User Accounts
Introduction
Creation and management of users and user groups is one of the fundamental pieces of system administration on multi-user systems such as Linux. The user accounts system provides a secure storage area for users' files and gives users the ability to customize their working environment according to their needs.
Fedora includes two types of accounts - system and non-system accounts. System accounts includes the root user and other system accounts, such as the apache user, that are created during the installation process and used by various system daemons and utilities to perform system-wide tasks. Fedora reserves the first 499 uids for system accounts. This is why they are sometimes reffered to as low ID accounts.
Non-system accounts start from uid 500 and are used for regular users to perform their day-to-day, non-privileged tasks. Usually, the first user account is created during the first boot following the system's installation. After that, user and group accounts can be created with standard procedures.
Ways to Create and Modify User and Group Accounts
As with most other tasks, system administrator can chose between two ways of creating and subsequently modifying user accounts:
- Command line interface
- Graphical interface
To start explaining the process that happens in the background during account creation, following tables show listing of the programs used by system administrator and files manipulated in the course of this process:
| Command Line Programs | ||
|---|---|---|
| Program Executable | Location in the File System | Purpose |
useradd |
/usr/sbin/useradd |
Creates user account |
usermod |
/usr/sbin/usermod |
Modifies user account |
groupadd |
/usr/sbin/groupadd |
Creates group account |
groupmod |
/usr/sbin/groupmod |
Modifies group account |
passwd |
/usr/bin/passwd |
Sets or changes user's password |
chage |
/usr/bin/chage |
Changes password expiry information |
Table 1.1 - Command Line Programs
| Graphical Interface Program | ||
|---|---|---|
| Program Executable | Location in the File System | Purpose |
system-config-users |
/usr/bin/system-config-users |
Creates and modifies user and group accounts |
| System > Administration > Users and groups | /usr/bin/system-config-users |
Creates and modifies user and group accounts |
Table 1.2 - Graphical Interface Program
Top raw indicates how to invoke the program from the command line interface. The result is the same as if running program using its icon in the System menu.
| Files Containg User and Group Data and Accounts Settings | |
|---|---|
| Absolute Path / File Name | Purpose |
/etc/passwd |
Contains essential information about users such as username, password (if shadow passwords are not used), uid, gid of the user's primary group, location of the user's home directory, user's default shell, etc. |
/etc/shadow |
Contains user's encrypted password and information related to password policies, such as password age and expiration time |
/etc/group |
Contains group's name, group's password (if shadow passwords are not used), group's numerical ID (gid) and list of group members |
/etc/gshadow |
Contains group's name, group's encrypted password (if set), group administrators and group members |
/home/<username> |
This is default location for the user's home directory |
/etc/skel/* |
Hidden files for user's shell environment configuration |
Table 1.3 - Files and Directories Containing User and Group information
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