Linux Introductory Learning (ii)

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Key	function
Ctrl+d	Keyboard input end or exit terminal
Ctrl+s	Pause the current program, pause and press any key to resume running
Ctrl+z	Put the current program in the background to run, revert to the foreground commandfg
Ctrl+a	Move the cursor to the input wardrobe equivalent to the Home key
Ctrl+e	Moves the cursor to the end of the input line, equivalent to the End key
Ctrl+k	Remove from cursor position to end of line
Alt+Backspace	Delete a word forward
Shift+PgUp	Scroll the terminal display up
Shift+PgDn	Scroll down the terminal display

2) Learn to use historical input commands

Very simple, you can use the keyboard in the direction of the key ↑ to restore the command you have entered previously, you try to know.

1.touch XXX: Create a new XXX file

2.ls *. suffix: Indicates that all files with this suffix are found

3.touch Xx_{1..3}_liunx.txt: Represents new three love_x_linux.txt files

Shell Common wildcard characters:

character	meaning
*	Match 0 or more characters
?	Match any one character
[list]	Match any single character in the list
[!list]	Matches a character other than any single character in the list
[c1-c2]	Match any single word in c1-c2 such as: [0-9] [A-z]
{string1,string2,...}	Match string1 or string2 (or more) one string
{c1..c2}	Match all characters in c1-c2 such as {1..10}

View users: Who am I

The first column of the output indicates the user name of the user who opened the current pseudo-terminal (to see the user name of the currently logged-on user, remove the space and use it directly whoami )

whocommand other common parameters

Parameters	Description
-a	Print all that you can print
-d	Print the Dead process
-m	Same am i ,mom likes
-q	Print the current number of logged-in users and user names
-u	Print current logged in user login information
-r	Print Run level

In a Linux system, the root account has the supremacy of the entire system, such as new/added users.

sudo adduser xxx: new XXX user

Usually here you need to follow the prompts to enter the Shiyanlou password (Linux password input is not to show anything), Shiyanlou user password at the top of the experimental document on the left. Then is to give the Lilei user to set the password, some contents of the following option you can choose direct return to use the default value:

Ls/home: Attribute the created user to home

su-1 XXX: Switch to XXX user

This command not only adds the user to the system, but also creates the home directory for the new user by default:

$ groups shiyanlou

Where the colon is preceded by the user, followed by the user group that the user belongs to. Here you can see that the Shiyanlou user belongs to the Shiyanlou user group, and each time a new user does not specify a user group, the default is to automatically create a user group that is the same as the user name (almost equivalent to the parent's meaning, or mister)

Method Two: View /etc/groupFile

$ cat /etc/group | sort

This cat command is used to read the contents of the specified file and print it to the terminal output, which will be used in detail later. | sortindicates that the text to be read is sorted in a dictionary and then output, and then you will see the following heap of output, you can see the Shiyanlou user group information at the bottom:

No, it's okay, you can use the command to filter out some of the results you don't want to see:

$ cat /etc/group | grep -E "shiyanlou"

etc/groupFile Format description

The content of/etc/group includes the user group, user group password, GID, and the user that the user group contains, one record per user group. The format is as follows:

Group_name:password:GID:user_list

You see the password field above as a x not that the password is it, but that the password is not visible.

Add other users to the sudo user group

By default, the newly created user is not rooted or the Sudo user group can be added to the sudo user group to gain root privileges:

$ su -l lilei$ sudo ls

Will prompt Lilei not in the sudoers file, meaning that Lilei is not in the Sudo user group, as for the sudoers file (/etc/sudoers) You better not move it now, careless operation will lead to more troublesome consequences.

Use usermod the command to add a user group to the user, and you must have root permission to use the command, you can either use the root user to add a user group to another user, or use the sudo command to get permissions for other users who are already in the sudo user group to execute the command.

Here I use the Shiyanlou user to execute the sudo command to add Lilei to the sudo user group so that it can also use the sudo command to get root privileges:

# 此处需要输入shiyanlou用户密码，可以点击右侧工具栏中的“SSH直连”查看$ groups lilei$ sudo usermod -G sudo lilei$ groups lilei

Then you switch back to the Lilei user and you can now use sudo to get root privileges.

