305-300 LPIC-3: Virtualization and Containerization - Exam 305, version 3.0 Questions and Answers

Capabilities are a way of implementing fine-grained access control in Linux. They are a set of flags that define the privileges that a process can have. By default, a process inherits the capabilities of its parent, but some capabilities can be dropped or added by the process itself or by the kernel. In the context of container virtualization, capabilities are used to prevent processes from performing actions that might infringe the container, such as accessing the host’s devices, mounting filesystems, changing the system time, or killing other processes. Capabilities allow containers to run with a reduced set of privileges, enhancing the security and isolation of the container environment. For example, Docker uses a default set of capabilities that are granted to the processes running inside a container, and allows users to add or drop capabilities as needed12. References:

• Capabilities | Docker Documentation1
• Linux Capabilities: Making Them Work in Containers2

The type attribute of a element in a libvirt domain definition specifies the hypervisor used for running the domain. The allowed values are driver specific, but include “xen”, “kvm”, “hvf” (since 8.1.0 and QEMU 2.12), “qemu” and "lxc"1. Therefore, the valid values among the options are C. kvm and E. lxc. KVM stands for Kernel-based Virtual Machine, which is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V)2. LXC stands for Linux Containers, which is an operating system-level virtualization method for running multiple isolated Linux systems (containers) on a single control host3. The other options are not valid values for the type attribute, asthey are either not hypervisors or not supported by libvirt. References:http://libvirt.org/formatdomain.html

https://libvirt.org/formatcaps.html

IaaS is a type of cloud computing service that offers essential compute, storage, and networking resources on demand, on a pay-as-you-go basis. IaaS is one of the four types of cloud services, along with software as a service (SaaS), platform as a service (PaaS), and serverless12. IaaS eliminates the need for enterprises to procure, configure, or manage infrastructure themselves, and they only pay for what they use23. Some examples of IaaS providers are Microsoft Azure, Google Cloud, and Amazon Web Services.

 The command vagrant init is used to initialize the current directory to be a Vagrant environment by creating an initial Vagrantfile if one does not already exist1. The Vagrantfile contains the configuration settings for the Vagrant box, such as the box name, box URL, network settings, synced folders, provisioners, etc. The command vagrant init does not execute any provisioning tool, start any box, install Vagrant on a Linux host, or download any box. Those actions are performed by other Vagrant commands, such as vagrant provision, vagrant up, vagrant install, and vagrant box add, respectively. References:

• 1: vagrant init - Command-Line Interface | Vagrant | HashiCorp Developer

• The purpose of the packer inspect subcommand is to display an overview of the configuration contained in a Packer template1. A Packer template is a file that defines the various components a Packer build requires, such as variables, sources, provisioners, and post-processors2. The packer inspect subcommand can help you quickly learn about a template without having to dive into the HCL (HashiCorp Configuration Language) itself1. The subcommand will tell you things like what variables a template accepts, the sources it defines, the provisioners it defines and the order they’ll run, and more1.
• The other options are not correct because:

 The correct command to move the libvirt domain web1 from the current host system to the host system host2 is virsh migrate web1 qemu+ssh://host2/system. This command uses the virsh migrate command, which initiates the live migration of a domain to another host1. The first argument is the name of the domain to migrate, which in this case is web1. The second argument is the destination URI, which specifies the connection to the remote host and the hypervisor to use2. In this case, the destination URI is qemu+ssh://host2/system, which means to use the QEMU driver and connect to host2 via SSH, and use the system instance of libvirtd3. The other options are incorrect because they either use invalid commands or arguments, such as node-update, pool-add, patch, or cp, or they do not specify the destination URI correctly. References:

https://balamuruhans.github.io/2019/01/09/kvm-migration-with-libvirt.html

http://libvirt.org/migration.html

The CPU flag that indicates the hardware virtualization capability on an AMD CPU is SVM. SVM stands for Secure Virtual Machine, and it is a feature of AMD processors that enables the CPU to run virtual machines with hardware assistance. SVM is also known as AMD-V, which is AMD’s brand name for its virtualization technology. SVM allows the CPU to support a hypervisor, which is a software layer that creates and manages virtual machines. A hypervisor can run multiple virtual machines on a single physical machine, each with its own operating system and applications. SVM improves the performance and security of virtual machines by allowing the CPU to directly execute privileged instructions and handle memory access, instead of relying on software emulation or binary translation. SVM also provides nested virtualization, which is the ability to run avirtual machine inside another virtual machine. To use SVM, the CPU must support it and the BIOS must enable it. The user can check if the CPU supports SVM by looking for the svm flag in the /proc/cpuinfo file or by using the lscpu command. The user can also use the virt-host-validate command to verify if the CPU and the BIOS are properly configured for hardware virtualization123. References:

