Update DTR reference titles

datacenter/dtr/2.1/reference/backup.md

@@ -1,5 +1,5 @@
 ---
-title: backup
+title: docker/dtr backup
 keywords:
 - docker, dtr, cli, backup
 description: Backup a DTR cluster to a tar file and stream it to stdout

datacenter/dtr/2.1/reference/dumpcerts.md

@@ -1,5 +1,5 @@
 ---
-title: dumpcerts
+title: docker/dtr dumpcerts
 keywords:
 - docker, dtr, cli, dumpcerts
 description: Dump out the TLS certificates used by this DTR instance

datacenter/dtr/2.1/reference/images.md

@@ -1,5 +1,5 @@
 ---
-title: images
+title: docker/dtr images
 keywords:
 - docker, dtr, cli, images
 description: Lists all the images necessary to install DTR

datacenter/dtr/2.1/reference/install.md

@@ -1,5 +1,5 @@
 ---
-title: install
+title: docker/dtr install
 keywords:
 - docker, dtr, cli, install
 description: Install Docker Trusted Registry on this Docker Engine

datacenter/dtr/2.1/reference/join.md

@@ -1,5 +1,5 @@
 ---
-title: join
+title: docker/dtr join
 keywords:
 - docker, dtr, cli, join
 description: Add a new replica to an existing DTR cluster

datacenter/dtr/2.1/reference/reconfigure.md

@@ -1,5 +1,5 @@
 ---
-title: reconfigure
+title: docker/dtr reconfigure
 keywords:
 - docker, dtr, cli, reconfigure
 description: Change DTR configurations

datacenter/dtr/2.1/reference/remove.md

@@ -1,5 +1,5 @@
 ---
-title: remove
+title: docker/dtr remove
 keywords:
 - docker, dtr, cli, remove
 description: Remove a replica from a DTR cluster

datacenter/dtr/2.1/reference/restore.md

@@ -1,5 +1,5 @@
 ---
-title: restore
+title: docker/dtr restore
 keywords:
 - docker, dtr, cli, restore
 description: Create a new DTR cluster from an existing backup

datacenter/dtr/2.1/reference/upgrade.md

@@ -1,5 +1,5 @@
 ---
-title: upgrade
+title: docker/dtr upgrade
 keywords:
 - docker, dtr, cli, upgrade
 description: Upgrade a v2.0.0 or later cluster to this version of DTR