In Linux system, using the usermod command to add users to the secondary group is: 1. Execute the sudo usermod -a -G group name username command to add, where -a means append to avoid overwriting the original secondary group; 2. Use groups username or grep group name /etc/group to verify whether the operation is successful; 3. Note that the modification only takes effect after the user logs in again, and the main group modification should use the -g parameter; 4. You can also manually edit the /etc/group file to add users, but be careful to avoid system abnormalities caused by format errors.
In Linux systems, adding users to a secondary group is a common operation, especially when managing permissions and sharing resources. The method to achieve this goal is not complicated, but you need to pay attention to how the commands are used and the system environment.
Use the usermod
command to add users to secondary groups
This is the most commonly used method for most mainstream Linux distributions such as Ubuntu, CentOS, and Debian.
-
Basic command format:
sudo usermod -a -G group name username
in:
-
-a
means "append", which means appending to an existing group, not a replacement. -
-G
means specifying the secondary group (note that it is capital G). - If
-a
is not added, other secondary groups that the user currently belongs to will be cleared!
-
For example:
Want to add user
alice
to thedevelopers
group:sudo usermod -a -G developers alice
Verification is successful:
You can use the following command to view all groups to which the user belongs:
groups alice
Or view the corresponding group information in the
/etc/group
file:grep developers /etc/group
Notes on modifying user groups
Although the operation is simple, some details are prone to errors or are ignored in actual use:
Administrator permissions are required :
sudo
permissions are usually required to executeusermod
.Effective time issue : After the user's group information is changed, it will only take effect after logging in again . In other words, what you see in the current terminal session is still the old group information.
How to deal with multiple groups? : Multiple groups can be added at once, separated by commas:
sudo usermod -a -G group1,group2 username
Don't misuse the
-g
parameter : that is used to modify the primary group, not the secondary group.
Alternative: Manually edit /etc/group
If you prefer to edit the configuration file directly, you can also manually modify the /etc/group
file to add users to the group.
Open the file:
sudo nano /etc/group
Find the group name you want to modify, for example:
developers:x:1001:bob
Append the username and become:
developers:x:1001:bob,alice
Save and exit.
?? This method is suitable for people who are familiar with text editing and system structure. It is prone to system abnormalities due to spelling errors or formatting problems , so it is recommended to use
usermod
first.
Basically that's it. Just remember the key points: use usermod -a -G
to add secondary groups, don't miss -a
, remember to let the user log in again after the modification.
The above is the detailed content of How to add a user to a secondary group?. For more information, please follow other related articles on the PHP Chinese website!

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In Linux system, using the usermod command to add users to the secondary group is: 1. Execute the sudousermod-a-G group name username command to add, where -a means append to avoid overwriting the original secondary group; 2. Use groups username or grep group name /etc/group to verify whether the operation is successful; 3. Note that the modification only takes effect after the user logs in again, and the main group modification should use the -g parameter; 4. You can also manually edit the /etc/group file to add users, but be careful to avoid system abnormalities caused by format errors.

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