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

 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 command lxc-checkpoint is used to checkpoint and restore containers. Checkpointing a container means saving the state of the container, including its memory, processes, file descriptors, and network connections, to a file or a directory. Restoring a container means resuming the container from the saved state, as if it was never stopped. Checkpointing and restoring containers can be useful for various purposes, such as live migration, backup, debugging, or snapshotting. The command lxc-checkpoint has the following syntax:

lxc-checkpoint {-n name} {-D path} [-r] [-s] [-v] [-d] [-F]

The options are:

• -n name: Specify the name of the container to checkpoint or restore.
• -D path: Specify the path to the file or directory where the checkpoint data is dumped or restored.
• -r, --restore: Restore the checkpoint for the container, instead of dumping it. This option is incompatible with -s.
• -s, --stop: Optionally stop the container after dumping. This option is incompatible with -r.
• -v, --verbose: Enable verbose criu logging. Only available when providing -r.
• -d, --daemon: Restore the container in the background (this is the default). Only available when providing -r.
• -F, --foreground: Restore the container in the foreground. Only available when providing -r.

The command lxc-checkpoint uses the CRIU (Checkpoint/Restore In Userspace) tool to perform the checkpoint and restore operations. CRIU is a software that can freeze a running application (or part of it) and checkpoint it to a hard drive as a collection of files. It can then use the files to restore and run the application from the point it was frozen at1.

The other statements about the command lxc-checkpoint are not correct. It does not create a clone or an image of a container, nor does it double the memory consumptionof the container. It can work on both running and stopped containers, depending on the options provided. References:

• Linux Containers - LXC - Manpages - lxc-checkpoint.12
• lxc-checkpoint(1) - Linux manual page - man7.org3
• CRIU4

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”).