, services, managing bundle lifecycles.
Look at the online help (launch osgi help command) for more informations.

Examples:

cat mvn:org.apache.servicemix/servicemix/3.2.1/pom

or

log:display | grep error

Note that this feature is not installed by default. To install it, you must run the following command:

karaf@root:/> features:install wrapper

The remote console feature allows to connect to a running Karaf instance from a remote computer and perform all the operations that are usually accessible from the local console.

The Karaf shell scripts supports a number of options to control the remote console:

• console: launch Karaf in the default mode (both local and remote console activated). This is the default mode
• server: launch Karaf in with a remote console but no local console
• client: launch Karaf in with a local console only

These options affect two system properties that can be set if you don't use the standard shell scripts:

• karaf.startLocalConsole
• karaf.startRemoteShell

It is also possible to use a more lightweight way to connect to a Karaf instance using the following command line:

java -jar lib/karaf-client.jar

There are a few parameters that can be set on the command line to change the URL used to connect to Karaf, the user or the password.
All these parameters are detailed in the help screen:

> java -jar lib/karaf-client.jar --help
Apache Karaf client
  -a [port]     specify the port to connect to
  -h [host]     specify the host to connect to
  -u [user]     specify the user name
  -p [password] specify the password
  --help        shows this help message
  -v            raise verbosity
  -r [attempts] retry connection establishment (up to attempts times)
  -d [delay]    intra-retry delay (defaults to 2 seconds)
  [commands]    commands to run
If no commands are specified, the client will be put in an interactive mode

For example, to shut down Karaf from the command line, you can run the following command:

> java -jar lib/karaf-client.jar 
smx@root:/> osgi:shutdown
smx@root:/>
>

The client jar also supports passing command line arguments to the remote Karaf.

> java -jar lib/karaf-client.jar osgi:shutdown
>

You can use any standard SSH client to connect to a Karaf instance. The default port is 8101.

> ssh -p 8101 -l karaf localhost
karaf@localhost's password: karaf
karaf@root:/>

First, open a terminal and launch Karaf in server mode (you could use a Karaf instance in console mode too):

bin/karaf server

On another terminal, start another Karaf instance in client mode:

bin/karaf client

User another Karaf instance to start the client At this point in time, you can not use the same Karaf installation to start both the server and the client, so you need to create a new instance using the 'admin create xxx' command and use that one to start the client. If you are on a different host or already use another copy of Karaf, this requirement does not hold.

Once the console appears, you can run the remote rsh command to connect to the other Kernel:

ssh:ssh -l karaf -P karaf -p 8101 localhost 

To verify that your are connected to the remote instance, run the following command:

info

and check the system informations.

The TCP port is configured at the following location:

[KARAF]/etc/org.apache.karaf.shell.cfg

The defaut configuration is as below:

sshPort=8102
sshHost=0.0.0.0
sshRealm=karaf
hostKey=${karaf.base}/etc/host.key

The port used can easily be changed by changing the default port 8101 in the sshPort property.

The log subshell comes with 3 commands:

• log:display: display the last log entries
• log:display-exception: display the last exception from the log
• log:get: show the log levels
• log:set: set the log levels

For example, if you want to debug something, you might want to run the following commands:

> log:set DEBUG
... do something ...
> log:display

The following picture describes the architecture of the deployer.

Karaf includes a deployer that is able to deploy plain blueprint or spring-dm configuration files.
The deployer will transform on the fly any spring configuration file dropped into the deploy folder into a valid OSGi bundle.

The generated OSGi manifest will contain the following headers:

Manifest-Version: 2
Bundle-SymbolicName: [name of the file]
Bundle-Version: [version of the file]
Spring-Context: *;publish-context:=false;create-asynchronously:=true
Import-Package: [required packages]
DynamicImport-Package: *

The name and version of the file are extracted using a heuristic that will match common patterns. For example my-config-1.0.1.xml will lead to name = my-config and version = 1.0.1.
The default imported packages are extracted from the spring file definition and includes all classes referenced directly.

