1 run level is specified
linux operating seven levels:
0: Off
1: single user (password to retrieve lost)
2: no network service multiuser state
3: state in which a multi-user network services
4: Reserved
5: GUI
6: system reboot
common level is 3 and 5, if you want to change the default operating level, can be modified / etc / inittab
switch to the specified operating level instructions: init [012356]
How to retrieve the root password?
Single-user mode, and then modify the root password. Because the single-user mode, root can log in without a password.
note! ! ! ! !
CentOs7 input vim / etc / inittab message can be seen, run level runlevels is no longer used, is replaced Targets, there are only two target: multi-user.target and graphical.target, respectively corresponding to the original levels 3 and 5.
Prompt information prompts to set target level that is run in the following manner
To view current default target, run:
systemctl get-default
To set a default target, run:
systemctl set-default TARGET.target
2 Help command
When we are not familiar with a command, you can use Linux to help provide instruction to learn how to use this directive.
- man
man command or configuration file
function: get help - Help
Help command
functions: shell built-in commands to get help information
