kexec_load is a system call in Linux that loads a new kernel image into memory for execution, effectively allowing a Linux system to perform a fast reboot without going through the full hardware initialization process. This system call is particularly useful in situations where a system crash occurs or when administrators need to load a different kernel without rebooting the entire system.
Understanding the nuances of the kexec/kdump interfaces in Red Hat Enterprise Linux (RHEL) is crucial for users aiming to achieve optimal performance and reliability. While the default choice is kexec_file_load, the availability of kexec_load provides flexibility to users, enabling them to customize their systems based on their specific requirements. Red Hat maintains its commitment to supporting both interfaces, guaranteeing a seamless experience for users across diverse use cases.
Here’s a breakdown of how `kexec_load` works:
1. Loading a New Kernel Image: When invoked, `kexec_load` loads a new kernel image into memory. This kernel image can be either a different version of the currently running kernel or a completely different kernel altogether.
2. Specifying Kernel Parameters: Along with the kernel image, `kexec_load` allows administrators to specify parameters for the new kernel. These parameters can include boot options, command-line arguments, and any other configuration settings required by the kernel.
3. Avoiding Hardware Initialization: Unlike a traditional system reboot, where the hardware goes through a full initialization process, `kexec_load` bypasses hardware initialization. This results in a faster reboot process since the system does not need to reinitialize hardware components such as the CPU, memory, and peripherals.
4. Preserving System State: kexec_load preserves certain aspects of the system state, such as the contents of memory and the CPU state, before loading the new kernel image. This allows for a seamless transition between the old and new kernels, minimizing downtime and disruption to running processes.
5. Usage Scenarios: kexec_load is commonly used in scenarios where a system crash occurs and administrators need to quickly reboot the system using a known good kernel image. It can also be used for kernel testing, debugging, and performing system upgrades without the need for a full system reboot.
As of Red Hat Enterprise Linux (RHEL) 8, the default interface for loading kexec/kdump kernels is kexec_file_load. This significant change represents a strategic decision aimed at harnessing the kernel’s capabilities in this critical process.Even though there has been a transition to using the kexec_file_load interface as the default method for loading kexec/kdump kernels in Red Hat Enterprise Linux (RHEL) 8, it’s important to note that the kexec_load interface remains available. This means that users still have the flexibility to revert to using kexec_load if they have specific requirements or preferences that necessitate its use.
Overall, `kexec_load` provides a valuable mechanism for efficiently loading and executing kernel images in Linux systems, offering administrators greater flexibility and control over system reboots and kernel changes.