Rhcsa Notes 6

1.linux Type of user in

Divided into three categories ：

The super user —— The user is called root, It has all permissions , Only system maintenance ( for example ： Establish users, etc ) Or other necessary

Only use super user login , To avoid security problems in the system .

System users （ Dummy user ）—— yes Linux Users necessary for the normal operation of the system . Mainly to meet the corresponding system process

The document is established at the request of the owner , for example ：bin、daemon、adm、lp Waiting for users . System users cannot log in .

Ordinary users —— To enable users to use Linux System resources , Most of our users fall into this category .

linux Type of user group in

There are two kinds of ：

Basic group ( Private group )： When establishing an account , If the group to which the account belongs is not specified , The system will create a group with the same user name , this The first group is the basic group .

Additional group ( Public group )： Can accommodate multiple users , All users in the group have the rights owned by the group .

linux Which file stores user information in ？ And what do the fields mean

/etc/passwd（ User account file , All accounts are accessible ） A total of 7 paragraph , The format is as follows ：

user name ： password ：UID：GID： Account information ： Account directory ：Shell type

/etc/shadow（ User password file ,root To access ）, A total of 9 paragraph , The format is as follows ：

user name ： password ： The number of days of the last modification time ： The minimum interval between two password changes ： How many days later, you need to change your password again ： The number of days from issuing a warning to the official expiration of the password ： The number of days that the user name is still valid before login is prohibited ： The time when the user is forbidden to log in ： Flag fields , meaningless

linux What is the file in which the group information is stored ？ And what do the fields mean ？

/etc/group（ User group file , All accounts are accessible ）, A total of 4 paragraph , The format is as follows ：

User group name ： Set the password ：GID： The group members

 2. Create the following users 、 Groups and group membership ：
 1. Create a sysmgrs Group
 2. Create user natasha At the same time specified sysmgrs As natasha Additional groups of

 3. Create user harry At the same time specified sysmgrs As harry Additional groups of
 4. Create user sarah Appoint shell The type is /sbin/false( You do not have access to interactive on the system shell)
  It's not sysmgrs Members of

5. Set up natasha 、 harry and sarah All of your passwords are 123

 6. Create user lockuser, And specify home directory as /home/lock, Then lock the user

 7. Create user limituser, gid by 1555,userid by 1666, Let its password in 10 Expires in days

 

 

 8. Unlock lockuser, And set that the password must be changed the next time you log in

 9. Give Way natasha With modification harry Password permissions (sudo)

 10. Create user testuser And set the password , Change the user name to normaluser   

 11. Delete lockuser

 3. create a file , And give authority 611( Two ways , A kind of guoa, A kind of nnn)

 4. Create directory , And give authority 755( Two ways , A kind of guoa, A kind of nnn)

 5. create a file , And modify the owner and group of the file to other users

 6. Set up suid, Set for file suid( Two ways u+s and nnnn) The way

 7. Set up sgid, Set for file sgid( Two ways g+s and nnnn) The way

 8. Set up sbit, Set for directory sbit( Two ways o+t and nnnn) The way

 9. create a file , Query file acl
    Set for file acl The user is testuser1 Permission is rwx

  Set for file acl Of mask: Permission is r-x