# Shadowing

## Introduction

Shadowing is a feature that lets a user connect to, view, and interact with ThinLinc sessions of other users. This can be useful in remote assistance and support scenarios, where trusted support personnel can connect to a user session and aid with for example application problems.

Because shadowing gives the shadowing user full control over the shadowed session, this feature should be used with caution.

The shadowing feature is enabled by default and is configured to ask the user to accept or reject a shadowing request.

## Disable shadowing feature

The shadowing feature is enabled by default when installing ThinLinc. You can disable this feature, if required, using the following command:

    $ sudo tl-config /shadowing/shadowing_mode=reject

When the shadowing feature is disabled, all requests to shadow a user session are actively rejected. Details about the `/shadowing/shadowing_mode` configuration parameter is described in Parameters in /shadowing/.

Note

The above command should be run on all of the ThinLinc servers in your cluster.

## Granting shadowing access to users

Because of the security implications of this feature, the system administrator needs to grant this permission to named users and/or groups before it can be used.

The vsmserver service controls whether a user requesting to shadow another user is authorized to do so. The configuration parameter `/shadowing/allowed_shadowers` from the `/opt/thinlinc/etc/conf.d/shadowing.hconf` file is read by the vsmserver service on startup. This parameter is described in detail in Parameters in /shadowing/.

Note

After the configuration variable has been set, the `vsmserver` service needs to be restarted before the change is made active.

## Shadowing notification

Notification behavior of the shadowing feature is configured by the system administrator. The notification mechanism can be configured in four different modes as described here.

- Shadow requests are silently rejected

- Shadow requests are silently accepted

- Shadow requests are accepted and the user is notified

- Shadow requests are interactively accepted or rejected by the user

To configure the shadowing mode, use the following command and select a value of `reject`, `silent`, `notify`, or `ask`. Details about the `/shadowing/shadowing_mode` configuration parameter are described in Parameters in /shadowing/.

    $ sudo tl-config /shadowing/shadowing_mode=ask

Note

The above command should be run on all ThinLinc servers in your cluster.

Note

Only newly started session are affected by the above change.

## Shadowing a user session

The ThinLinc client must be configured for shadowing. See Advanced tab for more information.

Once the client has been configured for shadowing, enter the username of the user you wish to shadow in the User to shadow field and connect.