To send or download data in image-based formats, such as PNG or PDF files, and to use features such as Paper size and Expand tables, Looker requires rendering software. This page explains how to install rendering software on a customer-hosted instance of Looker.
Installing Rendering Software to Run Standard Looker Features
The following software needs to be installed to use some Looker features.
When scheduling or sending Looks and dashboards, Chromium is required to render these data formats:
- For dashboards: PDF, Visualization
- For Looks: Visualization, HTML
When downloading data, Chromium is required to render these data formats:
- For dashboards: PDF
- For Looks: HTML, PNG (Image of Visualization)
The Chromium Project is an open source project started by Google to share the non-proprietary parts of Google Chrome.
If you have a Looker-hosted instance, this software is already installed. If you have a customer-hosted Looker instance, follow the instructions below.
Currently, Chromium is best supported on Ubuntu systems, but we also provide installation instructions for Debian and Amazon Linux. Make sure you install Chromium into an executable path on the machine that hosts the Looker instance. The Looker application needs to access Chromium using the
chromium command or via a custom path set with the
CHROMIUM_PATH environment variable.
Chromium 65 or later is required, but the latest version is generally recommended (Looker does not recommend installing Chromium 71 for use with a Looker instance). Chromium rendering will wait for all resources requested by the page to be completed before it sends the "finished" signal that prompts Looker to produce the rendered content. Due to the number and frequency of these resource requests, some networks can falsely flag the requests as malicious, causing them to drop, which will delay your rendered jobs.
If you are installing Chromium on a clustered Looker installation, the Chromium version on each node must be fully identical. Even minor differences, such as different build numbers, can interfere with Looker's rendering capabilities.
To install Chromium on Ubuntu:
sudocommand to perform these steps as the Looker user. Do not install Chromium when you are logged in as the root user. If you install Chromium while logged in as the root user, Looker might not be able to execute PDF or PNG rendering.
Fonts must be installed on the system for Chromium to start. You can install fonts using the command line interface. For example, this command installs the default fonts on Ubuntu 16.04 LTS:
$apt-get install fonts-freefont-otf
On the command line, enter the following command:
apt-get update && apt-get install -y chromium-browser
Ubuntu may need to either alias
chromiumor export the environment variable. To alias
chromium, place the following in the
To make this alias known to Looker, run this command on the command line:
sudo ln -s /usr/bin/chromium-browser /usr/bin/chromium
After setting any environment variables, restart the Looker application for them to take effect. You may also need to restart any open terminal sessions, or run
source ~/.bash_profileto get the terminal to read the new configuration.
After installing Chromium you should get a valid response from either
$CHROMIUM_PATH --versiondepending on whether you set the environment variable.
Optional Environment Variables:
CHROMIUM_PATH: Path to the Chromium binary, defaults to
CHROMIUM_PID_DIR: Path to where the library can store Chromium PID files, defaults to
chromium_pid_filesin the Looker application's working directory.
CHROMIUM_PORT_RANGE_END: The Chromium application needs a range of ports to communicate between processes on the local machine. The default range is 40000-40500 but you can override this default by setting both of these environment variables. Unused ports are selected at random from the range and are only used for the duration of a single render.