1.2 Linux Philosophical thought

Linux philosophy thought:
Free thinking
Purpose of a single small program composition, usually a complex system is a number of the following soft, especially when we configure the service later, so we have to do is to assemble the small program, complete complex tasks, we need to complete the manual
Everything is file, even the access to the device is a file, the following Linux directory structure will tell you what files are under each directory, and even what these access portals correspond to what files, how these files are created, and so on
Try to avoid capturing the user interface, is to try to avoid interacting with the user, a user initiated a process, in general, do not use the customer to do anything else, enter any information, such as input LS when the direct output of the results
The configuration file is saved in plain text format, so if you want to configure a service on Linux, you only need a text editor to complete all the configuration.
Strictly case-sensitive, which is different from windows
I'll never write it all.

interface and classification of human-computer Interaction:
GUI interface and CLI interface
GUI interface Human-computer interaction--double-click icon
Cli:
Command prompt, super User #, normal user $
Why did we enter the command and hit enter to execute it? What the hell is going on behind this?
The shell is a command-line interface, so after we enter the command, the shell will enter the command into the kernel to determine whether the program has execute permissions, and whether it can execute, and where to start execution
We said that every program wants to be executed, must have the execution entrance, then if a program cannot execute, the kernel will return an error
The kernel is no different, whether through the shell or the graphical interface through the shell to convert the operation to the corresponding command to the kernel, but it is different from the user

Format of the command:
The command itself, which is the path to the executable, the name of the command or script, and other doubts.
Options to fix how commands are executed
Long options and short options, short options can be combined between, long options cannot be combined
Parameters, the object of the command, the command to whom the effect, for the different commands can receive parameters, the number of receive parameters is also different

To enable user Switching "
Computers are scarce resources, and only those with credentials can use them.
Use credentials, what is the use of credentials, what the operating system user is used to do
Assuming there are no users, the computer starts directly into the operating system and can use all the resources, so the user is a way to implement the credentials
Besides, fingerprints, iris recognition technology.
Everyone's user name is root, take and how to verify the identity of the user, which requires the corresponding password, authentication through, is to use the user to identify the number of resources can be obtained
For example, everyone in a company to work, can be entered through the employee card, but certainly the authority is not the same, timely through the user to distinguish different permissions

Virtual terminal for Linux:
Multiple virtual login interface, different computer keyboard mapping way, but can use the keyboard to achieve different login interface between the switch, such as CTRL+ALT+F2, enter the interface 2
Is the simulation is a multi-user environment, equivalent to virtual out a few different monitors, we call the terminal
Generally there are 6 terminals can be switched, this is the default, but we can define ourselves, is CTRL+ALT+F1---F6
StartX &--can start the graphical interface or use CTRL+ALT+F7, but the first time you must use the command
The flexibility of Linux is the ability to start multiple graphical interfaces

Analog Terminal:
A terminal that is opened by right-clicking on the graphical interface

Types of graphical interfaces for Linux:
GNOME:C Development
kde:c++ Development
Xface:s is a lightweight desktop operating system for embedded
It is said that Ubuntu in addition to a Linux mobile phone operating system, the interface is very beautiful, the company has been developing Ubuntu mobile phone
There are different versions of Ubuntu, the GNOME version, the KDE version, the Xface version, the desktop is not the same, on the Redhat, two desktops are provided, but we usually only installed GNOME, there are two different styles of desktop style completely different
Window GUI called Window,linux's desktop called X-window,x refers to the Linux graphics display protocol, windows before 2008 desktop is built in the kernel, must be installed, do not use the desktop can not be installed, Linux desktop is just a software , and the Linux x-windows is the CS architecture, that is, the current host is installed system, another host is a monitor, it is also completely possible to display and the desktop can be separated to show that the end is the server, the request shows that the end is the client

Types of Linux CLI interfaces:
The same is the program, there are many types
The default is bash, and the second csh,zsh,ksh,tcsh, we'll just have one.
Bash is the most widely used and most powerful shell, which is the shell that the shell uses by default, and the default shell is sh, which is actually a link to bash.
SH is the original shell and a research and development lab at Bell Labs.
Anyway, the shell is a user interface that lets the user enter commands and retrieve the result of the command run to the screen of the current shell, or the human-computer interface.
Any shell-related programs are closed when the shell is closed.

The two most identical laboratories in the world:
Xerox's Pack labs, like Ethernet, mouse, and graphical user interface are all pack labs

To switch users:
SU---switch user
Return the original User---exit
-L: Becomes full toggle, no-l is half-switched

To modify a user password:
passwd--Modify the password of the current user, connect two times
For Superuser, you can modify the user's password arbitrarily, but generally follow the rules of password complexity for ordinary users.

Password complexity rules;
Complex enough, numbers, lowercase letters, uppercase letters, special characters, four to three,
Long enough, generally more than 7 bits, length, for an email address to do password, if brute force hack (there is a dictionary), no three years five years is not cracked out of
Using random strings
Regular replacement, others spent half a year to crack out, who know you even a month before the change
Cycle time to hit, it is best not to use the most recent password, in the password complexity rules, generally we will stipulate that the last 24 hours of use of the password
We will learn how to generate random strings to do passwords, then encrypt them with a password to save them, followed by the advantages and disadvantages of each encryption method
A password is a credential when a user obtains a resource
So now the way to encrypt more, more secure, brush fingerprints, brush the iris, these facts are to enhance the authentication complexity of the
Online banking is also the case, know the password is not enough, when the transfer will also send a verification code on the phone, and through the U-Shield, there is a unique certificate

1.2 Linux Philosophical thought