This is the 24th day of my participation in the wenwen Challenge
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Check the system memory usage
The log view
Log files are files that contain information about the system, including the kernel, services, and applications running on the system. Different log files record different information. Most log files are located in the /var/log directory. Some programs, such as Samba, have a separate directory for log files in /var/log. Logs can be scrolled
Most log files are in plain text format and can be viewed using any text editor such as VI. Most log files require a privilege to be viewed.
System initialization process
The BIOS initializes
Mainly responsible for computer hardware detection, determine the boot sequence, load and execute boot programs from bootable devices (such as the main disk boot partition MBR), determine where to boot and start the operating system, after successful boot, the kernel is responsible for
GRUB loading
A program user who installs the Boot Loader into the master Boot Record (MBR) can initiate operating system selection, pass specific instructions to the kernel at Boot time, or determine some system parameters before the kernel boots. Support command interactive tools, provide a very convenient boot program repair function, and support the encryption of the boot menu protection
Kernel initialization
After a user selects an appropriate boot option from the GRUB boot menu, the OS starts to load the kernel. Kernel initialization:
- Hardware inspection
- Initialization of the device driver
- Mount the root file system in read-only mode
- Start the first application process init
The first initial process init starts
When the kernel is started, the kernel part of the boot process is completed by starting the user-level program init. Init is always the first process (PID=1). The init process acts as the ultimate parent process, and children who lose their parent process use init as their parent process.
Determine the system operating level
Read the /etc/inittab configuration file, which is a system initialization script used to determine the runtime level at which the system starts and define general system functions.
Run the system initialization script
/etc/rc.d/rc.sysinit is the system initialization script that implements most of the system functions
Runs the script in the specified level directory
Each particular runlevel has a directory associated with it. There are seven runboundaries (/etc/rc.d/rc[x].d), and each runlevel directory contains some executable scripts.
Run user-defined scripts
You can customize some scripts for system startup and modify the contents in /etc/rc.d/rc.local to add functions required by you.