1System startup and the Linux kernel

• 1.1The Boot Process and GRUB

  Go deep on the firmware layer from power-on to kernel handoff: the difference between BIOS and UEFI, the disk-layout contrast between MBR and the ESP (EFI System Partition), managing boot entries with efibootmgr, generating and installing GRUB2 config (grub-mkconfig/grub2-mkconfig, grub-install/grub2-install), and the role of initrd/initramfs.

• 1.2Customizing System Startup

  Go deeper on operating systemd services: the three-layer config hierarchy (/usr/lib/systemd/, /etc/systemd/, /run/systemd/), unit operations with systemctl (status, list-units, start, stop, enable, disable, mask, unmask), diffing config layers with systemd-delta, and when to use rescue vs emergency mode.

• 1.3Components of the Linux Kernel

  Learn the structure of the kernel image itself and its source tree: the compressed executable image bzImage, the xz data compression used inside it, the kernel source tree at /usr/src/linux/, and the accompanying documentation at /usr/src/linux/Documentation/.

• 1.4Compiling the Linux Kernel

  Learn the full workflow of building a kernel from source: the .config file and kernel Makefile, configuration make targets (config, xconfig, menuconfig, gconfig, oldconfig) versus build targets (all, bzImage, modules, modules_install), the mrproper cleanup target, packaging targets (rpm-pkg, binrpm-pkg, deb-pkg), the module install location /lib/modules/<kver>/, and how it connects to depmod, DKMS, and Dracut (mkinitrd/mkinitramfs).

• 1.5Managing and Troubleshooting the Running Kernel

  Learn module management and failure analysis on a running kernel: module operations (depmod, modinfo, modprobe, insmod, lsmod, rmmod) and configuration at /etc/modprobe.d/, version checks with uname, tuning kernel parameters through procfs (/proc, /proc/sys/kernel/) and sysctl (/etc/sysctl.conf, /etc/sysctl.d/), sysfs (/sys), hardware inspection (dmesg, lspci, lsdev, lsusb, journalctl), udev rules and udevadm monitor, and crash dumps via kdump/kexec.