Chapter 3. Installing Guacamole with Docker

Chapter 3. Installing Guacamole with Docker
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Chapter 3. Installing Guacamole with Docker

Table of Contents

Running the guacd Docker image

Running guacd for use by the Guacamole Docker image
Running guacd for use by services outside Docker

The Guacamole Docker image

Configuring Guacamole when using Docker
Connecting Guacamole to guacd
MySQL authentication
PostgreSQL authentication
LDAP authentication
Custom extensions and GUACAMOLE_HOME
Verifying the Guacamole install

Guacamole can be deployed using Docker, removing the need to build guacamole-server from source or configure the web application manually. The Guacamole project provides officially-supported Docker images for both Guacamole and guacd which are kept up-to-date with each release.

A typical Docker deployment of Guacamole will involve three separate containers, linked together at creation time:

guacamole/guacd: Provides the guacd daemon, built from the released guacamole-server source with support for VNC, RDP, SSH, and telnet.
guacamole/guacamole: Provides the Guacamole web application running within Tomcat 8 with support for WebSocket. The configuration necessary to connect to guacd, MySQL, PostgreSQL, LDAP, etc. will be generated automatically when the image starts based on Docker links or environment variables.

mysql or postgresql: Provides the database that Guacamole will use for authentication and storage of connection configuration data.

This separation is important, as it facilitates upgrades and maintains proper separation of concerns. With the database separate from Guacamole and guacd, those containers can be freely destroyed and recreated at will. The only container which must persist data through upgrades is the database.

Running the guacd Docker image

The guacd Docker image is built from the released guacamole-server source with support for VNC, RDP, SSH, and telnet. Common pitfalls like installing the required dependencies, installing fonts for SSH or telnet, and ensuring the FreeRDP plugins are installed to the correct location are all taken care of. It will simply just work.

Running guacd for use by the Guacamole Docker image

When running the guacd image with the intent of linking to a Guacamole container, no ports need be exposed on the network. Access to these ports will be handled automatically by Docker during linking, and the Guacamole image will properly detect and configure the connection to guacd.

$ docker run --name some-guacd -d guacamole/guacd

When run in this manner, guacd will be listening on its default port 4822, but this port will only be available to Docker containers that have been explicitly linked to some-guacd.

The log level of guacd can be controlled with the GUACD_LOG_LEVEL environment variable. The default value is info, and can be set to any of the valid settings for the guacd log flag (-L).

$ docker run -e GUACD_LOG_LEVEL=debug -d guacamole/guacd

Running guacd for use by services outside Docker

If you are not going to use the Guacamole image, you can still leverage the guacd image for ease of installation and maintenance. By exposing the guacd port, 4822, services external to Docker will be able to access guacd.

Important

Take great care when doing this - guacd is a passive proxy and does not perform any kind of authentication.

If you do not properly isolate guacd from untrusted parts of your network, malicious users may be able to use guacd as a jumping point to other systems.

$ docker run --name some-guacd -d -p 4822:4822 guacamole/guacd

guacd will now be listening on port 4822, and Docker will expose this port on the same server hosting Docker. Other services, such as an instance of Tomcat running outside of Docker, will be able to connect to guacd directly.

The Guacamole Docker image

The Guacamole Docker image is built on top of a standard Tomcat 8 image and takes care of all configuration automatically. The configuration information required for guacd and the various authentication mechanisms are specified with environment variables or Docker links given when the container is created.

Important

If using PostgreSQL or MySQL for authentication, you will need to initialize the database manually. Guacamole will not automatically create its own tables, but SQL scripts are provided to do this.

Once the Guacamole image is running, Guacamole will be accessible at http://HOSTNAME:8080/guacamole/, where HOSTNAME is the hostname or address of the machine hosting Docker.

Configuring Guacamole when using Docker

When running Guacamole using Docker, the traditional approach to configuring Guacamole by editing guacamole.properties is less convenient. When using Docker, you may wish to make use of the enable-environment-properties configuration property, which allows you to specify values for arbitrary Guacamole configuration properties using environment variables. This is covered in Chapter 5, Configuring Guacamole.

Connecting Guacamole to guacd

The Guacamole Docker image needs to be able to connect to guacd to establish remote desktop connections, just like any other Guacamole deployment. The connection information needed by Guacamole will be provided either via a Docker link or through environment variables.

