Update docs, completion scripts for disable-legacy-registry

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 2b8f0eef7338f37104464154ba65aef7db3b9703)
Signed-off-by: Andrew Hsu <andrewhsu@docker.com>
diff --git a/contrib/completion/zsh/_docker b/contrib/completion/zsh/_docker
index 0860907..4b0c1e2 100644
--- a/contrib/completion/zsh/_docker
+++ b/contrib/completion/zsh/_docker
@@ -2620,7 +2620,7 @@
                 "($help)--default-gateway-v6[Container default gateway IPv6 address]:IPv6 address: " \
                 "($help)--default-shm-size=[Default shm size for containers]:size:" \
                 "($help)*--default-ulimit=[Default ulimits for containers]:ulimit: " \
-                "($help)--disable-legacy-registry[Disable contacting legacy registries]" \
+                "($help)--disable-legacy-registry[Disable contacting legacy registries (default true)]" \
                 "($help)*--dns=[DNS server to use]:DNS: " \
                 "($help)*--dns-opt=[DNS options to use]:DNS option: " \
                 "($help)*--dns-search=[DNS search domains to use]:DNS search: " \
diff --git a/docs/deprecated.md b/docs/deprecated.md
index e1e7e12..9905994 100644
--- a/docs/deprecated.md
+++ b/docs/deprecated.md
@@ -292,7 +292,7 @@
 
 **Target For Removal In Release: v17.12**
 
-Version 1.9 adds a flag (`--disable-legacy-registry=false`) which prevents the
+Version 1.8.3 added a flag (`--disable-legacy-registry=false`) which prevents the
 docker daemon from `pull`, `push`, and `login` operations against v1
 registries.  Though enabled by default, this signals the intent to deprecate
 the v1 protocol.
diff --git a/docs/reference/commandline/dockerd.md b/docs/reference/commandline/dockerd.md
index 93774c8..ef6bcd3 100644
--- a/docs/reference/commandline/dockerd.md
+++ b/docs/reference/commandline/dockerd.md
@@ -42,7 +42,7 @@
       --default-gateway-v6 ip                 Container default gateway IPv6 address
       --default-runtime string                Default OCI runtime for containers (default "runc")
       --default-ulimit ulimit                 Default ulimits for containers (default [])
-      --disable-legacy-registry               Disable contacting legacy registries
+      --disable-legacy-registry               Disable contacting legacy registries (default true)
       --dns list                              DNS server to use (default [])
       --dns-opt list                          DNS options to use (default [])
       --dns-search list                       DNS search domains to use (default [])
@@ -901,7 +901,18 @@
 
 ##### Legacy Registries
 
-Enabling `--disable-legacy-registry` forces a docker daemon to only interact with registries which support the V2 protocol.  Specifically, the daemon will not attempt `push`, `pull` and `login` to v1 registries.  The exception to this is `search` which can still be performed on v1 registries.
+Operations against registries supporting only the legacy v1 protocol are
+disabled by default. Specifically, the daemon will not attempt `push`,
+`pull` and `login` to v1 registries. The exception to this is `search`
+which can still be performed on v1 registries.
+
+Add `"disable-legacy-registry":false` to the [daemon configuration
+file](#daemon-configuration-file), or set the
+`--disable-legacy-registry=false` flag, if you need to interact with
+registries that have not yet migrated to the v2 protocol.
+
+Interaction v1 registries will no longer be supported in Docker v17.12,
+and the `disable-legacy-registry` configuration option will be removed.
 
 #### Running a Docker daemon behind an HTTPS_PROXY
 
diff --git a/man/dockerd.8.md b/man/dockerd.8.md
index a4e0790..e9d7e68 100644
--- a/man/dockerd.8.md
+++ b/man/dockerd.8.md
@@ -192,7 +192,7 @@
   Default ulimits for containers.
 
 **--disable-legacy-registry**=*true*|*false*
-  Disable contacting legacy registries
+  Disable contacting legacy registries. Default is `true`.
 
 **--dns**=""
   Force Docker to use specific DNS servers