Update cloudinit.md

cloudinit.md

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 # CloudInit
 
+> CloudInit support is available from 4.11 release
+
+Cloud-init is a program "that handles early initialization of a cloud instance"[^n]. In other words, you can, on a "cloud-init"-ready template VM, pass a lot of data at first boot:
+
+* setting hostname
+* add ssh keys
+* grow automatically the file system
+* create users
+* and a lot more!
+
+This tool is pretty standard and used everywhere. A lot of existing cloud templates are using it.
+
+So it means customizing very easily your VM when you create it from a compatible template. It brings you closer to the "instance" principle, like in Amazon cloud or OpenStack.
+
+## Requirement
+
+You only need to use a template of a VM with CloudInit installed inside it.
+
+## Usage
+
+First, select your compatible template (CloudInit ready) and name it:
+
+![](https://xen-orchestra.com/blog/content/images/2015/12/template_choice.png)
+
+Then, activate the config drive and put your SSH key:
+
+![](https://xen-orchestra.com/blog/content/images/2015/12/sshkey.png)
+
+You can extend the disk size (**in this case, the template disk was 8 GiB originally**):
+
+![](https://xen-orchestra.com/blog/content/images/2015/12/diskedition.png)
+
+Finally, create the VM:
+
+![](https://xen-orchestra.com/blog/content/images/2015/12/recap.png)
+
+Now start the VM and SSH on its IP:
+
+* **the system got the right VM hostname** (from VM name) 
+* you don't have to use a password to access it (thanks to your SSH key):
+
+```
+$ ssh centos@192.168.100.226
+[centos@tmp-app1 ~]$ 
+```
+
+The default `cloud-init` configuration could allow you to be to be a sudoer directly:
+
+```
+[centos@tmp-app1 ~]$ sudo -s
+[root@tmp-app1 centos]# 
+```
+
+Check the root file system size: indeed, **it was automatically grown** to what you need:
+
+```
+[centos@tmp-app1 ~]$ df -h
+/dev/xvda1          20G    1,2G   18G   6% /
+```