• How to check if CPU supports hardware virtualization (VT technology)1
• Processor support - KVM3
• How to Enable Virtualization in BIOS for Intel and AMD4

 LXD supports the following network interface types for containers: macvlan, bridged, physical, sriov, and ovn1. Macvlan creates a virtual interface on the host that is connected to the same network as the parent interface2. Bridged connects the container to a network bridge that acts as a virtual switch3. Physical attaches the container to a physical network interface on the host2. Ipsec and wifi are not valid network interface types for LXD containers. References:

• 1: Bridge network - Canonical LXD documentation
• 2: How to create a network - Canonical LXD documentation
• 4: LXD containers and networking with static IP - Super User

 Nested page table extensions, such as Intel Extended Page Table (EPT) or AMD Rapid Virtualization Indexing (RVI), are hardware features that facilitate the virtualization of memory. They allow the CPU to perform the translation of guest virtual addresses to host physical addresses in a single step, without the need for software-managed shadow page tables. This reduces the overhead and complexity of memory management for virtual machines, and improves their performance and isolation. Nested page table extensions do not directly affect the virtualization of other hardware components, such as network interfaces, host bus adapters, hard disks, or IO cache.

References:

• Second Level Address Translation - Wikipedia
• c - What is use of extended page table? - Stack Overflow
• Hypervisor From Scratch – Part 4: Address Translation Using Extended …

The default path to the Docker daemon configuration file on Linux is /etc/docker/daemon.json. This file is a JSON file that contains the settings and options for the Docker daemon, which is the service that runs on the host operating system and manages the containers, images, networks, and other Docker resources. The /etc/docker/daemon.json file does not exist by default, but it can be created by the user to customize the Docker daemon behavior. The file can also be specified by using the --config-file flag when starting the Docker daemon. The file must be a valid JSON object and follow the syntax and structure of the dockerd reference docs12. References:

• Docker daemon configuration file - Medium3
• Docker daemon configuration overview | Docker Docs4
• docker daemon | Docker Docs5

Cloud-init is a tool that allows users to customize the configuration and behavior of cloud instances during the boot process. Cloud-init can process different kinds of data that are passed to the instance via user-data, which is a mechanism provided by various cloud providers to inject data into the instance. Among the kinds of data that cloud-init can process directly from user-data are:

• Shell scripts to execute: Cloud-init can execute user-data that is formatted as a shell script, starting with the #!/bin/sh or #!/bin/bash shebang. The script can contain any commands that are valid in the shell environment of the instance. The script is executed as the root user during the boot process12.
• Lists of URLs to import: Cloud-init can import user-data that is formatted as a list of URLs, separated by newlines. The URLs can point to any valid data source that cloud-init supports, such as shell scripts, cloud-config files, or include files. The URLs are fetched and processed by cloud-init in the order they appear in the list13.
• cloud-config declarations in YAML: Cloud-init can process user-data that is formatted as a cloud-config file, which is a YAML document that contains declarations for various cloud-init modules. The cloud-config file can specify various aspects of the instance configuration, such as hostname, users, packages, commands, services, and more. The cloud-config file must start with the #cloud-config header14.

The other kinds of data listed in the question are not directly processed by cloud-init from user-data. They are either not supported, not recommended, or require additional steps to be processed. These kinds of data are:

• ISO images to boot from: Cloud-init does not support booting from ISO images that are passed as user-data. ISO images are typically used to install an operating system on a physical or virtual machine, not to customize an existing cloud instance. To boot from an ISO image, the user would need to attach it as a secondary disk to the instance and configure the boot order accordingly5.
• Base64-encoded binary files to execute: Cloud-init does not recommend passing binary files as user-data, as they may not be compatible with the instance’s architecture or operating system. Base64-encoding does not change this fact, as it only converts the binary data into ASCII characters. To execute a binary file, the user would need to decode it and make it executable on the instance6.