If you will be using Docker to provide guacd, and you wish to use a Docker link to connect the Guacamole image to guacd, the connection details are implied by the Docker link:

$ docker run --name some-guacamole \
    --link some-guacd:guacd        \
    ...
    -d -p 8080:8080 guacamole/guacamole

If you are not using Docker to provide guacd, you will need to provide the network connection information yourself using additional environment variables:

Variable	Description
`GUACD_HOSTNAME`	The hostname of the guacd instance to use to establish remote desktop connections. This is required if you are not using Docker to provide guacd.
`GUACD_PORT`	The port that Guacamole should use when connecting to guacd. This environment variable is optional. If not provided, the standard guacd port of 4822 will be used.

The GUACD_HOSTNAME and, if necessary, GUACD_PORT environment variables can thus be used in place of a Docker link if using a Docker link is impossible or undesirable:

$ docker run --name some-guacamole \
    -e GUACD_HOSTNAME=172.17.42.1  \
    -e GUACD_PORT=4822             \
    ...
    -d -p 8080:8080 guacamole/guacamole

A connection to guacd is not the only thing required for Guacamole to work; some authentication mechanism needs to be configured, as well. MySQL, PostgreSQL, and LDAP are supported for this, and are described in more detail in the sections below. If the required configuration options for at least one authentication mechanism are not provided, the Guacamole image will not be able to start up, and you will see an error.

MySQL authentication

To use Guacamole with the MySQL authentication backend, you will need either a Docker container running the mysql image, or network access to a working installation of MySQL. The connection to MySQL can be specified using either environment variables or a Docker link.

Initializing the MySQL database

If your database is not already initialized with the Guacamole schema, you will need to do so prior to using Guacamole. A convenience script for generating the necessary SQL to do this is included in the Guacamole image.

To generate a SQL script which can be used to initialize a fresh MySQL database as documented in Chapter 6, Database authentication:

$ docker run --rm guacamole/guacamole /opt/guacamole/bin/initdb.sh --mysql > initdb.sql

Alternatively, you can use the SQL scripts included with the database authentication.

Once this script is generated, you must:

Create a database for Guacamole within MySQL, such as guacamole_db.
Create a user for Guacamole within MySQL with access to this database, such as guacamole_user.
Run the script on the newly-created database.

The process for doing this via the mysql utility included with MySQL is documented in Chapter 6, Database authentication.

Connecting Guacamole to MySQL

If your MySQL database is provided by another Docker container, and you wish to use a Docker link to connect the Guacamole image to your database, the connection details are implied by the Docker link itself:

$ docker run --name some-guacamole \
    --link some-guacd:guacd         \
    --link some-mysql:mysql        \
    ...
    -d -p 8080:8080 guacamole/guacamole

If you are not using Docker to provide your MySQL database, you will need to provide the network connection information yourself using additional environment variables:

Variable	Description
`MYSQL_HOSTNAME`	The hostname of the database to use for Guacamole authentication. This is required if you are not using Docker to provide your MySQL database.
`MYSQL_PORT`	The port that Guacamole should use when connecting to MySQL. This environment variable is optional. If not provided, the standard MySQL port of 3306 will be used.

The MYSQL_HOSTNAME and, if necessary, MYSQL_PORT environment variables can thus be used in place of a Docker link if using a Docker link is impossible or undesirable:

$ docker run --name some-guacamole \
    --link some-guacd:guacd         \
    -e MYSQL_HOSTNAME=172.17.42.1  \
    ...
    -d -p 8080:8080 guacamole/guacamole

Note that a Docker link to guacd (the --link some-guacd:guacd option above) is not required any more than a Docker link is required for MySQL. The connection information for guacd can be specified using environment variables, as described in the section called “Connecting Guacamole to guacd”.

Required environment variables

Using MySQL for authentication requires additional configuration parameters specified via environment variables. These variables collectively describe how Guacamole will connect to MySQL:

Variable	Description
`MYSQL_DATABASE`	The name of the database to use for Guacamole authentication.
`MYSQL_USER`	The user that Guacamole will use to connect to MySQL.
`MYSQL_PASSWORD`	The password that Guacamole will provide when connecting to MySQL as `MYSQL_USER`.

