Account command and account authority

Account base command

• Display host name

hostname 

// Change host name 
hostname abc

• Check the current location

pwd

• View user login information

who

• User login details

w

• View current account

whoami

• View system time 、linux The elapsed time 、 Number of users 、 Load condition

uptime  

• View the current account UID \ GID

id

• Switch accounts

The administrator can directly switch to the general account , Common account needs password to switch to administrator

1.su   Account name 
2.su  Default switch administrator 

• Add account

useradd  Account name 

 Parameters 
-u： Set up UID
-g： Set primary group 
-G： Set the group to be affiliated 
-C： Set the user instructions 
-d： Specify user home directory 
-S： Designated user shell
-e： Account expiration date , The format is : YYYY-MM-DD
-f： Specifies whether the password is invalid ,0 Indicates immediate failure ,1 It means never to fail 

Used useradd after , The following operations will be performed by default
1、 stay /etc/passwd Next Establish relevant information
2、 stay /etc/shadow Write the relevant parameters of the password
3、 stay /etc/group Write in Enter a group with the same account name
4、 stay /home Create the user's home directory under

• Delete account

userdel  Account name 

 Parameters 
-r： Delete along with home directory and email 

 To completely delete an account , step :
1、 Delete /etc/passwd;/etc/shadow Contents of the file 
2、 Delete /etc/group;/etc/gshadow
3、 Delete /home/username;/var/spool/ mail/username
4、 Delete the user who has been to this Liunx Files created in ,find To search , In the use of userdel

• Modify account information

usermod 

 Parameters 
-C： Account description 
-d： Modify home directory 
-g： Modify the primary group 
-G： Modify affiliate group 
-a： And -G- - Start using , Add affiliate groups 
-l： Change user name 
-U： modify UID
-L： Frozen account 
-U： thaw 

• Set the password

passwd   password 

 Parameters 
-l： Lock the account   / Also available at /etc/shadow in   Add... To the place where you put the password !
-U： Unlock 
-S： Display the password parameters of the account 
-n： Number of days to go , Set how long you can not change your password .
-X： Number of days to go , Set how long the password must be changed 
-W： Number of days to go , Set the number of warning days before password expiration 
-i： Number of days to go , Set password expiration days 

• Set the time related parameters of the password

chage 

 Parameters 
-L： View the time parameters related to an account and password 
-d：YYYY-MM-DD, Change the time when the password was last changed 
-E：YYYY-MM-DD, Modify the expiration time of the account 
-l： Days , The password will expire after a few days 
-m： Days , Set the password for at least a few days ,
-M： Days , How long after setting the password , You need to update 
-W： Days , Set the warning time before password expiration 

Little knowledge

chage -d 0 Account name //-d Back plus 0 , The purpose is to force you to change your password when you log in to this account for the first time , This password must conform to the complexity specification （ Capitalization 、 A lowercase letter 、 Numbers 、 character ）

Account on disk

Account and group name ： People see it

UID and GID:：Linux see Of

id： View the currently logged in user's UID and GID

When we use Is -I When , The system will /etc/passwd and /etc/ group The content of the document , find UID and GID The corresponding name

1. /etc/passwd： Recorded Linux All accounts on
2. /etc/shadow： The password corresponding to the account is recorded
3. /etc/group： All groups are recorded

• /etc/passwd
  

1. 123： user name
2. X： In the early part of this section, the user login password , Now the password is put in /etc/shadow It's in
3. UID： 0 Indicates that the system administrator ,1-999 Protect Reserved for the system ID,1000 With For general users
4. GID：0 Indicates that the system administrator ,1-999 Protect Reserved for the system ID,1000 With , For general users
5. Lewis： User information description ,/home/lewis: User home directory , When logging in , directory /bin/bash, When the user logs in , Whether it can be used shell, If you can't use shell, Is displayed /sbin/ nologin

• /etc/shadow

1. 123： Use the corpse name
2. A string of red characters ： Encrypted password .
3. Date of last password change ：Linux Date in , It's through 1970 year 1 month 1 The date on which the accumulation begins
4. The number of days that the password cannot be changed ：0 It means that it can be modified at any time
5. The number of days that the password needs to be changed again ： By modifying the value , You can force users to change passwords
6. Number of alarm days for password change ：7 The system will send an alarm to the user within days
7. After password expiration , How long can the account still be used
8. Account expiration date ： adopt 1970 year 1 month 1 The date on which the accumulation begins , When it's time , Whether or not the password has expired , The account can no longer be used
9. Retain

• /etc/group
  

1. Lewis： Group name
2. X： Set the password , In general, you don't need
3. 1000：GID
4. Affiliate group , These documents are not recommended to be modified directly , It is recommended to use the command to modify .