Add the nix-env for common

pages/common/nix-env.md

@@ -0,0 +1,39 @@
+# nix-env
+
+> Manipulate or query Nix user environments
+
+- Show available package with name or without name
+
+`nix-env -qa {{pkg_name}}`
+
+- Show the status of available packages
+
+`nix-env -qas`                             
+
+- Install package
+
+`nix-env -i {{pkg_name}}`
+
+- Uninstall package
+
+`nix-env -e {{pkg_name}}`
+
+- Upgrade one package
+
+`nix-env -u {{pkg_name}}`
+
+- Upgrade all packages
+
+`nix-env -u`
+
+- Rollback changes
+    
+`nix-env --rollback`
+
+- List all profiles
+
+`nix-env --list-generations`
+
+- Switch to specific profile
+
+`nix-env --switch-generation {{profile_number}}`