docs: remove some references to obsolete docker versions

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/extend/index.md

@@ -21,8 +21,8 @@ keywords: "API, Usage, plugins, documentation, developer"
 Docker Engine's plugin system allows you to install, start, stop, and remove
 plugins using Docker Engine.
 
-For information about the legacy plugin system available in Docker Engine 1.12
-and earlier, see [Understand legacy Docker Engine plugins](legacy_plugins.md).
+For information about legacy (non-managed) plugins, refer to
+[Understand legacy Docker Engine plugins](legacy_plugins.md).
 
 > **Note**
 >

docs/reference/builder.md

@@ -2216,8 +2216,6 @@ are stored currently).
 When the health status of a container changes, a `health_status` event is
 generated with the new status.
 
-The `HEALTHCHECK` feature was added in Docker 1.12.
-
 
 ## SHELL
 
@@ -2342,8 +2340,6 @@ environment variable expansion semantics could be modified.
 The `SHELL` instruction can also be used on Linux should an alternate shell be
 required such as `zsh`, `csh`, `tcsh` and others.
 
-The `SHELL` feature was added in Docker 1.12.
-
 ## External implementation features
 
 This feature is only available when using the  [BuildKit](#buildkit) backend.

docs/reference/commandline/build.md

@@ -715,10 +715,9 @@ experimental flag enabled.
 
 #### Enable Docker experimental
 
-Experimental features are now included in the standard Docker binaries as of
-version 1.13.0. For enabling experimental features, you need to start the
-Docker daemon with `--experimental` flag. You can also enable the daemon flag
-via `/etc/docker/daemon.json`. e.g.
+To enable experimental features, you need to start the Docker daemon with
+`--experimental` flag. You can also enable the daemon flag via
+`/etc/docker/daemon.json`, for example:
 
 ```json
 {

docs/reference/commandline/dockerd.md

@@ -205,8 +205,7 @@ The Docker client will honor the `HTTP_PROXY`, `HTTPS_PROXY`, and `NO_PROXY`
 environment variables (or the lowercase versions thereof). `HTTPS_PROXY` takes
 precedence over `HTTP_PROXY`.
 
-Starting with Docker 18.09, the Docker client supports connecting to a remote
-daemon via SSH:
+The Docker client supports connecting to a remote daemon via SSH:
 
 ```
 $ docker -H ssh://me@example.com:22 ps
@@ -219,17 +218,17 @@ remote host with public key authentication. Password authentication is not
 supported. If your key is protected with passphrase, you need to set up
 `ssh-agent`.
 
-Also, you need to have `docker` binary 18.09 or later on the daemon host.
-
 #### Bind Docker to another host/port or a Unix socket
 
-> **Warning**:
+> **Warning**
+>
 > Changing the default `docker` daemon binding to a
 > TCP port or Unix *docker* user group will increase your security risks
 > by allowing non-root users to gain *root* access on the host. Make sure
 > you control access to `docker`. If you are binding
 > to a TCP port, anyone with access to that port has full Docker access;
 > so it is not advisable on an open network.
+{: .warning :}
 
 With `-H` it is possible to make the Docker daemon to listen on a
 specific IP and port. By default, it will listen on
@@ -1110,13 +1109,10 @@ system's list of trusted CAs instead of enabling `--insecure-registry`.
 
 #### Legacy Registries
 
-Starting with Docker 17.12, operations against registries supporting only the
-legacy v1 protocol are no longer supported. 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.
-
-The `disable-legacy-registry` configuration option has been removed and, when
-used, will produce an error on daemon startup.
+Operations against registries supporting only the legacy v1 protocol are no longer
+supported. 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.
 
 
 ### Running a Docker daemon behind an HTTPS_PROXY

docs/reference/commandline/export.md

@@ -23,7 +23,7 @@ with the container. If a volume is mounted on top of an existing directory in
 the container, `docker export` will export the contents of the *underlying*
 directory, not the contents of the volume.
 
-Refer to [Backup, restore, or migrate data volumes](https://docs.docker.com/v17.03/engine/tutorials/dockervolumes/#backup-restore-or-migrate-data-volumes)
+Refer to [Backup, restore, or migrate data volumes](https://docs.docker.com/storage/volumes/#backup-restore-or-migrate-data-volumes)
 in the user guide for examples on exporting data in a volume.
 
 ## Examples

docs/reference/commandline/system_prune.md

@@ -97,15 +97,6 @@ deleted: sha256:3a88a5c81eb5c283e72db2dbc6d65cbfd8e80b6c89bb6e714cfaaa0eed99c548
 Total reclaimed space: 13.5 MB
 ```
 
-> **Note**
->
-> The `--volumes` option was added in Docker 17.06.1. Older versions of Docker
-> prune volumes by default, along with other Docker objects. On older versions,
-> run `docker container prune`, `docker network prune`, and `docker image prune`
-> separately to remove unused containers, networks, and images, without removing
-> volumes.
-
-
 ### Filtering
 
 The filtering flag (`--filter`) format is of "key=value". If there is more

docs/reference/run.md

@@ -1396,10 +1396,7 @@ drwxrwxr-x 1 1000 1000   4096 Dec  4 06:11 .git
 ```
 
 The default seccomp profile will adjust to the selected capabilities, in order to allow
-use of facilities allowed by the capabilities, so you should not have to adjust this,
-since Docker 1.12. In Docker 1.10 and 1.11 this did not happen and it may be necessary
-to use a custom seccomp profile or use `--security-opt seccomp=unconfined` when adding
-capabilities.
+use of facilities allowed by the capabilities, so you should not have to adjust this.
 
 ## Logging drivers (--log-driver)