To manage Linux user groups, you need to master the operation of viewing, creating, deleting, modifying, and user attribute adjustment. To view user group information, you can use cat /etc/group or getent group, use groups [username] or id [username] to view the group to which the user belongs; use groupadd to create a group, and use groupdel to specify the GID; use groupdel to delete empty groups; use usermod -aG to add users to the group, and use usermod -g to modify the main group; use usermod -g to remove users from the group by editing /etc/group or using the vigr command; use groupmod -n (change name) or groupmod -g (change GID) to modify group properties, and remember to update the relevant file permissions.
Managing user groups in Linux systems is a basic but important task in system management. Whether it is adding, deleting groups, or adjusting the group permissions to which the user belongs, certain operation skills and understanding are required. Here are some practical methods and suggestions to help you better manage user groups in Linux.
View user groups in the current system
User group information in Linux is mainly stored in /etc/group file. You can directly use cat /etc/group to view all groups and their members.
The more commonly used commands are:
-
getent group: Displays all groups (including those obtained through network services such as LDAP) -
groups [用戶名]: View the group to which a user belongs -
id [用戶名]: View the user's UID, GID and group
These commands can help you quickly understand the current system's group structure and user attributes.
Create and delete user groups
Creating a new user group is very simple, just use the groupadd command:
sudo groupadd newgroup
If you want to specify a GID (group ID), you can add the -g parameter:
sudo groupadd -g 1010 newgroup
To delete an empty group (group without members) you can use groupdel :
sudo groupdel newgroup
Note: If the group has been set as the default group by a user, it cannot be deleted directly. You need to modify or delete the relevant user account first.
Add or remove a user to or from a group
To add an existing user to a group, you can use the usermod command:
sudo usermod -aG groupname username
Here -aG means "append" to the specified group without affecting the user's existing permissions for other groups.
If you just want to modify the user's primary group, you can omit -a :
sudo usermod -g groupname username
To remove a user from a group, there is no direct command, you can manually delete the user name by editing the /etc/group file, or use one of the following methods:
- Use the
vigrcommand to safely edit group files - Automate processing with scripts or tools (for batch operations)
Modify the properties of an existing group
Use the groupmod command to modify the name or GID of the group:
sudo groupmod -n newname oldname sudo groupmod -g 1020 groupname
After modifying the group name or GID, remember to check whether there are files or directories in the system that belong to the old GID and update the permissions accordingly:
find / -group oldgid -exec chgrp newgid {} \;Basically that's it. By mastering these basic commands, you can manage and maintain user groups in Linux systems well. Although it doesn't seem complicated, slight negligence may also cause permission problems, especially in environments where multiple people collaborate or multi-service operation, it is best to confirm clearly before operation.
The above is the detailed content of How to manage groups on Linux. For more information, please follow other related articles on the PHP Chinese website!
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