LPIC Level 3 305-300 LPI Study Notes

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

 Vagrant is a tool that allows users to create and configure lightweight, reproducible, and portable development environments. Vagrant supports multiple providers, which are the backends that Vagrant uses to create and manage the virtual machines. By default, VirtualBox is the default provider for Vagrant. VirtualBox is still the most accessible platform to use Vagrant: it is free, cross-platform, and has been supported by Vagrant for years. With VirtualBox as the default provider, it provides the lowest friction for new users to get started with Vagrant. However, users can also use other providers, such as VMware, Hyper-V, Docker, or LXC, depending on their preferences and needs. To use another provider, users must install it as a Vagrant plugin and specify it when running Vagrant commands. Users can also change the default provider by setting the VAGRANT_DEFAULT_PROVIDER environmental variable. References:

Default Provider - Providers | Vagrant | HashiCorp Developer1

Providers | Vagrant | HashiCorp Developer2

How To Set Default Vagrant Provider to Virtualbox3

 The Linux kernel module that must be loaded in order to use QEMU with hardware virtualization extensions is KVM (Kernel-based Virtual Machine). KVM is a full virtualization solution that allows a user space program (such as QEMU) to utilize the hardware virtualization features of various processors (such as Intel VT or AMD-V). KVM consists of a loadable kernel module, kvm.ko, that provides the core virtualization infrastructure and a processor specific module, kvm-intel.ko or kvm-amd.ko. KVM must be loaded into the kernel of the host system in order to use the virtualization extensions of the host system’s CPU. This enables QEMU to run multiple virtual machines with unmodified Linux or Windows images, each with private virtualized hardware. KVM is integrated with QEMU, so there is no need to load it into the kernel of each virtual machine or the first virtual machine. KVM also does not require paravirtualization, which is a technique that modifies the guest operating system to communicate directly with the hypervisor, bypassing the emulation layer. References:

Features/KVM - QEMU

Kernel-based Virtual Machine

KVM virtualization on Red Hat Enterprise Linux 8 (2023)