Linux System Administration for Beginners
Operation of Running Systems
Update software to provide required functionality and security
Keeping your Linux system up to date is critical—most online attacks exploit known vulnerabilities in outdated software.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.
Note
Regular updates not only patch security holes but also introduce new features and performance improvements.
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:
dnf check-update
Sample output:
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:
sudo dnf upgrade
You’ll receive a transaction summary like this:
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.
Warning
Pay attention to the download size and package count. Large upgrades on production servers may require scheduled maintenance windows.
Reboot After Core Updates
Upgrading the kernel, system services, or libraries often requires a reboot. To apply these changes, reboot the system:
sudo reboot
Note
Always verify critical services after rebooting to ensure they’ve started correctly.
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
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