How to test
cloud-init locally before deploying#
It’s very likely that you will want to test
cloud-init locally before
deploying it to the cloud. Fortunately, there are several different virtual
machines (VMs) and container tools that are ideal for this sort of local
In this guide, we will show how to use three of the most popular tools: Multipass, LXD and QEMU.
Multipass is a cross-platform tool for launching Ubuntu VMs across Linux, Windows, and macOS.
When a user launches a Multipass VM, user data can be passed by adding the
--cloud-init flag and the appropriate YAML file containing the user data:
$ multipass launch bionic --name test-vm --cloud-init userdata.yaml
Multipass will validate the YAML syntax of the cloud-config file before attempting to start the VM! A nice addition which saves time when you’re experimenting and launching instances with various cloud-configs.
Multipass only supports passing user data, and only as YAML cloud-config
files. Passing a script, a MIME archive, or any of the other user data formats
cloud-init supports will result in an error from the YAML syntax validator.
LXD offers a streamlined user experience for using Linux system containers. With LXD, a user can pass:
The following command initialises a container with user data:
$ lxc init ubuntu-daily:bionic test-container $ lxc config set test-container user.user-data - < userdata.yaml $ lxc start test-container
To avoid the extra commands this can also be done at launch:
$ lxc launch ubuntu-daily:bionic test-container --config=user.user-data="$(cat userdata.yaml)"
Finally, a profile can be set up with the specific data if you need to launch this multiple times:
$ lxc profile create dev-user-data $ lxc profile set dev-user-data user.user-data - < cloud-init-config.yaml $ lxc launch ubuntu-daily:bionic test-container -p default -p dev-user-data
The above examples all show how to pass user data. To pass other types of configuration data use the config option specified below:
See the LXD Instance Configuration docs for more info about configuration values or the LXD Custom Network Configuration document for more about custom network config.
The cloud-localds command from the cloud-utils package generates
a disk with user-supplied data. The
NoCloud datasouce allows users to
provide their own user data, metadata, or network configuration directly to
an instance without running a network service. This is helpful for launching
local cloud images with QEMU, for example.
The following is an example of creating the local disk using the cloud-localds command:
$ cat >user-data <<EOF #cloud-config password: password chpasswd: expire: False ssh_pwauth: True ssh_authorized_keys: - ssh-rsa AAAA...UlIsqdaO+w== EOF $ cloud-localds seed.img user-data
seed.img can then be passed along to a cloud image
cloud-init. Below is an example of passing the
$ qemu-system-x86_64 -m 1024 -net nic -net user \ -hda ubuntu-20.04-server-cloudimg-amd64.img \ -hdb seed.img
The now-booted image will allow for login using the password provided above.
For additional configuration, users can provide much more detailed configuration, including network configuration and metadata:
$ cloud-localds --network-config=network-config-v2.yaml \ seed.img userdata.yaml metadata.yaml
See the Networking config Version 2 page for details on the format and config of network configuration. To learn more about the possible values for metadata, check out the NoCloud page.