References:

• User-Data Formats — cloud-init 22.1 documentation
• User-Data Scripts
• Include File
• Cloud Config
• How to Boot From ISO Image File Directly in Windows
• How to run a binary file as a command in the terminal?.

The output of xl list shows the state of the domains. The domain with ID 6, Ubuntu, has a state of “b—”. This means that the domain is blocked, which means it is idle or waiting for I/O.

https://xenbits.xen.org/docs/unstable/man/xl.1.html

QEMU can provide some network services in a user network, which is a mode of networking that does not require any administrator privilege to run. The user network uses the SLIRP TCP/IP emulator to create a virtual NAT’ted subnet, with a DHCP server started by QEMU that gives out IP addresses to the guest machines and puts the host on 10.0.2.21. QEMU can also provide a TFTP server in the user network, which can be used to boot the guest machines from a network image. The TFTP server can be configured with the -tftp option2. QEMU does not provide BGP, CIFS, or AppleTalk services in the user network. BGP is a routing protocol that is used to exchange routing information between autonomous systems on the Internet3. CIFS is a file-sharing protocol that is used to access files and printers on a network4. AppleTalk is a deprecated network protocol suite that was used by Apple devices5. These services require more advanced networking features than the user network can offer, such as bridging, routing, or tunneling.

References:

• Documentation/Networking - QEMU
• QEMU/Networking - Wikibooks, open books for an open world
• Border Gateway Protocol - Wikipedia
• Common Internet File System - Wikipedia
• AppleTalk - Wikipedia

Sysprep is a tool that removes all your personal account and security information, and then prepares the machine to be used as an image. It is supported by Windows and some Linux distributions. It can also remove drivers and other machine-specific settings. Sysprep is required when creating a managed image outside of a gallery in Azure

https://learn.microsoft.com/en-us/azure/virtual-machines/generalize

Resource management for full virtualization is the process of allocating and controlling the physical resources of the host system to the virtual machines running on it. The hypervisor is the software layer that performs this task, by providing each virtual machine with a virtual hardware of a defined capacity that limits the resources of the virtual machine. For example, the hypervisor can specify how many virtual CPUs, how much memory, and how much disk space each virtual machine can use. The hypervisor can also enforce resource isolation and prioritization among the virtual machines, to ensure that they do not interfere with each other or consume more resources than they are allowed to. The hypervisor cannot provide fine-grained limits to internal elements of the guest operating system, such as the number of processes, because the hypervisor does not have access to the internal state of the guest operating system. The guest operating system is responsible for managing its own resources within the virtual hardware provided by the hypervisor. For example, the guest operating system can create an arbitrary amount of network sockets, as long as it does not exceed the network bandwidth allocated by the hypervisor. Full virtualization can pose limits to virtual machines, and does not always assign the host system’s resources in a first-come-first-serve manner. The hypervisor can use various resource management techniques, such as reservation, limit, share, weight, and quota, to allocate and control the resources of the virtual machines. The hypervisor can also use resource scheduling algorithms, such as round-robin, fair-share, or priority-based, to distribute the resources among the virtual machines according to their needs and preferences. All processes created within the virtual machines are not transparently and equally scheduled in the host system for CPU and I/O usage. The hypervisor can use different scheduling policies, such as proportional-share, co-scheduling, or gang scheduling, to schedule the virtual CPUs of the virtual machines on the physical CPUs of the host system. The hypervisor can alsouse different I/O scheduling algorithms, such as deadline, anticipatory, or completely fair queuing, to schedule the I/O requests of the virtual machines on the physical I/O devices of the host system. The hypervisor can also use different resource accounting and monitoring mechanisms, such as cgroups, perf, or sar, to measure and report the resource consumption and performance of the virtual machines. References:

• Oracle VM VirtualBox: Features Overview
• Resource Management as an Enabling Technology for Virtualization - Oracle
• Introduction to virtualization and resource management in IaaS | Cloud Native Computing Foundation