cloud init: add warning to not install cloud-init on the host

[pve-docs.git] / qm-cloud-init.adoc

[[qm_cloud_init]]
Cloud-Init Support
------------------
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https://cloudinit.readthedocs.io[Cloud-Init] is the de facto
multi-distribution package that handles early initialization of a
virtual machine instance. Using Cloud-Init, configuration of network
devices and ssh keys on the hypervisor side is possible. When the VM
starts for the first time, the Cloud-Init software inside the VM will
apply those settings.

Many Linux distributions provide ready-to-use Cloud-Init images, mostly
designed for 'OpenStack'. These images will also work with {pve}. While
it may seem convenient to get such ready-to-use images, we usually
recommended to prepare the images by yourself. The advantage is that you
will know exactly what you have installed, and this helps you later to
easily customize the image for your needs.

Once you have created such a Cloud-Init image we recommend to convert it
into a VM template. From a VM template you can quickly create linked
clones, so this is a fast method to roll out new VM instances. You just
need to configure the network (and maybe the ssh keys) before you start
the new VM.

We recommend using SSH key-based authentication to login to the VMs
provisioned by Cloud-Init. It is also possible to set a password, but
this is not as safe as using SSH key-based authentication because {pve}
needs to store an encrypted version of that password inside the
Cloud-Init data.

{pve} generates an ISO image to pass the Cloud-Init data to the VM. For
that purpose, all Cloud-Init VMs need to have an assigned CD-ROM drive.
Also many Cloud-Init images assume to have a serial console, so it is
recommended to add a serial console and use it as display for those VMs.


Preparing Cloud-Init Templates
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The first step is to prepare your VM. Basically you can use any VM.
Simply install the Cloud-Init packages inside the VM that you want to
prepare. On Debian/Ubuntu based systems this is as simple as:

----
apt-get install cloud-init
----

WARNING: This command is *not* intended to be executed on the {pve} host, but
only inside the VM.

Already many distributions provide ready-to-use Cloud-Init images (provided
as `.qcow2` files), so alternatively you can simply download and
import such images. For the following example, we will use the cloud
image provided by Ubuntu at https://cloud-images.ubuntu.com.

----
# download the image
wget https://cloud-images.ubuntu.com/bionic/current/bionic-server-cloudimg-amd64.img

# create a new VM
qm create 9000 --memory 2048 --net0 virtio,bridge=vmbr0

# import the downloaded disk to local-lvm storage
qm importdisk 9000 bionic-server-cloudimg-amd64.img local-lvm

# finally attach the new disk to the VM as scsi drive
qm set 9000 --scsihw virtio-scsi-pci --scsi0 local-lvm:vm-9000-disk-1
----

NOTE: Ubuntu Cloud-Init images require the `virtio-scsi-pci`
controller type for SCSI drives.

.Add Cloud-Init CD-ROM drive

[thumbnail="screenshot/gui-cloudinit-hardware.png"]

The next step is to configure a CD-ROM drive, which will be used to pass
the Cloud-Init data to the VM.

----
qm set 9000 --ide2 local-lvm:cloudinit
----

To be able to boot directly from the Cloud-Init image, set the
`bootdisk` parameter to `scsi0`, and restrict BIOS to boot from disk
only. This will speed up booting, because VM BIOS skips the testing for
a bootable CD-ROM.

----
qm set 9000 --boot c --bootdisk scsi0
----

Also configure a serial console and use it as a display. Many Cloud-Init
images rely on this, as it is an requirement for OpenStack images.

----
qm set 9000 --serial0 socket --vga serial0
----

In a last step, it is helpful to convert the VM into a template. From
this template you can then quickly create linked clones.
The deployment from VM templates is much faster than creating a full
clone (copy).
----
qm template 9000
----


Deploying Cloud-Init Templates
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[thumbnail="screenshot/gui-cloudinit-config.png"]

You can easily deploy such a template by cloning:

----
qm clone 9000 123 --name ubuntu2
----

Then configure the SSH public key used for authentication, and configure
the IP setup:

----
qm set 123 --sshkey ~/.ssh/id_rsa.pub
qm set 123 --ipconfig0 ip=10.0.10.123/24,gw=10.0.10.1
----

You can also configure all the Cloud-Init options using a single command
only. We have simply split the above example to separate the
commands for reducing the line length. Also make sure to adopt the IP
setup for your specific environment.


Custom Cloud-Init Configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The Cloud-Init integration also allows custom config files to be used instead
of the automatically generated configs. This is done via the `cicustom`
option on the command line:

----
qm set 9000 --cicustom "user=<volume>,network=<volume>,meta=<volume>"
----

The custom config files have to be on a storage that supports snippets and have
to be available on all nodes the VM is going to be migrated to. Otherwise the
VM won't be able to start.
For example:

----
qm set 9000 --cicustom "user=local:snippets/userconfig.yaml"
----

There are three kinds of configs for Cloud-Init. The first one is the `user`
config as seen in the example above. The second is the `network` config and
the third the `meta` config. They can all be specified together or mixed
and matched however needed.
The automatically generated config will be used for any that don't have a
custom config file specified.

The generated config can be dumped to serve as a base for custom configs:

----
qm cloudinit dump 9000 user
----

The same command exists for `network` and `meta`.


Cloud-Init specific Options
~~~~~~~~~~~~~~~~~~~~~~~~~~~

include::qm-cloud-init-opts.adoc[]


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See Also
~~~~~~~~

* link:/wiki/Qemu/KVM_Virtual_Machines[Qemu/KVM Virtual Machines]

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