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
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:
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