Users and groups
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The document provides an overview of user and group management in Red Hat Enterprise Linux (RHEL), detailing how users are identified by unique user IDs (UIDs) and assigned to groups. It explains permissions, group IDs (GIDs), and commands for creating and modifying users and groups through the command line. Key commands include adding, modifying, locking, unlocking, and deleting users, as well as managing group memberships.
Users and groups
- 1. By – Varnnit Jain 9990888972 Users And Groups In RHEL
- 2. Users Every person that logs into the computer is considered as a user. Every user is assigned a unique user ID number (UID). UID 0 identifies root. User acccounts usually starts at UID 500. 1-499 UID is reserved for the system users. Whenever you create any user in Linux It belongs to their own group. User names and UIDs are stored in /etc/passwd. Users are assigned a home directory ( /home/username) and a program that is run when they log in. (Usually a shell)
- 3. USERS Users have full access to their directories. User cannot read, write or execute each other files without permission.
- 4. GROUP A group is a collection of users which make easy for administration to perform the task of administration level. When they need to apply permissions and restrictions with the same level to many users , the such permissions an restrictions can be applied to related groups. Users are assigned to groups . Every user is a member of at least one group and possibly more. Each group is assigned a unique group ID number (GID).
- 5. GROUP Each group is given their own private group (primary group, usually the same name of the user). Users can be added to other groups. User’s primary group is defined in the /etc/passwd file. User’s secondary group is defined in the /etc/group file. All users in a group can share files that belong to that user.
- 6. In Command Line #adduser username : Create a new user. #passwd username : Change/set password for user. #groupadd groupname: create a new group. #gpasswd groupname : Set Group Password. #usermod –g groupname user name ,:Change the primary group of the user #usermod –G groupname username : Create a secondary group for a user. #usermod –a G groupname username : join user in multiple secondary group but more steps are required.
- 7. #usermod –l username : Lock user. #usermod --lock username : lock user. #passwd -S username : Want to see if the user is ocked or not. #usermod –U username : Unlock user. #usermod –unlock username : Unock user. #userdel –r username : Delete user wih its directory. #usermod –l newname oldname : Rename the user. #gpasswd –a username groupname : Add user to groups. #gpasswd –d username groupname : Remove user from group.
- 8. Example 1. #adduser varnnit 2. #passwd varnnit. 2. #groupadd varnnitjain ; gpasswd varnnitjain
- 9. 3. A new user has been added.
- 10. 4. #usermod –aG group_name user_name This command is used to add a user to a secondary group.
- 11. . 5. #usermod –L username 6. #passwd –S username 7. #usermod –U username
- 12. 8. #userdel –r username
- 13. 9. #usermod –l new_name old_name
- 14. 10. Usermod –e expire_date user_name 11. #gpasswd –a user_name group_name