I know the system management-general Linux technology-Linux technology and application information. The following is a detailed description. I have long wanted to write a log about system management. Nothing else. One is to summarize what I have learned by the system. The two are easy for my colleagues to learn. In fact, the four words System Management contain many things, such as system user management, system software package management, device management, and kernel management. (The server part will not be written, I will try again later ). Too many, so I will write about user management in part today. It is not well written. Don't laugh at me ^_^ (the following uses centos 5.1 as an example)
For user management, write the following five parts: first write the user account
We know that linux is a multi-user and multi-task system. To put it bluntly, a host can be used by multiple people at the same time and each user can execute multiple tasks at the same time. For example, now, Michael Jacob is developing a program. At the same time, Mr. Li is chatting online and watching movie a ^ _ ^ while listening to music. In order to correctly provide services to each user, the system must be able to correctly differentiate each user, that is, each user has its own account. The system can differentiate who serves according to the user account, strong! ^_^.
However, this alone is not enough, because there are many other features besides the name of the user. An account is used to specify all files, resources, and information of a user. Common features include user groups, management permissions, and execution permissions. For example, if a user belongs to a management group, the user can change the hardware settings and view other user files, ordinary users can only view and open their own files.
When talking about user accounts, you have to mention root. As a special user in the system, Super Users (root users) have the right to change the entire system, however, to convert itself into a Super User, you must first have the root user login password, which is usually a secret that requires strict protection and is generally only available to the system administrator. To truly become a super user, you must log on to the system using an account (that is, ROOT), which is a special account reserved for the operation of the system administrator, all parts of the linux operating system have unrestricted access permissions. When you log on to the system as the root directory, an operation interface (shell) is provided for the system administrator to publish linux commands first ).
The command to log on as a Super User is as follows:
Login: root
Passwd:
#
As the root user, you can use the passwd command to modify the password required to log on to the system as the root user, or modify the passwords of other users on the system, as shown below:
[Root @ centos ~] # Passwd root
Changing password for user root.
New UNIX password:
Retype new UNIX password:
Passwd: all authentication tokens updated successfully.
[Root @ centos ~] #
Note that when you enter the password, the password will not be displayed on the screen.
If you want to log on to the root user account and become a super user, the easiest way is to log out of your normal account first, then, log on to the system as the root user. Another way is to use the su command, which can directly log on to the root user account without exiting the original user account. Press CTRL + D or enter the exit command to return the user to the initial login status. For example:
[Xu @ centos ~] $ Pwd
/Home/xu
[Xu @ centos ~] $ Su
Password:
[Root @ centos xu] # cd
[Root @ centos ~] # Pwd
/Root
[Root @ centos ~] #
If you want to know the detailed usage of su, you can refer to man su. <指新手啦> Some commands in the centos system do not exist, such as ifconfig. Input ifocnfig in the terminal, which may be like this:
[Xu @ centos ~] $ Ifconfig
Bash: ifconfig: command not found
[Xu @ centos ~] $
You do not have full root permissions. You can add the parameter-l. See this:
[Xu @ centos ~] $ Su-l
Password:
[Root @ centos ~] # Ifconfig
Eth0 Link encap: Ethernet HWaddr 00: 16: 76: 51: A5: D1
Inet6 addr: fe80: 216: 76ff: fe51: a5d1/64 Scope: Link
Up broadcast running multicast mtu: 1500 Metric: 1
RX packets: 454 errors: 0 dropped: 0 overruns: 0 frame: 0
TX packets: 360 errors: 0 dropped: 0 overruns: 0 carrier: 0
Collisions: 0 FIG: 1000
RX bytes: 146323 (142.8 KiB) TX bytes: 49296 (48.1 KiB)
Because I have never used other systems, and I don't know their su restrictions, so I won't talk about them here.
Remember that if you have logged on to the system as the root user, you can use the su command to directly log on to any user without entering the password again, a bit like this:
[Xu @ centos ~] $ Su
Password:
[Root @ centos xu] # su xu
[Xu @ centos ~] $
Okay, let's write it here today. I'm tired of typing. I'll write it again tomorrow ......
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