synopkg: add page (#6264)

pages/linux/synopkg.md

@@ -0,0 +1,36 @@
+# synopkg
+
+> Package management utility for Synology DiskStation Manager.
+> More information: <https://www.synology.com/dsm>.
+
+- List the names of installed packages:
+
+`synopkg list --name`
+
+- List packages which depend on a specific package:
+
+`synopkg list --depend-on {{package}}`
+
+- Start/Stop a package:
+
+`sudo synopkg {{start|stop}} {{package}}`
+
+- Print the status of a package:
+
+`synopkg status {{package}}`
+
+- Uninstall a package:
+
+`sudo synopkg uninstall {{package}}`
+
+- Check if updates are available for a package:
+
+`synopkg checkupdate {{package}}`
+
+- Upgrade all packages to the latest version:
+
+`sudo synopkg upgradeall`
+
+- Install a package from a synopkg file:
+
+`sudo synopkg install {{path/to/package.spk}}`