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

The command that deletes all volumes which are not associated with a container is docker volume prune. This command removes all unused local volumes, which are those that are not referenced by any containers. By default, it only removes anonymous volumes, which are those that are not given a specific name when they are created. To remove both unused anonymous and named volumes, the --all or -a flag can be added to the command. The command will prompt for confirmation before deleting the volumes, unless the --force or -f flag is used to bypass the prompt. The command will also show the total reclaimed space after deleting the volumes12.

The other commands listed in the question are not valid or do not have the same functionality as docker volume prune. They are either made up, misspelled, or have a different purpose. These commands are:

docker volume cleanup: This command does not exist in Docker. There is no cleanup subcommand for docker volume.

docker volume orphan -d: This command does not exist in Docker. There is no orphan subcommand for docker volume, and the -d flag is not a valid option for any docker volume command.

docker volume vacuum: This command does not exist in Docker. There is no vacuum subcommand for docker volume.

docker volume garbage-collect: This command does not exist in Docker. There is no garbage-collect subcommand for docker volume.

References:

docker volume prune | Docker Docs

How to Remove all Docker Volumes - YallaLabs.

LXC (Linux Containers) is a lightweight virtualization technology that allows multiple isolated Linux systems (containers) to run on the same host. LXC uses Linux kernel features such as namespaces, cgroups, and AppArmor to create and manage containers. Each container has its own file system, network interfaces, process tree, and resource limits. However, containers share the same kernel and hardware with the host, which makes them more efficient and faster than full virtualization.

By default, an LXC container has a minimal set of devices that are needed for its operation. These devices are created by the LXC library when the container is started, and are removed when the container is stopped. The default devices are:

/dev/log: This is a Unix domain socket that connects to the syslog daemon on the host. It allows the container to send log messages to the host’s system log1.

/dev/console: This is a character device that provides access to the container’s console. It is usually connected to the host’s terminal or a file. It allows the container to interact with the user or the host’s init system12.

/dev/urandom: This is a character device that provides an unlimited source of pseudo-random numbers. It is used by various applications and libraries that need randomness, such as cryptography, UUID generation, and hashing13.

The other devices listed in the question do not exist by default in an LXC container. They are either not needed, not allowed, or not supported by the container’s namespace or cgroup configuration. These devices are:

/dev/kmem: This is a character device that provides access to the kernel’s virtual memory. It is not needed by the container, as it can access its own memory through the /proc filesystem. It isalso not allowed by the container, as it would expose the host’s kernel memory and compromise its security4.

/dev/root: This is a symbolic link that points to the root device of the system. It is not supported by the container, as it does not have a separate root device from the host. The container’s root file system is mounted from a directory, an image file, or a loop device on the host5.

References:

Linux Containers - LXC - Manpages - lxc.container.conf.5

Linux Containers - LXC - Getting started

Random number generation - Wikipedia

/dev/kmem - Wikipedia

Linux Containers - LXC - Manpages - lxc.container.conf.5

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