dnf-system-upgrade: add page (#22487)

pages/linux/dnf-system-upgrade.md

@@ -0,0 +1,28 @@
+# dnf system-upgrade
+
+> Upgrade Fedora to a new major release.
+> More information: <https://dnf5.readthedocs.io/en/latest/commands/system-upgrade.8.html>.
+
+- Prepare the system by upgrading all installed packages:
+
+`sudo dnf upgrade --refresh`
+
+- Download packages required for the new release version:
+
+`sudo dnf system-upgrade download --releasever {{release_version}}`
+
+- Reboot and start the upgrade process:
+
+`sudo dnf system-upgrade reboot`
+
+- Display the status of the current upgrade transaction:
+
+`sudo dnf system-upgrade status`
+
+- Display logs from previous upgrade attempts:
+
+`sudo dnf system-upgrade log`
+
+- Remove cached upgrade data and packages:
+
+`sudo dnf system-upgrade clean`