Cloud-init scripts let you optionally automate the initialization of virtual machines.
Setting a cloud-init script
To set a cloud-init script, click on the "Click for more advanced options" green link when deploying your virtual machine.
Click on the "Click for more advanced options" green link to show this textarea
This is the default cloudinit configuration we pass to the hypervisor:
The script that you provide simply gets appended to the end of this file.
Examples
Example 1: Preventing the automatic update of NVIDIA drivers
NVIDIA drivers autoupdate on the first boot. Once this happens, they become unusable. By including this cloud-init script, you'll lock the NVIDIA driver versions so that they do not autoupdate
Objectives
Write a file using cloud-init write_files in base64 encoding that uses apt-mark to hold NVIDIA packages from being automatically updated
The file will have the following contents:
dpkg-query -W --showformat='${Package} ${Status}\n' | grep -v deinstall | awk '{ print $1 }' | grep -E 'nvidia.*-[0-9]+$' | xargs -r -L 1 apt-mark hold
First, our server will write the new file, prevent_update.sh, in the user's new tensordock_scripts directory
Then, our server run this file, locking in our NVIDIA driver versions to prevent autoupdates
Example 2: Hosting a website with Apache2
Objectives
Install a package through cloud-init packages
Write a file using cloud-init write_files in plaintext
Process
By default, the Apache2 webserver listens on port 80. As such, we'll first forward an external port into that internal port.
Because Apache listens on port 80, you'll want to forward an external port into that internal port
Then, we'll set this as our cloud-init script:
Note the indentation of the custom HTML we've defined above! When writing files, we must append four (4) spaces in front of each text block.
Debrief
Explanation:
First, our server will install the apache2 package
Then, our server will overwrite the we create an index.html file with the custom HTML we've defined
Now, let's try accessing our web server!
Woohoo! It works!
Example 3: Hosting a simple Docker container
Objectives
Host a simple Docker container through the Docker CLI
TensorDock operating system templates come preinstalled with Docker
Process
For networking, we forward an external port into an internal port in the virtual machine. Then, a Docker container forwards a virtual machine's port into its own internal network.
By default, the NGINX webserver listens on port 80 within the Docker container, but we can have the Docker container listen on any port. As such, we'll first forward an external port (e.g. 20018) into itself.
We'll forward an external port into an internal port on the virtual machine
Then, we'll set this as our cloud-init script:
Note that we have our Docker container listen on port 20018 because we forwarded external port 20018 into the virtual machine on port 20018
Debrief
Explanation:
First, our server will write a file to a new directory containing our custom HTML
Then, our server will run a Docker container that passes through the directory of our HTML page into the NGINX contiainer
When users access the external port 20018, our hypervisor forwards that to the virtual machine's port 20018, and then Docker forwards that to the NGINX container on port 80
