Since a beginner learned Unix for the first time, I will summarize the important points and output it as well as fixing it. I hope that similar beginners will get used to it with a little effort.
If you study with Unix, you will also see the word Linux. It's basically the same ** OS **. If you are a beginner here, what is "OS" in the first place? I think it's like that, so I'd like to start with that explanation.
There are various types of ** OS **, which are summarized in the table below.
|android||Use a smartphone as hardware|
|iOS||iphone as hardware|
|Windows||Use a PC as hardware|
|Mac OS||Use a PC as hardware|
|Unix||Use the server as hardware|
|Linux||Use a PC or server as hardware|
I think I've heard a few of them. One of these includes Unix and Linux. Each has its own characteristics.
This is the oldest existing OS.
OS stability is high and network function is excellent. Therefore, Unix is the overwhelming majority of operating systems for large computers and network servers.
It is an OS made from 0 with reference to Unix. It is used in many personal computers and smartphones.
Published as free software, anyone can freely develop, distribute and use it.
Many companies distribute with their own configurations and settings, and the distribution format is called ** distribution **.
Works lightly on low performance computers.
CUI, which was one of the two introductions, is an interface, and there are two types of GUI. ** GUI **: An interface that graphically represents file operations. It can be operated using a mouse, track board, touch panel, etc.
** CUI **: An interface that displays information in characters and performs all operations using the keyboard. Command By typing a command, you can operate files and start applications.
To summarize the commonalities of the two features mentioned so far
You can see that. What is the last difference? But the big thing is
It turned out that the point can be mentioned.
I explained that Unix is a CUI-based OS, but it operates in a cycle of entering commands and then entering commands again from the results displayed there. It is the kernel that performs these various processes. Users can do many things with the features managed by the kernel. But the kernel is just doing the work, not interpreting or executing it. That is the ** shell **.
It is called a shell because it exists between the user and the kernel and wraps around the kernel. What they are doing is that the command that the user operates and inputs is once received and interpreted by the shell, and the command is executed so that the kernel can understand it and request processing. And it has the role of interpreting the result and outputting it to the screen.
Unix is available to multiple users on a single computer and must be logged in first. Therefore, there is a ** user ID ** to identify a particular user. It is then assigned a login name or account name, which can also identify the user. Users are also divided into ** admin users ** and ** general users **. The ** admin user ** has maximum computer privileges and can execute all commands, access directories, manage the system, and configure settings. Therefore, it is common to set ** general users ** for each role so as not to make mistakes.
As mentioned above, there are multiple users. In addition, each user has different privileges and can use different directories. Therefore, there is a function called ** group ** to make it easier to manage on the system. Users always belong to one group, and can also belong to multiple groups.
Access rights are settings for which users can perform what operations on all files and directories.
$ ls -l :Check access rights