To manage Linux users, you need to master the basic concepts and key commands of users and groups. Add useradd commands commonly used by new users, such as sudo useradd alice, or use the -m parameter to automatically create home directories, which is easier to use the adduser command. Modify permissions can be added to the attached group through usermod -aG, or join the sudo group to grant administrator permissions. Use userdel to delete users, add -r to clean up the home directory at the same time, and disable the account to lock with passwd -l. Use id, getent passwd, groups and other commands to view information, and regularly check password-free accounts to ensure security.
Managing Linux users is actually not too difficult, but it is easy for novices to mess up the steps or fail to set permissions. The focus is on understanding the basic concepts of users and groups, and mastering several key commands. Below I will explain how to do it according to common needs in several parts.
Add new users
The useradd
command is the most commonly used user to add users in Linux systems. For example, if you want to add a user called alice, you can do this:
sudo useradd alice
By default, this user will not have a home directory (/home/alice) immediately, nor will he set a password. You need to manually create the home directory and set the initial password:
- Create home directory:
sudo mkdir /home/alice
- Copy the default configuration file into:
sudo cp /etc/skel/. /home/alice/
- Set password:
sudo passwd alice
You can also use the -m
parameter to automatically create a home directory, like this:
sudo useradd -m alice
An easier way is to use the adduser
command (available on Debian/Ubuntu systems) and it will automatically help you with these steps.
Modify user permissions and attributes
Each user has his or her own main group, and can also join multiple additional groups. For example, if you have a development group dev and want alice to join, you can use:
sudo usermod -aG dev alice
Here -aG
means "append to a certain group". If you use usermod -G dev alice
directly, the other groups that alice belongs to before will be cleared and only dev will be retained.
Sometimes you may need to give the user temporary administrator privileges, which can be added to the sudo group:
sudo usermod -aG sudo alice
After that, alice can execute administrator commands through sudo
.
Delete or disable users
Deleting a user is not just running userdel
. By default:
sudo userdel alice
It will only delete the user's account, and will not delete files such as her home directory and email. If you want to clean up together, add the -r
parameter:
sudo userdel -r alice
If you just don't want her to log in for the time being, you can lock your account:
sudo passwd -l alice
To unlock:
sudo passwd -u alice
View and maintain user information
To view user information, these commands are mainly used:
-
id alice
: View the user's UID and group -
getent passwd
: List all users -
cat /etc/passwd
: It also looks at the user list, but may include system users -
groups alice
: see which groups the user belongs to
Also, remember to check regularly for unnecessary users, especially those service accounts that are automatically created. You can use the following command to see which accounts without passwords are available:
awk -F: '($2 == "") {print}' /etc/shadow
Such accounts may have security risks, so it is best to set a password or lock it.
Basically these are the operations. Linux user management seems to have many steps, but in fact each step is clear. The key is not to miss permission settings and cleaning.
The above is the detailed content of How to manage users on Linux. For more information, please follow other related articles on the PHP Chinese website!

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