(shusheng007) Do you know Linux file permissions and chmod command?

From: shusheng007

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Overview

The first time I came into contact with Linux was when I followed the online tutorial to install Tomcat on the server. I always heard the sudo command. I didn’t know what it was, so I just copied and pasted it, and finally the installation was successful. The sad thing is that I logged in with the root account, and I also used sudo?

Knowledge is such a common Linux command. In fact, a problem may seem like a piece of rubbish to veterans, but it is a huge mountain for beginners. Here I will briefly talk about my understanding of this command, which is all regarded as study notes. , in fact, I hope it can help other colleagues in need.

SUDO usage background

The full name of Sudo is: superuserdo. As the name suggests: do what a super user can do! Therefore, the most commonly used function of Sudo is to increase the execution permission of a named name.

As we mentioned in the article Understanding Linux file permissions and chmod commands in seconds, Linux manages permissions by users and groups. If the account you use does not have enough permissions, you will not be able to do some actions, such as restarting the server ( reboot command), what should I do?

Some friends want to fight, isn't the root account good? Do you think that every server is bought by your family? linux restart service command, anyone can use root? Although the main purpose of this command is to solve the problems that exist during the use of root. Root privileges are too great, and leakage or misoperation will lead to huge risks, so sudo was born! Therefore, even if you have root privileges, using this command can avoid irreparable losses or trouble caused by misoperation.

SUDO function

sudo is a Linux system management command. It is a tool that allows system administrators to let ordinary users execute some or all root commands, such as halt, reboot, su, etc. In other words, this command allows non-root users to run commands that only root has permission to execute.

SUDO Principle

Can every newly created user use sudo to increase the command permissions? If not, what user can use this command?

In order for a user to have the ability to use sudo, the root user needs to register his name, specific commands that can be executed, and the identity of which user or user group to execute as, etc. in the /etc/sudoers file. That is, the authorization of the user must be completed (the user is called "sudoer" at this time).

When a normal user executes special permissions, add sudo before the command. At this time, the system will ask you to enter a password to confirm that you are operating in front of the terminal. After confirmation, the system will process the command as a super user. permission to run.

Within a certain period of time, the password will no longer be asked when executing the sudo command again Linux restart service command . After this period of time (usually 5 minutes), you need to enter the password again.

Specific use

It is assumed that the company's services use the Ubuntu18.04 operating system

When the intern girl Niu Cuihua reports for internship at "Perry Tomato Technology" company, the director Wang Ergou needs to create an account for her that can use the sudo command. What should she do?

Step one: Ergou first logs in to the root account and uses the following command to create an account: cuiHuaNiu.

addusercuiHuaNiu

During the creation process, you need to specify the password of the cuiHuaNiu account, as well as other personal information, such as phone number, etc. Ergou can also take the opportunity to get the girl's phone number.

Step 2: Grant cuiHuaNiu administrator rights, that is, register it in the /etc/sudoers file

By default, there is a sudo group on Ubuntu 18.04. Users belonging to this group can use sudo commands, so Ergou only needs to add cuiHuaNiu to the sudo group.

usermod-aGsudocuiHuaNiu

The -a parameter indicates attachment, and is only used with the -G parameter to reduce the user to the group.

Step 3: Niu Cuihua can use cuiHuaNiu to log in to the server, and then use sudo to execute commands that the administrator can execute. In fact, if Cuihua has root permissions, you can also use sudo-i to switch the user identity to root.

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Advantage summary

You can see the Linux server setup here, which means you accidentally learned a common Linux command. Are you angry? It is recommended to like and collect, be a real IT person, willing to share, dare to contribute, help each other...

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