If you need to customize the generated manifest, you can do so by including an xml element in your spring configuration:

<spring:beans ...>
  <manifest>
    Require-Bundle= my-bundle
  </manifest>

To be able to hot deploy features from the deploy folder, you can just drop a feature descriptor on that folder. A bundle will be created and its installation (automatic) will trigger the installation of all features contained in the descriptor. Removing the file from the deploy folder will uninstall the features.
If you want to install a single feature, you can do so by writing a feature descriptor like the following:

<features>
  <repository>mvn:org.apache.servicemix.nmr/apache-servicemix-nmr/1.0.0/xml/features</repository>
  <feature name="nmr-only">
    <feature>nmr</feature>
  </feature>
</features>

This feature allow the deployment at runtime of JAAS based configuration for use in various parts of the application. This includes the remote console login, which uses the karaf realm, but which is configured with a dummy login module by default. These realms can also be used by the NMR, JBI components or the JMX server to authenticate users logging in or sending messages into the bus.

In addition to JAAS realms, you can also deploy keystores and truststores to secure the remote shell console, setting up HTTPS connectors or using certificates for WS-Security.

A very simple XML schema for spring has been defined, allowing the deployment of a new realm or a new keystore very easily.

To deploy a new realm, you can use the following XSD which is supported by a Spring namespace handler and can thus be defined in a spring xml configuration file.

<xs:schema elementFormDefault='qualified'
           targetNamespace='http://karaf.apache.org/xmlns/jaas/v1.0.0'
           xmlns:xs='http://www.w3.org/2001/XMLSchema'
           xmlns:bp="http://www.osgi.org/xmlns/blueprint/v1.0.0"
           xmlns:tns='http://karaf.apache.org/xmlns/jaas/v1.0.0'>

    <xs:import namespace="http://www.osgi.org/xmlns/blueprint/v1.0.0"/>

    <xs:element name="config">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="module" minOccurs="0" maxOccurs="unbounded">
                    <xs:complexType mixed="true">
                        <xs:attribute name="className" use="required" type="xs:string" />
                        <xs:attribute name="flags" default="required">
                            <xs:simpleType>
                                <xs:restriction base="xs:NMTOKEN">
                                    <xs:enumeration value="required"/>
                                    <xs:enumeration value="requisite"/>
                                    <xs:enumeration value="sufficient"/>
                                    <xs:enumeration value="optional"/>
                                </xs:restriction>
                            </xs:simpleType>
                        </xs:attribute>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
            <xs:attribute name="name" use="required" type="xs:string" />
            <xs:attribute name="rank" use="optional" default="0" type="xs:int" />
        </xs:complexType>
    </xs:element>

    <xs:element name="keystore">
        <xs:complexType>
            <xs:attribute name="name" use="required" type="xs:string" />
            <xs:attribute name="rank" use="optional" default="0" type="xs:int" />
            <xs:attribute name="path" use="required" type="xs:string" />
            <xs:attribute name="keystorePassword" use="optional" type="xs:string" />
            <xs:attribute name="keyPasswords" use="optional" type="xs:string" />
        </xs:complexType>
    </xs:element>
    
</xs:schema>

Karaf provides a simple, yet flexible, way to provision applications or "features". Such a mechanism is mainly provided by a set of commands available in the features shell. The provisioning system uses xml "repositories" that define a set of features.

The following commands can be used to manage the list of descriptors known by Karaf. They use URLs pointing to features descriptors. These URLs can use any protocol known to the Apache Karaf, the most common ones being http, file and mvn.

features:addUrl      Add a list of repository URLs to the features service
features:removeUrl   Remove a list of repository URLs from the features service
features:listUrl     Display the repository URLs currently associated with the features service.
features:refreshUrl  Reload the repositories to obtain a fresh list of features

Karaf maintains a persistent list of these repositories so that if you add one URL and restart Karaf, the features will still be available.

The refreshUrl command is mostly used when developing features descriptors: when changing the descriptor, it can be handy to reload it in the Kernel without having to restart it or to remove then add again this URL.