If any required environment variables are omitted, you will receive an error message in the logs, and the image will stop. You will then need to recreate the container with the proper variables specified.

Optional environment variables

Additional optional environment variables may be used to override Guacamole's default behavior with respect to concurrent connection use by one or more users. Concurrent use of connections and connection groups can be limited to an overall maximum and/or a per-user maximum:

Variable	Description
`MYSQL_ABSOLUTE_MAX_CONNECTIONS`	The absolute maximum number of concurrent connections to allow at any time, regardless of the Guacamole connection or user involved. If set to "0", this will be unlimited. Because this limit applies across all Guacamole connections, it cannot be overridden if set. By default, the absolute total number of concurrent connections is unlimited ("0").
`MYSQL_DEFAULT_MAX_CONNECTIONS`	The maximum number of concurrent connections to allow to any one Guacamole connection. If set to "0", this will be unlimited. This can be overridden on a per-connection basis when editing a connection. By default, overall concurrent use of connections is unlimited ("0").
`MYSQL_DEFAULT_MAX_GROUP_CONNECTIONS`	The maximum number of concurrent connections to allow to any one Guacamole connection group. If set to "0", this will be unlimited. This can be overridden on a per-group basis when editing a connection group. By default, overall concurrent use of connection groups is unlimited ("0").
`MYSQL_DEFAULT_MAX_CONNECTIONS_PER_USER`	The maximum number of concurrent connections to allow a single user to maintain to any one Guacamole connection. If set to "0", this will be unlimited. This can be overridden on a per-connection basis when editing a connection. By default, per-user concurrent use of connections is unlimited ("0").
`MYSQL_DEFAULT_MAX_GROUP_CONNECTIONS_PER_USER`	The maximum number of concurrent connections to allow a single user to maintain to any one Guacamole connection group. If set to "0", this will be unlimited. This can be overridden on a per-group basis when editing a connection group. By default, per-user concurrent use of connection groups is limited to one ("1"), to prevent a balancing connection group from being completely exhausted by one user alone.

PostgreSQL authentication

To use Guacamole with the PostgreSQL authentication backend, you will need either a Docker container running the postgres image, or network access to a working installation of PostgreSQL. The connection to PostgreSQL can be specified using either environment variables or a Docker link.

Initializing the PostgreSQL database

To generate a SQL script which can be used to initialize a fresh PostgreSQL database as documented in Chapter 6, Database authentication:

$ docker run --rm guacamole/guacamole /opt/guacamole/bin/initdb.sh --postgres > initdb.sql

Alternatively, you can use the SQL scripts included with the database authentication.

Once this script is generated, you must:

Create a database for Guacamole within PostgreSQL, such as guacamole_db.
Run the script on the newly-created database.
Create a user for Guacamole within PostgreSQL with access to the tables and sequences of this database, such as guacamole_user.

The process for doing this via the psql and createdb utilities included with PostgreSQL is documented in Chapter 6, Database authentication.

Connecting Guacamole to PostgreSQL

If your PostgreSQL database is provided by another Docker container, and you wish to use a Docker link to connect the Guacamole image to your database, the connection details are implied by the Docker link itself:

$ docker run --name some-guacamole \
    --link some-guacd:guacd         \
    --link some-postgres:postgres  \
    ...
    -d -p 8080:8080 guacamole/guacamole

If you are not using Docker to provide your PostgreSQL database, you will need to provide the network connection information yourself using additional environment variables:

Variable	Description
`POSTGRES_HOSTNAME`	The hostname of the database to use for Guacamole authentication. This is required if you are not using Docker to provide your PostgreSQL database.
`POSTGRES_PORT`	The port that Guacamole should use when connecting to PostgreSQL. This environment variable is optional. If not provided, the standard PostgreSQL port of 5432 will be used.

The POSTGRES_HOSTNAME and, if necessary, POSTGRES_PORT environment variables can thus be used in place of a Docker link if using a Docker link is impossible or undesirable:

$ docker run --name some-guacamole   \
    --link some-guacd:guacd           \
    -e POSTGRES_HOSTNAME=172.17.42.1 \
    ...
    -d -p 8080:8080 guacamole/guacamole

Note that a Docker link to guacd (the --link some-guacd:guacd option above) is not required any more than a Docker link is required for PostgreSQL. The connection information for guacd can be specified using environment variables, as described in the section called “Connecting Guacamole to guacd”.

