The default field separator for operations like splitting strings is determined by the IFS (Internal Field Separator) built-in variable. The IFS variable defines how the shell separates words when it parses strings, making it a crucial component for tasks like parsing CSV files or text processing in scripts.

In a shell script, you would use the $_ special variable to refer to the last argument passed. This variable holds the last argument to the last command that was executed.

In a Debian-based system, such as Ubuntu, you would likely use the 'apt-get' command to install packages. The 'apt-get' command is used for package management and is specifically designed for Debian-based distributions.

The sudo command reads configurations from /etc/sudoers to determine user privileges. This file contains information about which users can run commands with administrative privileges and under what conditions. Understanding and configuring the sudoers file is essential for managing access control in Linux.

In Linux, the syslogd daemon is responsible for logging system messages. It collects and manages log messages generated by various system components and services. klogd is used for kernel log messages, systemd is an init system, and auditd is responsible for auditing.

The correct command to load kernel modules manually is insmod. This command allows you to insert a kernel module into the running kernel. It's used when you want to load a specific module into the kernel, and it doesn't handle module dependencies automatically.

The tool commonly used to manage btrfs file systems is btrfs-progs. These utilities provide various commands for managing and maintaining btrfs file systems, including creating, mounting, and checking file systems.

The primary use of the iptables -L command is to view the current rules in the iptables firewall. It shows a list of firewall rules and their details, allowing you to inspect how traffic is being filtered or forwarded on a Linux system.

Containers enable OS-level virtualization, allowing multiple isolated user-space instances to run on the same kernel. They share the host OS's kernel but have separate user spaces, making them lightweight and efficient. Docker and Kubernetes are popular container technologies.

To temporarily change SELinux mode and allow everything while logging violations, you would use the "Permissive" mode. In this mode, SELinux will log policy violations but won't enforce them, which helps troubleshoot and analyze any issues without blocking the application.