If you know some more URLs feel free to add them here

1. Install features using mvn handler

features:addUrl mvn:org.apache.servicemix.nmr/apache-servicemix-nmr/1.0.0-m2/xml/features
features:install nmr

2. Use file handler to deploy features file

features:addUrl file:base/features/features.xml

Remark : The path is relative to the Apache Karaf installation directory

3. Deploy bundles from file system without using maven

A simple configuration file located in [FELIX:karaf]/etc/org.apache.karaf.features.cfg can be modified to customize the behavior when starting the Kernel for the first time.
This configuration file contains two properties:

• featuresBoot: a comma separated list of features to install at startup
• featuresRepositories: a comma separated list of feature repositories to load at startup

The xml features repositories use the following Relax NG Compact syntax:

element features {
  element repository { text }*
  element feature {
    attribute name { text },
    attribute version { text },
    element feature { 
      attribute version { text },
      text 
    }*,
    element config {
      attribute name { text },
      text
    }*,
    element bundle { text }*
  }*
}

Here is an example of such a repository:

<features>
    <feature name="spring" version="2.5.6.SEC01">
        <bundle>mvn:org.apache.servicemix.bundles/org.apache.servicemix.bundles.aopalliance/1.0_1</bundle>
        <bundle>mvn:org.springframework/spring-core/2.5.6.SEC01</bundle>
        <bundle>mvn:org.springframework/spring-beans/2.5.6.SEC01</bundle>
        <bundle>mvn:org.springframework/spring-aop/2.5.6.SEC01</bundle>        
        <bundle>mvn:org.springframework/spring-context/2.5.6.SEC01</bundle>
        <bundle>mvn:org.springframework/spring-context-support/2.5.6.SEC01</bundle>
    </feature>
</features>

A repository includes a list of feature elements, each one representing an application that can be installed. The feature is identified by its name which must be unique amongst all the repositories used and consists of a set of bundles that need to be installed along with some optional dependencies on other features and some optional configurations for the Configuration Admin OSGi service.

References to features define in other repositories are allow and can be achieved by adding a list of repository.

<features>
  <repository>mvn:org.apache.servicemix.nmr/apache-servicemix-nmr/1.2.0/xml/features</repository>
  <repository>mvn:org.apache.camel.karaf/apache-camel/2.2.0/xml/features</repository>
  <repository>mvn:org.apache.felix.karaf/apache-felix-karaf/1.4.0/xml/features</repository>
  ...

Be carefull when you define them as there is a risk of 'cycling' dependencies.

Remark : By default, all the features defined in a repository are not installed at the launch of Apache Karaf (see section hereafter 'h2. Service configuration' for more info).

The main information provided by a feature is the set of OSGi bundles that defines the application. Such bundles are URLs pointing to the actual bundle jars. For example, one would write the following definition:

<bundle>http://repo1.maven.org/maven2/org/apache/servicemix/nmr/org.apache.servicemix.nmr.api/1.0.0-m2/org.apache.servicemix.nmr.api-1.0.0-m2.jar</bundle>

Doing this will make sure the above bundle is installed while installing the feature.

However, Karaf provides several URL handlers, in addition to the usual ones (file, http, etc...). One of these is the maven URL handler, which allow reusing maven repositories to point to the bundles.

The equivalent of the above bundle would be:

<bundle>mvn:org.apache.servicemix.nmr/org.apache.servicemix.nmr.api/1.0.0-m2</bundle>

In addition to being less verbose, the maven url handlers can also resolve snapshots and can use a local copy of the jar if one is available in your maven local repository.

The org.ops4j.pax.url.mvn bundle resolves mvn URLs. This flexible tool can be configured through the configuration service. For example, to find the current repositories type:

karaf@root:/> config:list
...
----------------------------------------------------------------
Pid:            org.ops4j.pax.url.mvn
BundleLocation: mvn:org.ops4j.pax.url/pax-url-mvn/0.3.3
Properties:
   service.pid = org.ops4j.pax.url.mvn
   org.ops4j.pax.url.mvn.defaultRepositories = file:/opt/development/karaf/assembly/target/apache-felix-karaf-1.2.0-SNAPSHOT/system@snapshots
   org.ops4j.pax.url.mvn.repositories = http://repo1.maven.org/maven2, 
                                         http://people.apache.org/repo/m2-snapshot-repository@snapshots@noreleases, 
                                         http://repository.ops4j.org/maven2, 
                                         http://svn.apache.org/repos/asf/servicemix/m2-repo 
   below = list of repositories and even before the local repository

The repositories checked are controlled by these configuration properties.

Available since Karaf 2.0

By default, the bundles deployed through the feature mechanism will have a start-level equals to the value defined in the configuration file config.properties
with the variable karaf.startlevel.bundle=60. This value can be changed using the xml attribute start-level.