2.4 Deleting a user

Deleting a user is a simple matter:

$ sudo deluser lilei --remove-home

Third, Linux file permissions 3.1 view file permissions

We have used the command many times before, ls as you can see, we use it to list and display the files in the current directory, of course, without any parameters, it will do more than that, and now we need to use it to view the file permissions.

To list files in a longer format:

-l

You may not know the last item except the file name, so what does it mean?

Perhaps you still do not understand, such as the first file type and permissions that a bunch of things exactly what to refer to, what the link is, what is the last modification time, the following one by one ways:

• File type

About the file type, here's one thing you must always keep in mind that Linux is all files, because this is the device files ( /dev directory has a variety of device files, mostly with specific hardware equipment related) This said. socket: Network sockets, what is the specific, interested users can learn or look forward to the experiment building follow-up related courses. pipepipeline, this thing is very important, we will discuss later, here you first know that there is the existence of it. 软链接文件: The link file is divided into two kinds, the other is of course "hard link" (hard links are not commonly used, the specific content is not the focus of the course discussion, and soft link is equivalent to the shortcut on Windows, you remember this is enough).

• File permissions

Read permission, indicating that you can use cat <file name> such commands to read the contents of a file, write permission, that you can edit and modify a file;

Execute permissions, usually referred to as binaries or script files that can be run, as files that are suffixes on Windows exe , but Linux does not differentiate file types by file suffix names. One thing you should be aware of is that a directory has both read and Execute permissions to open and view internal files, and a directory with write permission to allow other files to be created, because the catalog file actually holds information such as a list of files in that directory.

Owner permissions, which you should understand, as to the user group permissions, refers to all other users in your user group to the file permissions, for example, you have a pobman, then this user group permissions determine whether your siblings have the authority to use it to destroy it and take possession of it.

• Number of links

The number of file names linked to the Inode node where the file is located (for the concept of Linux file system related concepts, not in the scope of this course, interested users can understand themselves).

• File size

With the Inode node size as the size of the file, you can give LS plus -lh parameters to see the size of the file more visually.

Understanding some of the concepts of file permissions, let's add ls some other common uses of commands:

• Displays . all files except (current directory) and .. (top level directory), including hidden files ( . files that start with Linux are hidden).

$ ls -A

Of course, you can use both -A and -l parameters:

$ ls -Al

To view the full properties of a directory instead of displaying the file attributes in the directory:

<目录名>

• Show all file sizes and present them in a way that ordinary humans can understand:

$ ls -AsSh

Where small S is the size of the display file, big S is sorted by file size, and if you need to know how to sort by other means, use the "man" command to query.

3.2 Change file Owner

Assuming that the Lilei user is currently logged in, create a new file named "Iphone6":

$ touch iphone6

The visible file owner is Lilei:

Now, to change back to the Shiyanlou user identity, change the file owner to Shiyanlou using the following command:

$ cd /home/lilei$ ls iphone6$ sudo chown shiyanlou iphone6

Now check to see that the file owner was successfully modified to Shiyanlou:

3.3 Modifying file permissions

If you have a file that you do not want to be read, written, or executed by another user, then you need to modify the permissions of the file, there are two ways:

• mode 1:2 binary digit representation

Three sets of permissions for each file (owner, owning user group, other user, remember this order is certain) corresponds to a "rwx", that is, a "7", so if I want to change the file "Iphone6" permission to only I can use it then:

To demonstrate, I'll add some content to the file:

echo "echo \"hello shiyanlou\"" > iphone6

Then modify the permissions:

chmod 700 iphone6

Now, other users can't read this "iphone6" file anymore:

• Mode two: Add and subtract assignment operation

To accomplish the same effect as above, you can:

chmod go-rw iphone6

g, as o well as u the group, others, and user respectively, + and respectively, to - add and remove the corresponding permissions.

Four, more adduserAnd useraddWhat is the difference?

A: Useradd only create users, created by using passwd Lilei to set the new user's password. AddUser will create a user, create a directory, create a password (prompting you to set up), do this series of operations. In fact, Useradd, userdel such operations more like a command, after the execution of the return. And adduser more like a program, you need to enter, determine a series of operations.

Linux also has some content about hidden permissions and special permissions, and users who want to fully understand the content of Linux Rights Management can learn in other ways.

V. Homework

Add a user loutest , use sudo Create file /opt/forloutest , set to user loutest can read and write. And the operation process is written into the experimental report.

Linux Introductory Learning (ii)