Required environment variables

Using PostgreSQL for authentication requires additional configuration parameters specified via environment variables. These variables collectively describe how Guacamole will connect to PostgreSQL:

Variable	Description
`POSTGRES_DATABASE`	The name of the database to use for Guacamole authentication.
`POSTGRES_USER`	The user that Guacamole will use to connect to PostgreSQL.
`POSTGRES_PASSWORD`	The password that Guacamole will provide when connecting to PostgreSQL as `POSTGRES_USER`.

Optional environment variables

Variable	Description
`POSTGRES_ABSOLUTE_MAX_CONNECTIONS`	The absolute maximum number of concurrent connections to allow at any time, regardless of the Guacamole connection or user involved. If set to "0", this will be unlimited. Because this limit applies across all Guacamole connections, it cannot be overridden if set. By default, the absolute total number of concurrent connections is unlimited ("0").
`POSTGRES_DEFAULT_MAX_CONNECTIONS`	The maximum number of concurrent connections to allow to any one Guacamole connection. If set to "0", this will be unlimited. This can be overridden on a per-connection basis when editing a connection. By default, overall concurrent use of connections is unlimited ("0").
`POSTGRES_DEFAULT_MAX_GROUP_CONNECTIONS`	The maximum number of concurrent connections to allow to any one Guacamole connection group. If set to "0", this will be unlimited. This can be overridden on a per-group basis when editing a connection group. By default, overall concurrent use of connection groups is unlimited ("0").
`POSTGRES_DEFAULT_MAX_CONNECTIONS_PER_USER`	The maximum number of concurrent connections to allow a single user to maintain to any one Guacamole connection. If set to "0", this will be unlimited. This can be overridden on a per-connection basis when editing a connection. By default, per-user concurrent use of connections is unlimited ("0").
`POSTGRES_DEFAULT_MAX_GROUP_CONNECTIONS_PER_USER`	The maximum number of concurrent connections to allow a single user to maintain to any one Guacamole connection group. If set to "0", this will be unlimited. This can be overridden on a per-group basis when editing a connection group. By default, per-user concurrent use of connection groups is limited to one ("1"), to prevent a balancing connection group from being completely exhausted by one user alone.

LDAP authentication

To use Guacamole with the LDAP authentication backend, you will need network access to an LDAP directory. Unlike MySQL and PostgreSQL, the Guacamole Docker image does support Docker links for LDAP; the connection information must be specified using environment variables:

Variable	Description
`LDAP_HOSTNAME`	The hostname or IP address of your LDAP server.
`LDAP_PORT`	The port your LDAP server listens on. By default, this will be 389 for unencrypted LDAP or LDAP using STARTTLS, and 636 for LDAP over SSL (LDAPS).
`LDAP_ENCRYPTION_METHOD`	The encryption mechanism that Guacamole should use when communicating with your LDAP server. Legal values are "none" for unencrypted LDAP, "ssl" for LDAP over SSL/TLS (commonly known as LDAPS), or "starttls" for STARTTLS. If omitted, encryption will not be used.

Only the LDAP_HOSTNAME variable is required, but you may also need to specify LDAP_PORT or LDAP_ENCRYPTION_METHOD if your LDAP directory uses encryption or listens on a non-standard port:

$ docker run --name some-guacamole \
    --link some-guacd:guacd         \
    -e LDAP_HOSTNAME=172.17.42.1   \
    ...
    -d -p 8080:8080 guacamole/guacamole

Note that a Docker link to guacd (the --link some-guacd:guacd option above) is not required. Similar to LDAP, the connection information for guacd can be specified using environment variables, as described in the section called “Connecting Guacamole to guacd”.

Required environment variables

Using LDAP for authentication requires additional configuration parameters specified via environment variables. These variables collectively describe how Guacamole will query your LDAP directory:

Variable	Description
`LDAP_USER_BASE_DN`	The base of the DN for all Guacamole users. All Guacamole users that will be authenticating against LDAP must be descendents of this base DN.

As with the other authentication mechanisms, if any required environment variables are omitted (including those required for connecting to the LDAP directory over the network), you will receive an error message in the logs, and the image will stop. You will then need to recreate the container with the proper variables specified.

