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

Containerd is an industry-standard container runtime that uses Runc (a low-level container runtime) by default, but can be configured to use others as well1. Containerd manages the complete container lifecycle of its host system, from image transfer and storage to containerexecution and supervision1. It supports the standards established by the Open Container Initiative (OCI)1. Containerd does not require the Docker engine and Docker CLI to be installed, as it can be used independently or with other container platforms2. Containerd is not a text file format, nor does it run in each Docker container or provide DHCP client functionality. Containerd is not the initial process run at the start of any Docker container, as that is the role of the container runtime, such as Runc3. References: 1 (search for “containerd”), 2 (search for “Containerd is an open source”), 3 (search for “It uses rune to start containers”).

The lxc-attach command allows the user to start a new process within a running LXC container12. It takes the name of the container as an argument and optionally a command to execute inside the container. If no command is specified, it creates a new shell inside the container1. For example, to list all the files in the home directory of a container named myContainer, one can use:

lxc-attach -n myContainer – ls -lh /home

References:

1: Executing a command inside a running LXC - Unix & Linux Stack Exchange

Libvirt supports creating and managing various types of virtual networks that can be used to connect virtual machines to each other or to the external network. One of the common types of virtual networks is the NAT-based network, which uses network address translation (NAT) to allow virtual machines to access the outside world through the host’s network interface. By default, libvirt creates a NAT-based network called ‘default’ when it is installed and started. This network appears as a standard Linux bridge device on the host system, named virbr0. The bridge device has an IP address of 192.168.122.1/24 and acts as a gateway and a DHCP server for the virtual machines connected to it. The bridge device also has iptables rules to forward and masquerade the traffic from and to the virtual machines. The virtual machines connected to the ‘default’ network have their own IP addresses in the 192.168.122.0/24 range and their own MAC addresses generated by libvirt. The virtual machines can communicate with each other, with the host, and with the external network through the bridge device and the NAT mechanism12.

The other statements in the question are false regarding networking with libvirt. Libvirt’s network functionality is not limited to connecting virtual machines to a physical network interface of the host system. Libvirt can also create isolated networks that do not have any connection to the outside world, or routed networks that use static routes to connect virtual machines to the external network without NAT3. Libvirt does not assign the same MAC address to all virtual machines and isolate their network interfaces at the link layer. Libvirt assigns a unique MAC address to each virtual machine and allows them to communicate with each other at the network layer4. Libvirt does not require a dedicated network interface that may not be used by the host system. Libvirt can share the host’s network interface with the virtual machines using NAT or bridging, or it can pass a physical network interface to a virtual machine exclusively using PCI passthrough5. Libvirt does not support exactly one virtual network and connect all virtual machines to it. Libvirt supports creating and managing multiple virtual networks with different names and configurations, and connecting virtual machines to different networks according to their needs6. References:

libvirt: Virtual Networking

libvirt: NAT forwarding (aka “virtual networks”)

libvirt: Routed network

libvirt: MAC address

libvirt: PCI passthrough of host network devices

[libvirt: Network XML format]