Principle start Linux system
RHEL startup principles
BIOS self-test -MBR- start loading the kernel init process GRUB- of -systemd
systemd initialization process
load services need to mount the file system / etc / fstab
systemd is the first process linux kernel boot, replacing the init
The advantages of systemd:
start fast, providing a snapshot of system services, the service is automatically updated in real time
pstree command to view the process first started, pid is 1
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the init systemd and compare
init0 systemctl poweroff shutdown
init1 systemctl isolate rescue.target single-user mode
init3 systemctl isolate multi-user.target multi-user mode, character-based interface
init5 systemctl isolate.graphical.target graphical interface
init6 systemctl reboot reboot the system
vim / etc / inittab run level system documentation
to see the current default run level
systemctl get-default
to set the default run
systemctl set-default
Call the character-based interface
systemctl isolate multi-user.target
call character interface and the default operating level
systemctl set-default multi-user.target
Switching the operating level
systemctl isolate multi-user.target
Set to guide the grub
vim / etc / default / grub
using the grub2-mkconfig changes to take effect
view the grub configuration file
vim /boot/grub2/grub.cfg
Covering the implementation of
grub2-mkconfig -o /boot/grub2/grub.cfg
The main command systemd is systemctl
systemctl Start service names start a service
systemctl restart the service name to restart a service
systemctl stop service name to stop a service
systemctl status service name to view a service of state
systemctl enable the service name to set up a service at startup
systemctl disable the service name set up a service boot automatically shut down
init5 switch to a graphical interface
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view atd status of the service,
systemctl Status atd
Apache installation package
yum -y install httpd
systemctl enable httpd
ststemctl disable httpd
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view the system is in service of those boot from the start of
systemctl list-unit-files --type service
to view the system resources occupied in the service of the state
systemd-cgtop