Optional environment variables

Additional optional environment variables may be used to configure the details of your LDAP directory hierarchy, or to enable more flexible searching for user accounts:

Variable	Description
`LDAP_GROUP_BASE_DN`	The base of the DN for all groups that may be referenced within Guacamole configurations using the standard seeAlso attribute. All groups which will be used to control access to Guacamole configurations must be descendents of this base DN. If this variable is omitted, the seeAlso attribute will have no effect on Guacamole configurations.
`LDAP_SEARCH_BIND_DN`	The DN (Distinguished Name) of the user to bind as when authenticating users that are attempting to log in. If specified, Guacamole will query the LDAP directory to determine the DN of each user that logs in. If omitted, each user's DN will be derived directly using the base DN specified with `LDAP_USER_BASE_DN`.
`LDAP_SEARCH_BIND_PASSWORD`	The password to provide to the LDAP server when binding as `LDAP_SEARCH_BIND_DN` to authenticate other users. This variable is only used if `LDAP_SEARCH_BIND_DN` is specified. If omitted, but `LDAP_SEARCH_BIND_DN` is specified, Guacamole will attempt to bind with the LDAP server without a password.
`LDAP_USERNAME_ATTRIBUTE`	The attribute or attributes which contain the username within all Guacamole user objects in the LDAP directory. Usually, and by default, this will simply be "uid". If your LDAP directory contains users whose usernames are dictated by different attributes, multiple attributes can be specified here, separated by commas, but beware: doing so requires that a search DN be provided with `LDAP_SEARCH_BIND_DN`.
`LDAP_CONFIG_BASE_DN`	The base of the DN for all Guacamole configurations. If omitted, the configurations of Guacamole connections will simply not be queried from the LDAP directory, and you will need to store them elsewhere, such as within a MySQL or PostgreSQL database.

As documented in Chapter 7, LDAP authentication, Guacamole does support combining LDAP with a MySQL or PostgreSQL database, and this can be configured with the Guacamole Docker image, as well. Each of these authentication mechanisms is independently configurable using their respective environment variables, and by providing the required environment variables for multiple systems, Guacamole will automatically be configured to use each when the Docker image starts.

Custom extensions and `GUACAMOLE_HOME`

If you have your own or third-party extensions for Guacamole which are not supported by the Guacamole Docker image, but are compatible with the version of Guacamole within the image, you can still use them by providing a custom base configuration using the GUACAMOLE_HOME environment variable:

Variable	Description
`GUACAMOLE_HOME`	The absolute path to the directory within the Docker container to use as a template for the image's automatically-generated `GUACAMOLE_HOME`. Any configuration generated by the Guacamole Docker image based on other environment variables will be applied to an independent copy of the contents of this directory.

You will still need to follow the steps required to create the contents of GUACAMOLE_HOME specific to your extension (placing the extension itself within GUACAMOLE_HOME/extensions/, adding any properties to guacamole.properties, etc.), but the rest of Guacamole's configuration will be handled automatically, overlaid on top of a copy of the GUACAMOLE_HOME you provide.

Because the Docker image's GUACAMOLE_HOME environment variable must point to a directory within the container, you will need to expose your custom GUACAMOLE_HOME to the container using the -v option of docker run. The container directory chosen can then be referenced in the GUACAMOLE_HOME environment variable, and the image will handle the rest automatically:

$ docker run --name some-guacamole    \
    ...
    -v /local/path:/some-directory   \
    -e GUACAMOLE_HOME=/some-directory \
    -d -p 8080:8080 guacamole/guacamole

Verifying the Guacamole install

Once the Guacamole image is running, Guacamole should be accessible at http://HOSTNAME:8080/guacamole/, where HOSTNAME is the hostname or address of the machine hosting Docker, and you should a login screen. If using MySQL or PostgreSQL, the database initialization scripts will have created a default administrative user called "guacadmin" with the password "guacadmin". You should log in and change your password immediately. If using LDAP, you should be able to log in as any valid user within your LDAP directory.

If you cannot access Guacamole, or you do not see a login screen, check Docker's logs using the docker logs command to determine if something is wrong. Configuration parameters may have been given incorrectly, or the database may be improperly initialized:

$ docker logs some-guacamole

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