Remote

Apache Karaf supports a complete remote mechanism allowing you to remotely connect to a running Apache Karaf instance. More over, you can also browse, download, and upload files remotely to a running Apache Karaf instance.

Apache Karaf embeds a complete SSHd server.

SSHd server

When you start Apache Karaf, it enables a remote console that can be accessed over SSH.

This remote console provides all the features of the "local" console, and gives a remote user complete control over the container and services running inside of it. As the "local" console, the remote console is secured by a RBAC mechanism (see the Security section of the user guide for details).

In addition to the remote console, Apache Karaf also provides a remote filesystem. This remote filesystem can be accessed using a SCP/SFTP client.

Configuration

The configuration of the SSHd server is stored in the etc/org.apache.karaf.shell.cfg file:

################################################################################
#
#    Licensed to the Apache Software Foundation (ASF) under one or more
#    contributor license agreements.  See the NOTICE file distributed with
#    this work for additional information regarding copyright ownership.
#    The ASF licenses this file to You under the Apache License, Version 2.0
#    (the "License"); you may not use this file except in compliance with
#    the License.  You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS,
#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#    See the License for the specific language governing permissions and
#    limitations under the License.
#
################################################################################

#
# These properties are used to configure Karaf's ssh shell.
#

#
# Via sshPort and sshHost you define the address you can login into Karaf.
#
sshPort = 8101
sshHost = 0.0.0.0

#
# The sshIdleTimeout defines the inactivity timeout to logout the SSH session.
# The sshIdleTimeout is in milliseconds, and the default is set to 30 minutes.
#
sshIdleTimeout = 1800000

#
# sshRealm defines which JAAS domain to use for password authentication.
#
sshRealm = karaf

#
# The location of the hostKey file defines where the private key of the server
# is located. If no file is at the defined location it will be ignored.
#
hostKey = ${karaf.etc}/host.key

#
# The location of the hostKeyPub file defines where the public key of the server
# is located. If no file is at the defined location it will be ignored.
#
#hostKeyPub = ${karaf.etc}/host.key.pub

#
# sshRole defines the role required to access the console through ssh
#
# sshRole = ssh

#
# Defines if the SFTP system is enabled or not in the SSH server
#
sftpEnabled=true

#
# Self defined key size in 1024, 2048, 3072, or 4096
# If not set, this defaults to 2048.
#
# keySize = 2048

#
# Specify host key algorithm, defaults to RSA
#
# algorithm = RSA

#
# Defines the completion mode on the Karaf shell console. The possible values are:
# - GLOBAL: it's the same behavior as in previous Karaf releases. The completion displays all commands and all aliases
#           ignoring if you are in a subshell or not.
# - FIRST: the completion displays all commands and all aliases only when you are not in a subshell. When you are
#          in a subshell, the completion displays only the commands local to the subshell.
# - SUBSHELL: the completion displays only the subshells on the root level. When you are in a subshell, the completion
#             displays only the commands local to the subshell.
# This property define the default value when you use the Karaf shell console.
# You can change the completion mode directly in the shell console, using shell:completion command.
#
completionMode = GLOBAL

The etc/org.apache.karaf.shell.cfg configuration file contains different properties to configure the SSHd server:

  • sshPort is the port number where the SSHd server is bound (by default, it’s 8101).

  • sshHost is the address of the network interface where the SSHd server is bound. The default value is 0.0.0.0, meaning that the SSHd server is bound on all network interfaces. You can bind on a target interface by providing the IP address of the network interface.

  • hostKey is the location of the host.key file. By defaut, it uses etc/host.key. This file stores the private key of the SSHd server.

  • sshRole is the default role used for SSH access. See the [Security section|security] of this user guide for details.

  • sftpEnabled controls if the SSH server starts the SFTP system or not. When enabled, Karaf SSHd supports SFTP, meaning that you can remotely access the Karaf filesystem with any sftp client.

  • keySize is the key size used by the SSHd server. The possible values are 1024, 2048, 3072, or 4096. The default value is 2048.

  • algorithm is the host key algorithm used by the SSHd server. The possible values are DSA, EC or RSA. The default value is RSA.

The SSHd server configuration can be changed at runtime:

  • by editing the etc/org.apache.karaf.shell.cfg configuration file

  • by using the config:* commands

At runtime, when you change the SSHd server configuration, you have to restart the SSHd server to load the changes. You can do it with:

karaf@root()> bundle:restart -f org.apache.karaf.shell.ssh

The Apache Karaf SSHd server supports key/agent authentication and password authentication.

Console clients
System native clients

The Apache Karaf SSHd server is a pure SSHd server, similar to a OpenSSH daemon.

It means that you can directly use a SSH client from your system.

