Basic introduction: Linux operation system has seven levels: Run Level 0 : indicates that the system is shutdown, the default mode is not set, otherwise the system is always turned off. Run Level 1 : indicates that the system is in single user working condition, have root user privileges. Run Level 2 : the system is in no network, multi-user mode run level 3 : the system is in with a network of multi-user state mode, a terminal window interface run level 4 : The system further is the level used as a reservation operation Level 5 : the state of the system is the graphical interface level, the desktop display mode run level 6 : a normal system shutdown and restart, the default mode is not set, otherwise the system is always in a state reboot
Set system-level operation mode (only hosts influential, has no effect on remote login): The first way: using the command init number of levels (0--6) to set up
a second way: by modifying the / etc / inittab file to change the operating level
Service Management Directive
View the system has a service: The first way: Setup instructions a second way: View /etc/init.d directory contents
Order management services: serve service names start / stop / restart / reload / status can control the state of the service by the latter option, the order to execute effective immediately, but after a restart on the failure
chkconfig command: This command can be set up to service the needs of different operating levels to open and close the first use: chkconfig --list can be used to view the current status of each service at all levels of
the second usage: chkconfig --list service name used to View a service level of the current status of each run
third use: chkconfig --level number of levels (0--6) service name on / off can be used to set the number of the corresponding level for a service on or off.