How to add ssh key to qcow2 Linux cloud images using virt-sysprep
I
have installed and setup KVM server on an Ubuntu Linux. I downloaded various .qcow2 cloud images. How do I setup public ssh keys for downloaded CentOS/FreeBSD/Ubuntu cloud images using virt-sysprep?
You need to use a command called virt-sysprep that lets you reset or unconfigure virtual machines in preparation for cloning them.
Step 1: Install virt-sysprep
Type the following apt-get command/apt command to install virt-sysprep on a Debian or Ubuntu Linux:
$ sudo apt install libguestfs-tools
If you are using a CentOS/RHEL/Oracle/Scientific Linux, type the following yum command:
$ sudo yum install libguestfs-tools
If you are using a Fedora Linux, type the following dnf command to install the same:
$ sudo dnf install libguestfs-tools
Step 2: Download cloud image in .qcow2 format
You can grab cloud images from the following sites (grab the file ending with .qcow2/.qcow2.xz extensions):
CentOS 7
CentOS 6.x
Debian 8.x
Debian 9.x
Fedora 26
Ubuntu 16.04 LTS
FreeBSD 11.x
openSUSE/SLES
AWS Linux
RHEL 7 (subscription only)
RHEL 6(subscription only)
SLES(subscription only)
For demo purpose I am downloading and using CentOS 7 image using wget command:
$ wget https://cloud.centos.org/centos/7/images/CentOS-7-x86_64-GenericCloud.qcow2.xz
Use xz command for decompression:
$ xz -v -d CentOS-7-x86_64-GenericCloud.qcow2.xz
Step 3: Setup/inject an ssh keys
To inject an ssh key so the given “USER” will be able to log in over ssh without supplying a password. The “USER” must exist already in the guest. For CentOS 7 user name is centos:
$ sudo virt-sysprep -a CentOS-7-x86_64-GenericCloud.qcow2 \
–ssh-inject centos:file:/home/vivek/.ssh/id_rsa.pub
Where,
–ssh-inject centos:file:/home/vivek/.ssh/id_rsa.pub : Read the ssh key from id_rsa.pub.
It is also possible to create a new user named vivek and add ssh-key as follows:
$ sudo virt-sysprep -a CentOS-7-x86_64-GenericCloud.qcow2 \
–run-command useradd vivek \
–ssh-inject vivek:file:/home/vivek/.ssh/id_rsa.pub
Sample outputs:
Adding SSH key to Linux KVM cloud user vivek using virt-sysprep
Step 4: Launch a new VM using CentOS-7-x86_64-GenericCloud-1503.qcow2 image
The syntax is:
$ virt-install –import \
–name centos7-vm1 \
–memory 1024 \
–vcpus 2 \
–cpu host \
–disk path=/var/lib/libvirt/images/centos7.qcow2,size=10,bus=virtio,format=qcow \
–os-type=linux \
–os-variant=centos7.0 \
–graphics spice \
–noautoconsole \
–disk /home/vivek/modifyisoimages/CentOS-7-x86_64-GenericCloud.qcow2
Step 5: Test it with ssh
To find out your vm’s IP address run:
$ virsh net-list
$ virsh net-dhcp-leases default
To login using ssh command:
$ ssh vivek@vms-ip-address-here
Other options to set ssh key for your cloud images
Use uvt-kvm on a Ubuntu Linux to setup ssh-keys for cloud image.
Use cloudinit to setup ssh keys
Also read virt-sysprep man page.