For instance, on Unix, you can directly use OpenSSH:

~$ ssh -p 8101 karaf@localhost
Authenticated with partial success.
Authenticated with partial success.
Authenticated with partial success.
Password authentication
Password:
        __ __                  ____
       / //_/____ __________ _/ __/
      / ,<  / __ `/ ___/ __ `/ /_
     / /| |/ /_/ / /  / /_/ / __/
    /_/ |_|\__,_/_/   \__,_/_/

  Apache Karaf (4.0.0)

Hit '<tab>' for a list of available commands
and '[cmd] --help' for help on a specific command.
Hit 'system:shutdown' to shutdown Karaf.
Hit '<ctrl-d>' or type 'logout' to disconnect shell from current session.

karaf@root()>

On Windows, you can use Putty, Kitty, etc.

If you don’t have a SSH client installed on your machine, you can use the Apache Karaf client.

ssh:ssh command

Apache Karaf itself provides a SSH client. When you are on the Apache Karaf console, you have the ssh:ssh command:

karaf@root()> ssh:ssh --help
DESCRIPTION
        ssh:ssh

        Connects to a remote SSH server

SYNTAX
        ssh:ssh [options] hostname [command]

ARGUMENTS
        hostname
                The host name to connect to via SSH
        command
                Optional command to execute

OPTIONS
        --help
                Display this help message
        -p, --port
                The port to use for SSH connection
                (defaults to 22)
        -P, --password
                The password for remote login
        -q
                Quiet Mode. Do not ask for confirmations
        -l, --username
                The user name for remote login

Thanks to the ssh:ssh command, you can connect to another running Apache Karaf instance:

karaf@root()> ssh:ssh -p 8101 karaf@192.168.134.2
Connecting to host 192.168.134.2 on port 8101
Connecting to unknown server. Add this server to known hosts ? (y/n)
Storing the server key in known_hosts.
Connected
        __ __                  ____
       / //_/____ __________ _/ __/
      / ,<  / __ `/ ___/ __ `/ /_
     / /| |/ /_/ / /  / /_/ / __/
    /_/ |_|\__,_/_/   \__,_/_/

  Apache Karaf (4.0.0)

Hit '<tab>' for a list of available commands
and '[cmd] --help' for help on a specific command.
Hit 'system:shutdown' to shutdown Karaf.
Hit '<ctrl-d>' or type 'logout' to disconnect shell from current session.

karaf@root()>

When you don’t provide the command argument to the ssh:ssh command, you are in the interactive mode: you have a complete remote console available, where you can type commands, etc.

You can also provide directly a command to execute using the command argument. For instance, to remotely shutdown a Apache Karaf instance:

karaf@root()> ssh:ssh -p 8101 karaf@localhost system:shutdown -f
Connecting to host localhost on port 8101
Connected

As the ssh:ssh command is a pure SSH client, it means that you can connect to a Unix OpenSSH daemon:

karaf@root()> ssh:ssh user@localhost
Connecting to host localhost on port 22
Connecting to unknown server. Add this server to known hosts ? (y/n)
Storing the server key in known_hosts.
Agent authentication failed, falling back to password authentication.
Password: Connected
Last login: Sun Sep  8 19:21:12 2013
user@server:~$
Apache Karaf client

The ssh:ssh command can only be run in a running Apache Karaf console.

For convenience, the ssh:ssh command is "wrapped" as a standalone client: the bin/client Unix script (bin\client.bat on Windows).

bin/client --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
  --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)
  -b            batch mode, specify multiple commands via standard input
  -f [file]     read commands from the specified file
  [commands]    commands to run
If no commands are specified, the client will be put in an interactive mode

For instance, to connect to a local Apache Karaf instance (on the default SSHd server 8101 port), you can directly use bin/client Unix script (bin\client.bat on Windows) without any argument or option:

bin/client
Logging in as karaf
343 [pool-2-thread-4] WARN org.apache.sshd.client.keyverifier.AcceptAllServerKeyVerifier - Server at /0.0.0.0:8101 presented unverified key:
        __ __                  ____
       / //_/____ __________ _/ __/
      / ,<  / __ `/ ___/ __ `/ /_
     / /| |/ /_/ / /  / /_/ / __/
    /_/ |_|\__,_/_/   \__,_/_/

  Apache Karaf (4.0.0)

Hit '<tab>' for a list of available commands
and '[cmd] --help' for help on a specific command.
Hit 'system:shutdown' to shutdown Karaf.
Hit '<ctrl-d>' or type 'logout' to disconnect shell from current session.

karaf@root()>

When you don’t provide the command argument to the bin/client Unix script (bin\client.bat on Windows), you are in the interactive mode: you have a complete remote console available, where you can type commands, etc.

