| Red Hat Certified System Administration 8 |
Chapter 16: Basic Kernel ManagementSommaire
Understanding the Role of the Linux KernelThe Linux kernel is the heart of the Linux operating system. It takes care of many things, including hardware management. It is the layer between the user who works with Linux from a shell environment and the hardware that is available in the computer on which the user is working. The kernel manages the I/O instructions it receives from the software and translates them into the processing instructions that are executed by the central processing unit and other hardware in the computer. The kernel also takes care of handling essential operating system tasks. One example of such a task is the scheduler that makes sure any processes that are started on the operating system are handled by the CPU. Understanding the Use of Kernel Threads and DriversThe operating system tasks that are performed by the kernel are implemented by different kernel threads. Kernel threads are easily recognized with a command like [root@lab ~]# ps aux. The kernel thread names are listed between square brackets Another important task of the Linux kernel is hardware initialization. To make sure that this hardware can be used, the Linux kernel uses drivers. Every piece of hardware contains specific features, and to use these features, a driver must be loaded. The Linux kernel is modular, and drivers are loaded as kernel modules, which you read about more later in this chapter. In some cases, the availability of drivers is an issue because hardware manufacturers are not always willing to provide open source drivers that can be integrated well with the Linux kernel. That can result in a driver that does not provide all the functionality that is provided by the hardware. If a manufacturer is not willing to provide open source drivers, an alternative is to work with closed source drivers. Although these make it possible to use the hardware in Linux, the solution is not ideal. Because a driver performs privileged instructions within the kernel space, a badly functioning driver may crash the entire kernel. If this happens with an open source driver, the Linux kernel community can help debug the problem and make sure that the issue is fixed. If it happens with a closed source driver, the Linux kernel community cannot do anything. But, a proprietary driver may provide access to features that are not provided by its open source equivalent.Working with Kernel ModulesUpgrading the Linux KernelUPGRADING THE LINUX KERNELFrom time to time, you need to upgrade the Linux kernel. When you upgrade the Linux kernel, a new version of the kernel is installed and used as the default kernel. The old version of the kernel file will still be available, though. This ensures that your computer can still boot if in the new kernel nonsupported functionality is included. To install a new version of the kernel, you can use the command yum upgrade kernel. The yum install kernel command also works. Both commands install the new kernel beside the old kernel. The kernel files for the last four kernels that you have installed on your server will be kept in the /boot directory. The GRUB 2 boot loader automatically picks up all kernels that it finds in this directory. This allows you to select an older kernel version while booting, which is useful if the newly installed kernel doesn’t boot correctly. |