  <feature name='my-project' version='1.0.0'>
    <feature version='2.4.0'>camel-spring</feature>
    <bundle start-level='80'>mvn:com.mycompany.myproject/myproject-dao</bundle>    
    <bundle start-level='85'>mvn:com.mycompany.myproject/myproject-service</bundle>
    <bundle start-level='85'>mvn:com.mycompany.myproject/myproject-camel-routing</bundle>
  </feature> 

The advantage to define the start-level of a bundle is that you can deploy all your bundles including those of the project with the 'infrastructure' bundles required (e.g : camel, activemq)
at the same time and you will have the guaranty when you use Spring Dynamic Module (to register service through OSGI service layer), Blueprint that by example
Spring context will not be created without all the required services installed.

Available since Karaf 2.0

The OSGI specification allows to install a bundle without starting it. To use this functionality, simply add the following attribute in your <bundle> definition

  <feature name='my-project' version='1.0.0'>
    <feature version='2.4.0'>camel-spring</feature>
    <bundle start-level='80' start='false'>mvn:com.mycompany.myproject/myproject-dao</bundle>    
    <bundle start-level='85' start='false'>mvn:com.mycompany.myproject/myproject-service</bundle>
    <bundle start-level='85' start='false'>mvn:com.mycompany.myproject/myproject-camel-routing</bundle>
  </feature> 

Dependent features are useful when a given feature depends on another feature to be installed. Such a dependency can be expressed easily in the feature definition:

<feature name="jbi">
  <feature>nmr</feature>
  ...
</feature>

The effect of such a dependency is to automatically install the required nmr feature when the jbi feature will be installed.

The configuration section allows to deploy configuration for the OSGi Configuration Admin service along a set of bundles.
Here is an example of such a configuration:

<config name="com.foo.bar">
  myProperty = myValue
</config>

The name attribute of the configuration element will be used as the ManagedService PID for the configuration set in the Configuration Admin service. When using a ManagedServiceFactory, the name attribute is servicePid-aliasId, where servicePid is the PID of the ManagedServiceFactory and aliasId is a label used to uniquely identify a particular service (an alias to the factory generated service PID).

Deploying such a configuration has the same effect than dropping a file named com.foo.bar.cfg into the etc folder.

Karaf provides some commands to administer multiple instances. An instance of Karaf is a copy that you can launch separately and deploy applications onto. An instance does not contain a full copy of Karaf, but only a copy of the configuration files and data folder which contains all runtime informations, logs and temporary files.

Those commands are also available from outside the OSGi environment using the admin/admin.bat script in the bin folder.

The files in the etc directory are used to set the startup configuration.

For dynamic configuration, Karaf provides a suite of command to administer the configuration service grouped under config. To learn about all currently supported configuration commands type:

For example to edit configuration foo.bar:

karaf@root:/> config:edit foo.bar

Use:

• config:proplist to list existing properties
• config:propdel to delete existing properties
• config:propset to set a new value for a property

Any number of properties can be modified within a single editing session.

Use

• config:update to commit all changes made in the current session
• config:cancel to roll back any changes made in the current session

TODO

TODO

This chapter will guide you through the steps needed to extend the console and create a new shell. We will leverage Maven, Blueprint and OSGi, so you will need some knowledge of those products.

We first need to create the project using maven. Let's leverage maven archetypes for that.

Using the command line, we can create our project:

mvn archetype:create \
  -DarchetypeArtifactId=maven-archetype-quickstart \
  -DgroupId=org.apache.karaf.shell.samples \
  -DartifactId=shell-sample-commands \
  -Dversion=1.0-SNAPSHOT

This generate the main pom.xml and some additional packages.

You can also use the interactive mode for creating the skeleton project:

mvn archetype:generate

Use the following values when prompted:

Choose a number:  (1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32/33/34/35/36) 15: : 15
Define value for groupId: : org.apache.karaf.shell.samples
Define value for artifactId: : shell-sample-commands
Define value for version:  1.0-SNAPSHOT: : 
Define value for package: : org.apache.karaf.shell.samples

Alternatively, you can simply create the directory shell-sample-commands and create the pom.xml file inside it:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.apache.karaf.shell.samples</groupId>
  <artifactId>shell-sample-commands<artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>shell-sample-commmands</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>

We need to tell maven which libraries our project depends on. In the dependencies section of the pom, add the following one:

  <dependency>
    <groupId>org.apache.karaf.shell</groupId>
    <artifactId>org.apache.karaf.shell.console</artifactId>
    <version>1.0.0</version>
  </dependency>

This dependency is needed to have access to the base classes that are used to define commands.

