Proxmox Cloud-Init OS template creation

Introduction

In this guide we will go over creating a Proxmox KVM Template from a Cloud Image. This same process will work for any Cloud-Init Openstack based image type you can find online.

Having done a number of these for our Proxmox based VPS service I wanted to post up a guide to help anyone else looking to do the same thing.

My workflow for customizing one of those for use with Proxmox with cloud-init deployment from WHMCS and root login is below. Once you setup one template you can rapidly reinstall new containers and test stuff.

Setup Environment

If not installed already installed you will need libguestfs-tools :

apt-get install libguestfs-tools

To edit the image before importing. We will use virt-edit which is a part of libguestfs-tools.

For the sake of sanity, I highly advise setting your default editor to “nano” because using the default libguestfs-tools editor is a really frustrating experience to learn and will save a lot of wasted time and errors.

You can see your default editor with the the below command.

printenv | grep EDITOR

To set nano as default if it’s not already. use the below command. Please Note: nano should be installed(should be by default on Ubuntu/Debian systems)

export EDITOR=nano

It should now look like the below.

root@coby:~# printenv | grep EDITOR
EDITOR=/bin/nano
root@coby:~#

Grab the Cloud Image
Grab the cloud image base link for desired OS: Openstack has a nice page on this: https://docs.openstack.org/image-guide/obtain-images.html

These are some direct links:

https://cloud.centos.org/centos/7/images/
https://cloud-images.ubuntu.com/

Ssh into your Proxmox server and fetch the image directly to the server. This saves you having to upload it to the server later. Im grabbing latest Centos 7 for this guide.

wget https://cloud.centos.org/centos/7/images/CentOS-7-x86_64-GenericCloud-1907.qcow2

Customize Image
We can now use virt-edit to edit the image to enable our desired defaults. The modifications below allows root and password-based logins. Not being able to login to the VPS in novnc without a password is a real pain when trying to fix a network-related issue with the template and it’s locked to key-based.

Here is the format for the command.

virt-edit -a Cloudimagefilename /path/to/file/in/disk/image/cloud.cfg

So for our example of “CentOS-7-x86_64-GenericCloud-1907.qcow2” to open up the “/etc/cloud/cloud.cfg” so we can modify it to enable root and password logins. The below command will be used. Note it may take a second to open so be patient.

virt-edit -a CentOS-7-x86_64-GenericCloud-1907.qcow2 /etc/cloud/cloud.cfg

Once opened it will look something like this.

The first thing you want to do is carefully edit the disable_root: 1 to disable_root: 0 This will set cloud-init to not disable this in the /etc/ssh/sshd_config on first boot and allow root based logins. It should look like the below.

Please note some OS cloud images use “true” or “false” where 1=true and 0=false. If they are using true and false vs 1 and 0 please use that formatting.

Next we need to toggle the “lock_passwd” from “true” to “false” Without this you will be unable to use password-based authentication for the account. Scroll down towards the bottom of the file and look for the default user section. See below.

Once fixed it will look like this.

Next part is optional and would go in this same file. I find it handy to splice in the qemu-guest-agent and other stuff I want to be installed right out of the box for the template. The formatting is crucial so make sure you copy it and maintain the yaml formatting that cloud-init config file is based on.

packages:
- qemu-guest-agent
- nano
- wget
- curl
- net-tools

Should look like this. Sometimes I have to put this packages above the ssh_svcname: sshd block for some OS. So if it doesn’t work insert it above that block. See the cloud-init documentation for more details.

Now you can use ctrl+x and hit y to save and exit.

Modify the sshd_config

Now we need to ensure the default /etc/ssh/sshd_config is setup to our liking and allows root login. We need to ensure the below values are set.

PermitRootLogin yes
PasswordAuthentication yes

So now we reopen the image but this time were editing the file “/etc/ssh/sshd_config”

virt-edit -a CentOS-7-x86_64-GenericCloud-1907.qcow2 /etc/ssh/sshd_config

Now we need to look for “PermitRootLogin” it may be commented out or set to “PermitRootLogin no” or “PermitRootLogin without-password”. make sure only one occurrence is enabled and it says “PermitRootLogin yes” like the below example.

Now we will scroll down and verify that “PasswordAuthentication yes” is set. Sometimes it is sometimes it isn’t so always check. In this template it was enabled. So we can save and close this now if no other customizations are needed.

Editing existing images of imported images
Occasionally you will find you got everything except one thing working and you want to modify the image of existing VM. This is totally possible just ensure that the guest VM is completely powered off first.

To edit an already imported disk. This example is based on the vm with id 104. You may need to verify the full path to the disk as the disk image name may vary depending on your environment.

virt-edit -a /var/lib/vz/images/104/vm-104-disk-0.raw /etc/cloud/cloud.cfg

Creating VM

Here we are going to tie it all together.

Create the VM: See the official link > https://pve.proxmox.com/wiki/Cloud-Init_Support

You may need to create the container if it does not exist already. The below is based on my storage for OS template VM using “local” storage yours may be “zfs” or “local-lvm” etc so may need to update those paths to suit your environment.

Create a new VM

qm create 9000 --memory 2048 --net0 virtio,bridge=vmbr0

Import the downloaded disk to local storage

qm importdisk 9000 CentOS-7-x86_64-GenericCloud-1907.qcow2 local

Finally attach the new disk to the VM as scsi drive

qm set 9000 --scsihw virtio-scsi-pci --scsi0 local:vm-9000-disk-1

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

qm set 9000 --ide2 local: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 CDROM.

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

Create a clone from the previous template.

qm clone 9000 123 --name Centos-7-Minimal

Conclusion
I hope you found this tutorial helpful in creating a Proxmox cloud-init KVM template. There is so much more you can do with cloud-init and libguestfs-tools like injecting apps and repos in the image before its even booted. We recommend making backups before major edits so you can revert back to the base image if there is an issue.

Resource and reference links.

Proxmox Cloud-Init OS template creation


https://pve.proxmox.com/wiki/Cloud-Init_Support
https://docs.openstack.org/image-guide/modify-images.html
http://libguestfs.org/virt-edit.1.html

Linux KVM/Qemu Virt-Customize Tutorial


virt-customize –run-command ‘yum -y install network-scripts traceroute atop sysstat’ -a /var/lib/vz/images/104/vm-104-disk-0.raw

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