# LFCS: Users and Groups (10%)

This document covers user and group management, environment profiles, ACLs, resource limits, and LDAP integration.

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## Goals Coverage

### Users and Groups 10%
1) Create and manage local user and group accounts
2) Manage personal and system-wide environment profiles
3) Configure user resource limits
4) Configure and manage ACLs
5) Configure the system to use LDAP user and group accounts

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## 1. Create and Manage Local User Accounts

### Learn

* Add, modify, and delete local users.
* Manage home directories and shells.

### Commands

```bash
# Add user
sudo useradd -m -s /bin/bash username
sudo passwd username

# Modify user
sudo usermod -aG sudo username   # Add to group
sudo usermod -d /new/home username  # Change home directory

# Delete user
sudo userdel -r username   # Delete user and home directory
```

### Exercises

1. Create a user with home directory and bash shell.
2. Add the user to the sudo group.
3. Remove a test user.

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## 2. Create and Manage Groups

### Learn

* Create, modify, and delete groups.
* Assign users to groups.

### Commands

```bash
# Create group
sudo groupadd developers

# Modify group
sudo gpasswd -a username developers

# Delete group
sudo groupdel developers

# List groups
groups username
```

### Exercises

1. Create a group `admins` and add a user.
2. Verify the user is part of the group.
3. Delete the group.

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## 3. Manage Environment Profiles

### Learn

* System-wide vs user-specific profiles.
* Configure PATH, variables, and shell startup files.

### Commands

```bash
# Edit system-wide profile
sudo nano /etc/profile
sudo nano /etc/bash.bashrc

# Edit user profile
nano ~/.bashrc
source ~/.bashrc  # Reload changes
```

### Exercises

1. Add a directory to PATH in `.bashrc` and reload.
2. Set a custom environment variable system-wide.

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## 4. Configure User Resource Limits

### Learn

* Use `ulimit` and `/etc/security/limits.conf` for limits on processes, open files, and memory.

### Commands

```bash
# Temporary limit
ulimit -n 4096

# Persistent limit
sudo nano /etc/security/limits.conf
# user soft nofile 4096
# user hard nofile 8192
```

### Exercises

1. Increase the maximum number of open files for a user.
2. Verify limits with `ulimit -a`.

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## 5. Configure and Manage ACLs (Access Control Lists)

### Learn

* Set fine-grained permissions beyond standard Unix mode bits.
* Commands: `getfacl` and `setfacl`.

### Commands

```bash
# Check ACL
getfacl /path/to/file

# Set ACL for user
setfacl -m u:username:rwx /path/to/file

# Remove ACL
setfacl -x u:username /path/to/file
```

### Exercises

1. Give read/write access to a specific file for a user without changing group ownership.
2. Remove the ACL and verify permissions.

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## 6. Configure the System to Use LDAP for Users and Groups

### Learn

* Integrate Linux system with LDAP server for centralized authentication.
* Configure NSS and PAM.

### Commands

```bash
# Install LDAP client
sudo apt install libnss-ldap libpam-ldap ldap-utils

# Configure /etc/nsswitch.conf
sudo nano /etc/nsswitch.conf
# passwd: files ldap
group: files ldap
shadow: files ldap

# Test LDAP user
getent passwd ldapuser
id ldapuser
```

### Exercises

1. Connect a Linux system to an LDAP server.
2. Verify that LDAP users can login.

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## Exam Tips

* Practice creating users and groups both locally and via LDAP.
* Understand persistent vs temporary environment variable settings.
* Familiarize with ACL commands for fine-grained permission control.

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