We are using annotations to define commands, so we need to ensure maven will actually use JDK 1.5 to compile the jar.
Just add the following snippet after the dependencies section.

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <configuration>
        <target>1.5</target>
        <source>1.5</source>
      </configuration>
    </plugin>
  </plugins>
</build>

We can use maven to generate the needed files for your IDE:

Inside the project, run the following command

mvn eclipse:eclipse

or

mvn idea:idea

The project files for your IDE should now be created. Just open the IDE and load the project.

We can now create the command class HelloShellCommand.java

package org.apache.karaf.shell.samples;

import org.apache.felix.gogo.commands.Command;
import org.apache.felix.gogo.commands.Option;
import org.apache.felix.gogo.commands.Argument;
import org.apache.karaf.shell.console.OsgiCommandSupport;

@Command(scope = "test", name = "hello", description="Says hello")
public class HelloShellCommand extends OsgiCommandSupport {

    @Override
    protected Object doExecute() throws Exception {
        System.out.println("Executing Hello command");
        return null;
    }
}

The blueprint configuration file will be used to create the command and register it in the OSGi registry, which is the way to make the command available to Karaf console. This blueprint file must be located in the OSGI-INF/blueprint/ directory inside the bundle.

If you don't have the src/main/resources directory yet, create it.

mkdir src/main/resources

Then, re-generate the IDE project files and reload it so that this folder is now recognized as a source folder.

Inside this directory, create the OSGI-INF/blueprint/ directory and put the following file inside (the name of this file has no impact at all):

<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0">

    <command-bundle xmlns="http://karaf.apache.org/xmlns/shell/v1.0.0">
        <command name="test/hello">
            <action class="org.apache.karaf.shell.samples.HelloShellCommand"/>
        </command>
    </command-bundle>

</blueprint>

Let's try to build the jar. Remove the test classes and sample classes if you used the artifact, then from the command line, run:

mvn install

The end of the maven output should look like:

[SMX4KNL:INFO] ------------------------------------------------------------------------
[SMX4KNL:INFO] BUILD SUCCESSFUL
[SMX4KNL:INFO] ------------------------------------------------------------------------

OSGi bundles are jars but they require some manifest headers to be correctly recognized. We will leverage Felix's maven plugin to easily generate those.

Lets turn it into a bundle: modify the line in the pom.xml to adjust the packaging:

  <packaging>bundle</packaging>

Add the following section at the bottom of the pom.xml, in the existing build/plugins section:

      <plugin>
        <groupId>org.apache.felix</groupId>
        <artifactId>maven-bundle-plugin</artifactId>
        <version>2.1.0</version>
        <extensions>true</extensions>
        <configuration>
            <instructions>
                <Import-Package>org.osgi.service.command,*</Import-Package>
            </instructions>
        </configuration>
      </plugin>

The Import-Package is required to make sure our bundle will import the org.osgi.service.command package so that the service will be correctly seen in Felix.

Let's compiled it again using the mvn install command.

Launch a Karaf instance and run the following command to install the newly created bundle:

karaf@root> osgi:install -s mvn:org.apache.karaf.shell.samples/shell-sample-commands/1.0-SNAPSHOT

Let's try running the command:

karaf@root> test:hello
Executing Hello command

A completer allow you to automatically complete a command argument using <tab>. A completer is simply a bean which is injected to a command.

Of course to be able to complete it, the command should require an argument.

We add an argument to the HelloCommand:

package org.apache.karaf.shell.samples;

import org.apache.felix.gogo.commands.Command;
import org.apache.felix.gogo.commands.Option;
import org.apache.felix.gogo.commands.Argument;
import org.apache.karaf.shell.console.OsgiCommandSupport;

@Command(scope = "test", name = "hello", description="Says hello")
public class HelloShellCommand extends OsgiCommandSupport {

    @Argument(index = 0, name = "arg", description = "The command argument", required = false, multiValued = false)
    String arg = null;

    @Override
    protected Object doExecute() throws Exception {
        System.out.println("Executing Hello command");
        return null;
    }
}

The Blueprint configuration file is the same as previously.

