Add system update-check example

Add an example of online checking for updates
```
set system update-check auto-check
set system update-check url <url>
```

(cherry picked from commit fd3073eef7bcbd64112e0581ba10afb58100b30d)

1 files changed, 37 insertions, 0 deletions

diff --git a/docs/configuration/system/updates.rst b/docs/configuration/system/updates.rst
new file mode 100644
index 00000000..a55bfa9a
--- /dev/null
+++ b/docs/configuration/system/updates.rst
@@ -0,0 +1,37 @@
+#######
+Updates
+#######
+
+VyOS supports online checking for updates
+
+Configuration
+=============
+
+.. cfgcmd:: set system update-check auto-check
+
+   Configure auto-checking for new images
+
+
+.. cfgcmd:: set system update-check url <url>
+
+   Configure a URL that contains information about images.
+
+
+Example
+=======
+
+.. code-block:: none
+
+  set system update-check auto-check
+  set system update-check url 'https://raw.githubusercontent.com/vyos/vyos-rolling-nightly-builds/main/version.json'
+
+Check:
+
+.. code-block:: none
+
+  vyos@r4:~$ show system updates 
+  Current version: 1.5-rolling-202312220023
+
+  Update available: 1.5-rolling-202312250024
+  Update URL: https://github.com/vyos/vyos-rolling-nightly-builds/releases/download/1.5-rolling-202312250024/1.5-rolling-202312250024-amd64.iso
+  vyos@r4:~$