Detailed explanation of Linux switch user su instruction misunderstanding

1. Background

For security reasons, general accounts are generally recommended for general operations in a Linux environment

This is because the root account permissions are too large, often due to careless misoperation caused by system errors, serious will also cause the system to crash and collapse.

It is recommended that you switch to the root account only when you need to do so.

Su is the operating instruction of the switching user in the Linux environment

2.su Instruction

Many friends use this instruction often in the following form:

Example: Switch from general account moonlit to root account

$ su

So what's wrong with doing this?

We'll look at the comparison of the data before and after the account switching.

[[Email protected] ~] $

Execute the following statements before switching to see the variables in your environment that contain moonlit:

$ env | grep ' moonlit '

The screen appears as follows:

User=moonlit
Mail=/var/spool/mail/moonlit
path=/usr/java/jdk1.7.0_60/bin:/usr/lib64/qt-3.3/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/ Sbin:/home/moonlit/bin
Pwd=/home/moonlit
Home=/home/moonlit
Logname=moonlit

To perform a switchover:

$ su

Password:

After entering the password, the screen is converted to:

[[Email protected] ~] #

Enter #pwd to view the current path

/home/moonlit

Hey, how is it still in the home directory of the moonlit account?

Re-enter # env | grep ' moonlit '

Screen output:

User=moonlit
path=/usr/java/jdk1.7.0_60/bin:/usr/lib64/qt-3.3/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/ Sbin:/home/moonlit/bin
Mail=/var/spool/mail/moonlit
Pwd=/home/moonlit
Logname=moonlit

Did you see that? Environment Wood has changed.

Because there is no change to the root environment, it can cause many root commands to be wrong or invalid.

To fully convert the user to root, you can use the following command:

[email protected] ~]$ su -

Type the root password and change to [[email protected] ~]#

#pwd一下:

/root

Again # env | grep ' moonlit ' a bit:

No God, no horse.

# env a bit:

This time the screen will be all the variables displayed, more, not listed, you can see the current home directory, PATH, mail and so on have all been changed to the root of the variable.

Finally, you can release #exit to exit the current root user and return to moonlit.

3. Summary

In fact no-when the system is in accordance with the Non-login shell way to switch users,

Plus-When the system is switched according to the login shell.

Detailed explanation of Linux switch user su instruction misunderstanding