A completer is a bean which implements the Completer interface:

package org.apache.karaf.shell.samples;

import org.apache.karaf.shell.console.completer.StringsCompleter;
import org.apache.karaf.shell.console.Completer;

/**
 * <p>
 * A very simple completer.
 * </p>
 */
public class SimpleCompleter implements Completer {

 /**
  * @param buffer it's the beginning string typed by the user
  * @param cursor it's the position of the cursor
  * @param candidates the list of completions proposed to the user
  */
 public int complete(String buffer, int cursor, List candidates) {
  StringsCompleter delegate = new StringsCompleter();
  delegate.getStrings().add("one");
  delegate.getStrings().add("two");
  delegate.getStrings().add("three");
  return delegate.complete(buffer, cursor, candidates);
 }

}

Using Blueprint, you can "inject" the completer linked to your command. The same completer could be used for several commands and a command can have several completers:

<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0">

    <command-bundle xmlns="http://karaf.apache.org/xmlns/shell/v1.0.0">
        <command name="test/hello">
            <action class="org.apache.karaf.shell.samples.HelloShellCommand"/>
        </command>
        <completers>
          <ref component-id="simpleCompleter"/>
          <null/>
        </completers>
    </command-bundle>

    <bean id="simpleCompleter" class="org.apache.karaf.shell.samples.SimpleCompleter"/>

</blueprint>

Launch a Karaf instance and run the following command to install the newly created bundle:

karaf@root> osgi:install -s mvn:org.apache.karaf.shell.samples/shell-sample-commands/1.0-SNAPSHOT

Let's try running the command:

karaf@root> test:hello <tab>
 one    two    three

A connection to Karaf console can also be done programmatically.
The following code is a simplified version of the code from the client library.

import org.apache.sshd.ClientChannel;
import org.apache.sshd.ClientSession;
import org.apache.sshd.SshClient;
import org.apache.sshd.client.future.ConnectFuture;

public class Main {

    public static void main(String[] args) throws Exception {
        String host = "localhost";
        int port = 8101;
        String user = "karaf";
        String password = "karaf";

        SshClient client = null;
        try {
            client = SshClient.setUpDefaultClient();
            client.start();
            ConnectFuture future = client.connect(host, port);
            future.await();
            ClientSession session = future.getSession();
            session.authPassword(user, password);
            ClientChannel channel = session.createChannel("shell");
            channel.setIn(System.in);
            channel.setOut(System.out);
            channel.setErr(System.err);
            channel.open();
            channel.waitFor(ClientChannel.CLOSED, 0);
        } catch (Throwable t) {
            t.printStackTrace();
            System.exit(1);
        } finally {
            try {
                client.stop();
            } catch (Throwable t) { }
        }
        System.exit(0);
    }

}

TODO: an example of embedding Karaf inside a web application is provided in the distribution

This chapter will demonstrate how to add additional features from a remote maven repository to a default installation of Karaf.

Last updated September 3, 2010 using Karaf 2.0.0

The following steps will add in the missing OPS4J and Apache Snapshot maven repositories. Note - this has been fixed in the 1.1.0 of ServiceMix Kernel release and can be skipped.

1. Edit the following file -

   etc/org.ops4j.pax.url.mvn.cfg
   

2. Update org.ops4j.pax.url.mvn.repositories to include the OPS4J and Apache Snapshot repos -

   org.ops4j.pax.url.mvn.repositories=file:${user.home}/.m2/repository@snapshots,http://repo1.maven.org/maven2,http://repository.ops4j.org/maven2,http://people.apache.org/repo/m2-snapshot-repository@snapshots@noreleases
   

The following steps will add in the URLs for the Camel & ActiveMQ and Features locations.

1. Start Karaf

   cd bin
   ./karaf or karaf.bat
   

2. Add the following feature install locations

   karaf@root> features:addUrl mvn:org.apache.activemq/activemq-karaf/5.4.0/xml/features
   karaf@root> features:addUrl mvn:org.apache.camel.karaf/features/2.0.0/xml/features
   
   

3. Verify the feature URLs were added -

   karaf@root> features:listUrl
   mvn:org.apache.camel.karaf/features/2.0.0/xml/features    valid
   mvn:org.apache.activemq/activemq-karaf/5.4.0/xml/features    valid
   mvn:org.apache.karaf/apache-karaf/2.0.1-SNAPSHOT/xml/features    valid
   

The following steps will install the "war" feature (support for deploying WAR files with Servlet and JSPs into a Jetty server) into your Karaf instance.

