User Management in Linux¶
A user account in Linux is an identity used to access and interact with the system. It defines permissions, ownership of files, and access to system resources.
User Accounts Attributes¶
| Attribute | Location (Field/Line) | Description |
|---|---|---|
| Username | /etc/passwd → 1st field | Unique name identifying the user. |
| User ID (UID) | /etc/passwd → 3rd field | Numeric identifier for the user. |
| Group ID (GID) | /etc/passwd → 4th field | Primary group ID associated with the user. |
| Supplementary Groups | /etc/group → lines where user appears | Additional groups the user belongs to. |
| Home Directory | /etc/passwd → 6th field | Default directory assigned to the user. |
| Shell | /etc/passwd → 7th field | Default command-line interpreter (e.g., /bin/bash). |
| Password (hashed) | /etc/shadow → 2nd field | Encrypted password for authentication. |
| Account Expiry Date | /etc/shadow → 8th field | Date when the account becomes inactive. |
| Password Expiry Date | /etc/shadow → 5th field | Date when the password must be changed. |
| Minimum Password Age | /etc/shadow → 3rd field | Minimum days before password can be changed. |
| Maximum Password Age | /etc/shadow → 4th field | Maximum days before password must be changed. |
| Password Warning Period | /etc/shadow → 6th field | Days before expiry to warn user. |
| Inactive Period | /etc/shadow → 7th field | Days after password expiry before account is disabled. |
| Account Status | passwd -S → output status field | Indicates if account is active or locked. |
| Login History | last → lines per login event | Records of user logins. |
| Failed Login Attempts | faillog → per-user entry | Tracks unsuccessful login attempts. |
| Full Name (GECOS) | /etc/passwd → 5th field | User’s full name and optional info (comma-separated). |
| Email Address | GECOS or external systems | Can be manually added or managed via LDAP/email systems. |
| Office Location | /etc/passwd → GECOS field (2nd item) | Optional field for user’s office location. |
| Work/Home Phone | /etc/passwd → GECOS field (3rd/4th items) | Optional phone numbers. |
| Custom Metadata | LDAP or external identity systems | Additional attributes like department, title, etc. |