MettleCI and its associated systems make use of SSH (a form of public key cryptography) to provide secure communications channels between software components running on different hosts. This page provides an outline of the MettleCI-related components which use SSH, and a high-level view of how those components should be configured.

Files relevant to MettleCI

The misconfiguration of SSH-related files on the DataStage Engine on which you have MettleCI Workbench installed can give rise to various symptoms, most of which are characterised by the failure of one system to form a trusted connection with another. This page describes the SSH components relevant to MettleCI, and how those components should be configured for successful operation.This page assumes you are running MettleCI Workbench on a Unix-based host under a user called mciworkb (link).

MettleCI CLI

MettleCI CLI commands most commonly execute on the MettleCI Agent Host (described here) and communicate with the DataStage Engine to perform build and deployment tasks. Those commands which communicate over SSH (most notably those from the Remote Namespace with the privateKey option) are dependent upon correct configuration of the SSH between these two hosts.

In the diagram above the MettleCI Agent Host (described here) stores a private key file (named client.key in the diagram above) for which the public key equivalent (e.g. client.key.pub) is stored inside the ~/.ssh/authorized_keys file of the user account you are using to execute the MettleCI Workbench - typically mciworkb. This permits SSH connection between the MettleCI Agent Host and your DataStage Engine upon which the MettleCI Workbench is running. This connection is, most notably, required when using MettleCI commands from the Remote Namespace with the privateKey option.

Similarly, your DataStage Engine will store a private key file (an example of which is created during MettleCI installation - workbench.key) in the MettleCI installation directory - typically /opt/dm/mci. The the public key equivalent (e.g. workbench.key.pub) is shared with third party systems with which your DataStage engine needs to communicate - most commonly your Git and Work Item Management platforms.

MettleCI CLI

Some MettleCI CLI commands which communicate with the DataStage Engine tier are dependent upon the correct configuration of the mciworkb user's .ssh folder and its contents.

Directory /mciworkb/.ssh

The directory /home/mciworkb/.sshshould have the following properties:

...

$> ls -ld /home/mciworkb/.ssh
drwx------ 2 rootmciworkb rootdstage 144 Feb 16 14:3126 .ssh

These properties can be established with the following commands:

...

$> ls -ld /home/mciworkb/.ssh/authorized_keys
-rw------- 1 mciworkb dstage 1167 Feb 16 14:2631 .ssh/authorized_keys

Third Party Systems

SSH may also be involved in MettleCI Workbench’s communication with Work Item Management and Git platforms. In these cases you will use a SSH key pair crated created hosted on the DataStage Engine to form this connection. Your DataStage Engine will store a private key file, an example of which (workbench.key) is created in the MettleCI directory (typically /opt/dm/mci) during MettleCI installation. The the public key will be equivalent (e.g. workbench.key.pub) is supplied to the third party system which will use this when communicating with your DataStage Engine tiersystems with which your DataStage engine needs to communicate - most commonly your Git and Work Item Management platforms. You can either use the key pair created for you by the MettleCI installation process (workbench.key / workbench.key.pub, which is a 521-bit ECDSA key) or create your own if your organisation or third party system have specified SSH key requirements. The process varies from tool to tool, so please see the relevant MettleCI documentation for tools relevant to you.

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