> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Privilege Escalation

> This article explains how to use sudo for privilege escalation on Linux, enhancing security by allowing controlled access to superuser commands.

Privilege escalation allows a non-root user to perform tasks requiring superuser rights. Instead of enabling direct root logins—which poses security risks—you can delegate specific commands to trusted users via `sudo`. This approach enforces the [principle of least privilege](https://en.wikipedia.org/wiki/Principle_of_least_privilege) and keeps your system secure.

## Why Use sudo?

* Grants temporary elevated rights without sharing the root password
* Provides an audit trail of executed commands
* Limits users to only the commands they need

### Attempting a Restricted Operation

Without `sudo`, installing packages fails:

```bash theme={null}
$ apt install nginx
E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
```

### Elevate with sudo

Prepend `sudo`, authenticate with your own password, and the command succeeds:

```bash theme={null}
$ sudo apt install nginx
[sudo] password for michael: 
```

<Callout icon="lightbulb" color="#1CB2FE">
  If you see `User michael is not in the sudoers file`, add your user to the `sudo` group or update `/etc/sudoers` accordingly.
</Callout>

## Configuring sudo: /etc/sudoers

All `sudo` policies live in `/etc/sudoers` and included files under `/etc/sudoers.d/`. Always edit with `visudo` to prevent syntax errors:

```bash theme={null}
sudo visudo
```

Here’s a sample excerpt:

```bash theme={null}
# User privilege specification
root    ALL=(ALL:ALL) ALL

# Members of the admin group may gain root privileges
%admin  ALL=(ALL)       ALL

# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL)   ALL

# Allow mark to run any command
mark    ALL=(ALL:ALL)   ALL

# Allow sarah to reboot the system
sarah   localhost=/usr/bin/shutdown -r now

# See sudoers(5) for more information on "#include" directives:
#includedir /etc/sudoers.d
```

| Field                | Description                                           | Example                          |
| -------------------- | ----------------------------------------------------- | -------------------------------- |
| User or Group        | Username (e.g., `mark`) or group (`%sudo`)            | `%admin`                         |
| Host(s)              | Hosts where the rule applies (usually `ALL`)          | `localhost`                      |
| Run-As Specification | User and group for command execution (in `(` and `)`) | `(ALL:ALL)`                      |
| Commands             | Allowed commands or `ALL` for full rights             | `/usr/bin/shutdown -r now`       |
| Comments             | Lines beginning with `#` are ignored                  | `# User privilege specification` |

<Callout icon="triangle-alert" color="#FF6B6B">
  Never edit `/etc/sudoers` with a regular text editor. Syntax errors can lock out all sudo access. Always use `visudo`.
</Callout>

## Best Practices for sudo Configuration

* Grant only the commands necessary for a task
* Use group-based rules to simplify management
* Avoid `NOPASSWD` unless automation requires it
* Keep custom rules in `/etc/sudoers.d/` for modularity

## Hands-On Exercises

1. Create a test user:
   ```bash theme={null}
   sudo useradd -m bob
   sudo passwd bob
   ```
2. Add the user to the `sudo` group:
   ```bash theme={null}
   sudo usermod -aG sudo bob
   ```
3. Switch to `bob` and install a package:
   ```bash theme={null}
   su - bob
   sudo apt update && sudo apt install htop
   ```
4. Customize a rule in `/etc/sudoers.d/custom_rules` to allow `bob` to restart services without a password.

## Links and References

* [sudo Manual Page](https://www.sudo.ws/man/1.8.31/sudoers.man.html)
* [Visudo Documentation](https://linux.die.net/man/8/visudo)
* [Principle of Least Privilege](https://en.wikipedia.org/wiki/Principle_of_least_privilege)
* [Kali Linux Privilege Escalation Guide](https://www.kali.org/docs/practice/privilege-escalation/)

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