1. Understand the configuration files closely related to users:
/etc/passwd : stores some basic information of all users on the system, such as username, UID, GID, home directory and default shell, etc.
/etc/shadow : Stores the passwords of all users on the system (encrypted form) and some account security-related settings, such as password change dates, etc.
/etc/group : Stores information about all user groups on the system. Each line contains a group name, the group's GID, and a list of users who belong to the group.
These three profiles are the ones most closely related to the user, but there are some other related profiles:
/etc/login.defs: Stores default parameters related to login, such as account lockout time, password policy, etc.
/etc/default/useradd: Stores default parameters for creating new users, such as home directory location, default shell, etc.
/etc/skel: The files and directories that are automatically copied when new users are created are stored under the directory.
/etc/spool/mail: store user's mailbox
2. The background work of the user command:
3. Configuration steps ( using super administrator privileges )
3.1 vim /etc/passwd
Enter the file, first add some basic information of the user, I will name the name of the user to be added as jack
Annotation for each column of user information:
3.2 vim /etc/shadow
Enter the file, set the user password, user password usage time, expiration reminder and other information
Notes for each column:
3.3 vim /etc/group
Configure the main group of jack Configure the main group of jack as wudangpai
Annotation for each column:
3.4 Create a new home directory
mkdir /home/jack
3.5 Copy the environment variable initialization script to the home directory
cp /etc/skel/.* /home/jack/3.6 Create a new mailbox
touch /var/spool/mail/jack
3.7 Modify the permissions related to the home directory
chown jack:wudangpai /home/jack/
chmod 700 /home/jack/
3.8 Modify mailbox-related permissions
chmod 660 /var/spool/mail/jack
chown jack:mail /var/spool/mail/jack
After completing the above steps, a common user is successfully created manually
3.9 Testing
You can use the su - jack command to switch to the jack user
4. shell start
4.1 Two ways to start the shell
4.2 Differences between shell startup configuration files
5. Pay attention
Before modifying these configuration files, it is strongly recommended to back them up. In general, these files can be automatically updated through commands that manage a user (eg useradd, , passwdand , usermodetc.).