Here are some of the key points from the certification objectives in Chapter 8.
❑ | The kernel lies at the heart of the operating system. |
❑ | Modular kernels, with separate device modules, are more efficient than monolithic kernels, where device drivers are integrated into the kernel. |
❑ | If you're going to update your kernel, you should keep a copy of your current working kernel. |
❑ | Linux kernels and related files are stored in the /boot directory. |
❑ | The /proc directory provides a window to what Linux sees in your computer. |
❑ | The lsmod command lists currently loaded modules; important related commands are insmod, rmmod, and modprobe. |
❑ | Basic RHEL modules can be loaded from the kernel-devel RPM. |
❑ | Kernel version numbers are organized in major.minor.patch format. Red Hat adds a build number to the Linux kernels that it builds from source code. |
❑ | It's fairly easy to install a Red Hat kernel from RPM, as long as you remember to install and not upgrade. This allows you to return to the current working kernel if you have a problem. |
❑ | Sometimes all you need is a kernel patch, which supports upgrades of one patch version number. Unfortunately, patches are not always the best option for Red Hat built kernels. |
❑ | When you install a Red Hat kernel from RPM, the process should automatically update your GRUB boot loader. |
❑ | Kernel sources can be loaded from the kernel source RPM or from a Linux kernel tarball downloaded from a site such as ftp.kernel.org. |
❑ | Installing the Red Hat kernel source RPM requires the rpmbuild command. |
❑ | Once installed, the kernel source tree is available through /usr/src/redhat/BUILD directory. |
❑ | To optimize the Linux kernel, it is a best practice to compile kernels with only needed elements and configure modules for most hardware. |
❑ | Your current kernel configuration is stored in the config-`uname -r` file in the /boot directory. |
❑ | You can modify kernel settings from the kernel source code directory with tools that you can open with one of the following commands: make config, make menuconfig, make xconfig, or make gconfig. |
❑ | Once you've made the proper backups and boot disks and set the EXTRAVERSION variable in your Makefile, you're ready to customize your kernel. |
❑ | Once you've settled on and saved your changes, run the make rpm command. It should compile your new kernel and create an RPM in the /usr/src/redhat/RPMS directory, which you can use to install your custom kernel. |
❑ | Red Hat supports several levels of software RAID, including RAID 0, RAID 1, RAID 5, and RAID 6. |
❑ | To make software RAID work, you need to designate the partition specifically as such in fdisk or parted. |
❑ | RAID arrays as configured are shown in /proc/mdstat. |
❑ | RAID arrays can be created and modified with the mdadm command. |
❑ | LVM is based on physical volumes, logical volumes, and volume groups. |
❑ | You can create and add LVM systems with a wide variety of commands starting with pv*, lv*, and vg*. |
❑ | The GUI LVM tool is an alternative for those who don't remember all of the commands required to manage logical volumes. |