> ## 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.

# Update software to provide required functionality and security

> This article explains how to use the DNF package manager on CentOS Stream to update software for security and functionality.

Keeping your Linux system up to date is critical—most online attacks exploit known vulnerabilities in outdated software. In this guide, you’ll learn how to use the DNF package manager on CentOS Stream (and other RHEL‐based distributions) to check for updates, apply upgrades, and reboot when necessary.

<Callout icon="lightbulb" color="#1CB2FE">
  Regular updates not only patch security holes but also introduce new features and performance improvements.
</Callout>

## Package Management with DNF

DNF (Dandified YUM) handles software installations, removals, and upgrades on CentOS Stream 8 and similar distributions. Before applying updates, always list the packages that have newer versions available.

### Checking for Available Updates

Run the following command to see which packages can be updated:

```bash theme={null}
dnf check-update
```

Sample output:

```bash theme={null}
CentOS Stream 8 - AppStream                         11 kB/s |  4.4 kB     00:00
CentOS Stream 8 - BaseOS                            14 kB/s |  3.9 kB     00:00
CentOS Stream 8 - Extras                            7.5 kB/s |  3.0 kB     00:00

Installing:
 kernel                          x86_64  4.18.0-348.2.1.el8_5   baseos   7.0 M
 kernel-devel                    x86_64  4.18.0-348.2.1.el8_5   baseos  20 M
 alsa-sof-firmware.noarch        1.9-1.el8                       baseos 
 bpftool.x86_64                  4.18.0-348.2.1.el8_5           baseos
 device-mapper.x86_64            8:1.02.181-1.el8                baseos

Obsoleting Packages
 kernel-headers.x86_64           4.18.0-348.2.1.el8_5            baseos
 kernel-headers.x86_64           4.18.0-348.el8                  @baseos
```

This output categorizes packages that will be installed, upgraded, or removed.

## Upgrading All Out‐of‐Date Packages

To perform a full system upgrade, use:

```bash theme={null}
sudo dnf upgrade
```

You’ll receive a transaction summary like this:

```bash theme={null}
Transaction Summary
================================================================================
 Install  4 Packages
 Upgrade  17 Packages

Total download size: 137 M
Is this ok [y/N]:
```

* **Install**: New dependencies required by updated packages
* **Upgrade**: Packages being replaced with newer versions

Type `y` and press Enter to proceed.

<Callout icon="triangle-alert" color="#FF6B6B">
  Pay attention to the download size and package count. Large upgrades on production servers may require scheduled maintenance windows.
</Callout>

## Reboot After Core Updates

Upgrading the kernel, system services, or libraries often requires a reboot. To apply these changes, reboot the system:

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

<Callout icon="lightbulb" color="#1CB2FE">
  Always verify critical services after rebooting to ensure they’ve started correctly.
</Callout>

## Summary of Common Commands

| Command            | Purpose                                  |
| ------------------ | ---------------------------------------- |
| `dnf check-update` | List all packages with available updates |
| `sudo dnf upgrade` | Upgrade every out‐of‐date package        |
| `sudo reboot`      | Restart the system to load core updates  |

## Links and References

* [CentOS Stream Documentation](https://docs.centos.org/en-US/stream/)
* [DNF Package Manager Guide](https://dnf.readthedocs.io/)
* [Linux Security Best Practices](https://www.kernel.org/doc/html/latest/admin-guide/security.html)

<CardGroup>
  <Card title="Watch Video" icon="video" cta="Learn more" href="https://learn.kodekloud.com/user/courses/linux-system-administration-for-beginners/module/ca5e9d7c-9dac-4ecc-9e21-dafef5ef2641/lesson/a06d2741-99f5-4523-b00e-f909c8ece853" />
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