In the context of iptables, the INPUT chain is responsible for processing incoming packets destined for the local system. This is where rules for packets directed at the firewall-hosted services and applications are defined, allowing or blocking them based on the rules configured in the chain.

When a Linux server fails to boot after an update, you should begin troubleshooting by checking the system logs in /var/log. Specifically, you can look at logs such as /var/log/syslog and /var/log/boot.log to identify any error messages or issues that occurred during the boot process.

The first program run by the Linux kernel when it starts is typically the init program (or its modern replacement, such as systemd). Init is responsible for initializing the system, starting services, and setting up the user environment.

To view the route taken by packets to reach a network host, you would use the traceroute command. Traceroute provides a detailed path analysis of how packets traverse the network, including the IP addresses of each hop and response times. It's a valuable tool for diagnosing network issues.

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.

The correct command to grant temporary elevated privileges in Linux is sudo, which stands for "superuser do." The sudo command allows authorized users to execute a command as the superuser or another user, providing a level of access control.