Howto: Linux Add User To Group
2014-11-10 13:02
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How can I add a user to a group under Linux operating system using command line options? How to add an existing user into a group in Linux using command line options?
You can use the useradd or usermod commands to add a user to a group. The useradd command creates a new user or update default new user information. The usermod command modifies a user account and it is useful to add user to existing groups.
There are two types of groups under Linux operating systems:
Primary user group.
Secondary or supplementary user group.
All user account related information are stored in the following files:
/etc/passwd - Contains one line for each user account.
/etc/shadow - Contains the password information in encrypted formatfor the system's accounts and optional account aging information.
/etc/group - Defines the groups on the system.
/etc/default/useradd - This file contains a value for the default group, if none is specified by the useradd command.
/etc/login.defs - This file defines the site-specific configuration for the shadow password suite stored in /etc/shadow file.
In this example, create a new user called vivek and add it to group called developers. First login as a root user (make sure group developers exists), enter:
Output:
If you do not see any output then you need to add group developers using the groupadd command:
Next, add a user called vivek to group developers:
Setup password for user vivek:
Ensure that user added properly to group developers:
Please note that capital G (-G) option add user to a list of supplementary groups. Each group is separated from the next by a comma, with no intervening whitespace. For example, add user jerry to groups admins, ftp, www, and developers, enter:
Sample outputs:
Please note that small g (-g) option add user to initial login group (primary group). The group name must exist. A group number must refer to an already existing group.
-a option ~ i.e. add the user to the supplemental group(s). Use only with
-G option:
In this example, change tony user's primary group to www, enter:
How can I add a user to a group under Linux operating system using command line options? How to add an existing user into a group in Linux using command line options?
You can use the useradd or usermod commands to add a user to a group. The useradd command creates a new user or update default new user information. The usermod command modifies a user account and it is useful to add user to existing groups.
There are two types of groups under Linux operating systems:
Tutorial details | |
---|---|
Difficulty | Intermediate (rss) |
Root privileges | Yes |
Requirements | usermod/useradd |
Estimated completion time | 5 minutes |
Secondary or supplementary user group.
All user account related information are stored in the following files:
/etc/passwd - Contains one line for each user account.
/etc/shadow - Contains the password information in encrypted formatfor the system's accounts and optional account aging information.
/etc/group - Defines the groups on the system.
/etc/default/useradd - This file contains a value for the default group, if none is specified by the useradd command.
/etc/login.defs - This file defines the site-specific configuration for the shadow password suite stored in /etc/shadow file.
useradd Example - Add a new user to secondary group
You need to the useradd command to add new users to existing group (or create a new group and then add user). If group does not exist, create it. The syntax is as follows:useradd -G {group-name} username
In this example, create a new user called vivek and add it to group called developers. First login as a root user (make sure group developers exists), enter:
# grep developers /etc/group
Output:
developers:x:1124:
If you do not see any output then you need to add group developers using the groupadd command:
# groupadd developers
Next, add a user called vivek to group developers:
# useradd -G developers vivek
Setup password for user vivek:
# passwd vivek
Ensure that user added properly to group developers:
# id vivekOutput:
uid=1122(vivek) gid=1125(vivek) groups=1125(vivek),1124(developers)
Please note that capital G (-G) option add user to a list of supplementary groups. Each group is separated from the next by a comma, with no intervening whitespace. For example, add user jerry to groups admins, ftp, www, and developers, enter:
# useradd -G admins,ftp,www,developers jerry
useradd example - Add a new user to primary group
To add a user tony to group developers use the following command:# useradd -g developers tony # id tony
Sample outputs:
uid=1123(tony) gid=1124(developers) groups=1124(developers)
Please note that small g (-g) option add user to initial login group (primary group). The group name must exist. A group number must refer to an already existing group.
usermod example - Add a existing user to existing group
Add existing user tony to ftp supplementary/secondary group with the usermod command using the-a option ~ i.e. add the user to the supplemental group(s). Use only with
-G option:
# usermod -a -G ftp tony
In this example, change tony user's primary group to www, enter:
# usermod -g www tony
usermod command options summary
Option | Purpose |
---|---|
-a --append | Add the user to the supplementary group(s). Use only with the -G option. |
-g GROUP --gid GROUP | Use this GROUP as the default group. |
-G GRP1,GRP2 --groups GRP1,GRP2 | Add the user to GRP1,GRP2 secondary group. |
A note about security
If you add or delete user to existing group, you must change the owner of any crontab files or at jobs manually. You must make any changes involving NIS on the NIS server too.相关文章推荐
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