ARTICLES

Connecting to the Karaf Shell

OpenNMS uses Apache Karaf under the hood and in some cases (especially during development) it is required to connect to the OpenNMS Karaf Shell.

First of all OpenNMS must be started to connect to the Karaf Shell. I usually start OpenNMS with the -v (verbose) and -t (debug) options:

$OPENNMS_HOME/bin/opennms -vt start

Afterwards I check with

$OPENNMS_HOME/bin/opennms -v status

until the Jetty Webserver is STARTED, as the Karaf Container is started by the Webapp itself.

Usually you would connect to the shell via

ssh admin@localhost -p 8101 (the password is `admin` as well)

However you most like will get the following error message or something similar

Unable to negotiate with ::1: no matching host key type found. Their offer: ssh-dss

To work around this issue you can connect like this: ssh admin@localhost -p 8101 -oHostKeyAlgorithms=+ssh-dss.

If you got around this, in most cases you will get asked if you want to connect to the unknown host. However, if you hit yes, the next time you connect to the shell, but have rebuilt OpenNMS connection is refused (due to changed host key). So you manually have to remove the entry from ~/.ssh/known_hosts.

Both adding the host key algorithm and deleting the entry from known_hosts is tidious. Therfore my ~/.ssh/config contains the following entry:

Host localhost
     HostKeyAlgorithms +ssh-dss
     StrictHostKeyChecking no
     UserKnownHostsFile=/dev/null