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The main process of Centos booting is as follows:

1. Find the system boot partition, execute the boot program, and load the kernel

2. Execute the init program

   a. /etc/rc.d/rc.sysinit # The first script executed by init

   b. /etc/rc.d/rc $RUNLEVEL # $RUNLEVEL is the default running mode, and the running level of the server is 3

   c. /etc/rc.d/rc.local #After the corresponding level of service is started, execute the file (in fact, you can also write the commands that need to be executed into the file)

   d. /sbin/mingetty # Wait for user login