You can also provide directly a command to execute using the command argument. For instance, to remotely shutdown a Apache Karaf instance:

bin/client "system:shutdown -f"
Logging in as karaf
330 [pool-2-thread-3] WARN org.apache.sshd.client.keyverifier.AcceptAllServerKeyVerifier - Server at /0.0.0.0:8101 presented unverified key:

As the Apache Karaf client is a pure SSH client, you can use to connect to any SSHd daemon (like Unix OpenSSH daemon):

bin/client -a 22 -h localhost -u user
Logging in as user
353 [pool-2-thread-2] WARN org.apache.sshd.client.keyverifier.AcceptAllServerKeyVerifier - Server at localhost/127.0.0.1:22 presented unverified key:
Password:
Welcome to Ubuntu 13.10 (GNU/Linux 3.11.0-13-generic x86_64)

 * Documentation:  https://help.ubuntu.com/

Last login: Tue Dec  3 18:18:31 2013 from localhost
Logout

When you are connected to a remote Apache Karaf console, you can logout using:

  • using CTRL-D key binding. Note that CTRL-D just logs out from the remote console in this case, it doesn’t shutdown the Apache Karaf instance (as CTRL-D does when used on a local console).

  • using shell:logout command (or simply logout)

Filesystem clients

Apache Karaf SSHd server also provides complete fileystem access via SSH. For security reasons, the available filesystem is limited to KARAF_BASE directory.

You can use this remote filesystem with any SCP/SFTP compliant clients.

Native SCP/SFTP clients

On Unix, you can directly use scp command to download/upload files to the Apache Karaf filesystem. For instance, to retrieve the karaf.log file remotely:

~$ scp -P 8101 karaf@localhost:/data/log/karaf.log .
Authenticated with partial success.
Authenticated with partial success.
Authenticated with partial success.
Password authentication
Password:
karaf.log

As you have access to the complete KARAF_BASE directory, you can remotely change the configuration file in the etc folder, retrieve log files, populate the system folder.

On Windows, you can use WinSCP to access the Apache Karaf filesystem.

It’s probably easier to use a SFTP complient client.

For instance, on a Unix system, you can use lftp or ncftp:

$ lftp
lftp :~> open -u karaf sftp://localhost:8101
Password:
lftp karaf@localhost:~> ls
-rw-r--r--   1 jbonofre jbonofre    27754 Oct 26 10:50 LICENSE
-rw-r--r--   1 jbonofre jbonofre     1919 Dec  3 05:34 NOTICE
-rw-r--r--   1 jbonofre jbonofre     3933 Aug 18  2012 README.md
-rw-r--r--   1 jbonofre jbonofre   101041 Dec  3 05:34 RELEASE-NOTES.md
drwxr-xr-x   1 jbonofre jbonofre     4096 Dec  3 12:51 bin
drwxr-xr-x   1 jbonofre jbonofre     4096 Dec  3 18:57 data
drwxr-xr-x   1 jbonofre jbonofre     4096 Dec  3 12:51 examples
drwxr-xr-x   1 jbonofre jbonofre     4096 Dec  3 13:02 deploy
drwxr-xr-x   1 jbonofre jbonofre     4096 Dec  3 17:59 etc
drwxr-xr-x   1 jbonofre jbonofre     4096 Dec  3 13:02 instances
drwxr-xr-x   1 jbonofre jbonofre     4096 Dec  3 13:02 lib
-rw-r--r--   1 jbonofre jbonofre        0 Dec  3 13:02 lock
drwxr-xr-x   1 jbonofre jbonofre     4096 Dec  3 12:51 system
lftp karaf@localhost:/>

You can also use a graphic client like filezilla, gftp, nautilus, etc.

On Windows, you can use filezilla, WinSCP, etc.

Apache Maven

The Apache Karaf system folder is the Karaf repository, that uses a Maven directory structure. It’s where Apache Karaf looks for the artifacts (bundles, features, kars, etc).

Using Apache Maven, you can populate the system folder using the deploy:deploy-file goal.

For instance, you want to add the Apache ServiceMix facebook4j OSGi bundle, you can do:

mvn deploy:deploy-file -Dfile=org.apache.servicemix.bundles.facebook4j-2.0.2_1.jar -DgroupId=org.apache.servicemix.bundles -DartifactId=org.apache.servicemix.bundles.facebook4j -Dversion=2.0.2_1 -Dpackaging=jar -Durl=scp://localhost:8101/system
Note

If you want to turn Apache Karaf as a simple Maven repository, you can use Apache Karaf Cave.

JMX MBeanServer

Apache Karaf provides a JMX MBeanServer.

This MBeanServer is available remotely, using any JMX client like jconsole.

You can find details on the [Monitoring section|monitoring] of the user guide.