equery: add page (#920)

pages/linux/equery.md

@@ -0,0 +1,23 @@
+# equery
+
+> View information about Portage packages.
+
+- List all installed packages:
+
+`equery list '*'`
+
+- Search for installed packages in the Portage tree and in overlays:
+
+`equery list -po {{package_name}}`
+
+- List all packages that depend on a given package:
+
+`equery depends {{package_name}}`
+
+- List all packages that a given package depends on:
+
+`equery depgraph {{package_name}}`
+
+- List all files installed by a package:
+
+`equery files --tree {{package_name}}`