Patching is a critical security service that keeps computer systems up to date and defends against security threats. Existing patching systems all require running systems. With the increasing adoption of virtualization and cloud computing services, there is a growing number of dormant virtual machine (VM) images. Such VM images cannot benefit from existing patching systems, and thus are often left vulnerable to emerging security threats. It is possible to bring VM images online, apply patches, and capture the VMs back to dormant images. However, such approaches suffer from unpredictability, performance challenges, and high operational costs, particularly in large-scale compute clouds where there could be thousands of dormant VM images.   This paper presents a novel tool named  Nuwa  that enables efficient and scalable offline patching of dormant VM images. Nuwa analyzes patches and, when possible, converts them into patches that can be applied offline by rewriting the patching scripts. Nuwa also leverages the VM image manipulation technologies offered by the Mirage image library to provide an efficient and scalable way to patch VM images in batch. Nuwa has been evaluated on freshly built images and on real-world images from the IBM Research Compute Cloud (RC2), a compute cloud used by IBM researchers worldwide. When applying security patches to a fresh installation of Ubuntu-8.04, Nuwa successfully applies 402 of 406 patches. It speeds up the patching process by more than 4 times compared to the online approach and by another 2--10 times when integrated with Mirage. Nuwa also successfully applies the 10 latest security updates to all VM images in RC2.
['Wu Zhou', 'Peng Ning', 'Xiaolan Zhang', 'Glenn Ammons', 'Ruowen Wang', 'Vasanth Bala']
Always up-to-date: scalable offline patching of VM images in a compute cloud