The following steps will describe how to install a simple WAR file (with JSPs or Servlets) to the just installed web feature.

This chapter will demonstrate how to configure failover deployments.

The simple lock file mechanism is intended for failover configurations where instances reside on the same host machine.

To use this feature, edit the $KARAF_HOME/etc/system.properties file as follows on each system in the master/slave setup:

karaf.lock=true
karaf.lock.class=org.apache.felix.karaf.main.SimpleFileLock
karaf.lock.dir=<PathToLockFileDirectory>
karaf.lock.delay=10

Note: Ensure that the karaf.lock.dir property points to the same directory for both the master and slave instance, so that the slave can only acquire the lock when the master releases it.

The JDBC locking mechanism is intended for failover configurations where instances exist on separate machines. In this deployment, the master instance holds a lock on a Karaf locking table hosted on a database. If the master loses the lock, a waiting slave process gains access to the locking table and fully starts its container.

To use this feature, do the following on each system in the master/slave setup:

• Update the classpath to include the JDBC driver
• Update the $KARAF_HOME/bin/karaf script to have unique JMX remote port set if instances reside on the same host
• Update the $KARAF_HOME/etc/system.properties file as follows:

karaf.lock=true
karaf.lock.class=org.apache.felix.karaf.main.DefaultJDBCLock
karaf.lock.level=50
karaf.lock.delay=10
karaf.lock.jdbc.url=jdbc:derby://dbserver:1527/sample
karaf.lock.jdbc.driver=org.apache.derby.jdbc.ClientDriver
karaf.lock.jdbc.user=user
karaf.lock.jdbc.password=password
karaf.lock.jdbc.table=KARAF_LOCK
karaf.lock.jdbc.clustername=karaf
karaf.lock.jdbc.timeout=30

Note:

• Will fail if JDBC driver is not on classpath.
• The database name "sample" will be created if it does not exist on the database.
• The first Karaf instance to acquire the locking table is the master instance.
• If the connection to the database is lost, the master instance tries to gracefully shutdown, allowing a slave instance to become master when the database service is restored. The former master will require manual restart.

If you are using Oracle as your database in a JDBC locking scenario, the karaf.lock.class property in the $KARAF_HOME/etc/system.properties file must point to org.apache.felix.karaf.main.OracleJDBCLock.

Otherwise, configure the system.properties file as normal for your setup, for example:

karaf.lock=true
karaf.lock.class=org.apache.felix.karaf.main.OracleJDBCLock
karaf.lock.jdbc.url=jdbc:oracle:thin:@hostname:1521:XE
karaf.lock.jdbc.driver=oracle.jdbc.OracleDriver
karaf.lock.jdbc.user=user
karaf.lock.jdbc.password=password
karaf.lock.jdbc.table=KARAF_LOCK
karaf.lock.jdbc.clustername=karaf
karaf.lock.jdbc.timeout=30

As with the default JDBC locking setup, the Oracle JDBC driver JAR file must be in your classpath. You can ensure this by copying the ojdbc14.jar into Karaf's lib folder before starting Karaf.

Note: The karaf.lock.jdbc.url requires an active SID, which means you must manually create a database instance before using this particular lock.

Container-level locking allows bundles to be preloaded into the slave kernel instance in order to provide faster failover performance. Container-level locking is supported in both the simple file and JDBC locking mechanisms.

To implement container-level locking, add the following to the $KARAF_HOME/etc/system.properties file on each system in the master/slave setup:

karaf.lock=true
karaf.lock.level=50
karaf.lock.delay=10

The karaf.log.level property tells the Karaf instance how far up the boot process to bring the OSGi container. Bundles assigned the same start level or lower will then also be started in that Karaf instance.

Bundle start levels are specified in $KARAF_HOME/etc/startup.properties, in the format jar.name=level. The core system bundles have levels below 50, where as user bundles have levels greater than 50.

Note: When using a 'hot' spare on the same host you need to set the JMX remote port to a unique value to avoid bind conflicts. You can edit the Karaf start script to include the following:

DEFAULT_JAVA_OPTS="-server $DEFAULT_JAVA_OPTS -Dcom.sun.management.jmxremote.port=1100 -Dcom.sun.management.jmxremote.authenticate=false"