linux - ElasticSearch如何知道在线可以安装哪些Plugin?下载安装又应该去哪里下载？

环境

# uname -r
3.10.0-514.el7.x86_64
# curl -XGET 'http://node1:9200/'
{
  "name" : "node1",
  "cluster_name" : "chen_es",
  "cluster_uuid" : "ThlwIW7zTL6byQNcmp73Rg",
  "version" : {
    "number" : "5.1.1",
    "build_hash" : "5395e21",
    "build_date" : "2016-12-06T12:36:15.409Z",
    "build_snapshot" : false,
    "lucene_version" : "6.3.0"
  },
  "tagline" : "You Know, for Search"
}
# curl -XGET 'http://node1:9200/_cluster/health?pretty'
{
  "cluster_name" : "chen_es",
  "status" : "green",
  "timed_out" : false,
  "number_of_nodes" : 3,
  "number_of_data_nodes" : 3,
  "active_primary_shards" : 0,
  "active_shards" : 0,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 0,
  "delayed_unassigned_shards" : 0,
  "number_of_pending_tasks" : 0,
  "number_of_in_flight_fetch" : 0,
  "task_max_waiting_in_queue_millis" : 0,
  "active_shards_percent_as_number" : 100.0
}

使用elasticsearch-plugin命令安装 plugin总是提示未知的 plugin

# /usr/share/elasticsearch/bin/elasticsearch-plugin install mobz/elasticsearch-head
A tool for managing installed elasticsearch plugins

Commands
--------
list - Lists installed elasticsearch plugins
install - Install a plugin
remove - Removes a plugin from elasticsearch

Non-option arguments:
command

Option         Description
------         -----------
-h, --help     show help
-s, --silent   show minimal output
-v, --verbose  show verbose output
ERROR: Unknown plugin mobz/elasticsearch-head

下面几条命令也是这样

/usr/share/elasticsearch/bin/elasticsearch-plugin install elacsticsearch-bigdesk
/usr/share/elasticsearch/bin/elasticsearch-plugin install elasticsearch-head
/usr/share/elasticsearch/bin/elasticsearch-plugin install mobz/elasticsearch-head

我粗略的看了一下 plugin的文档，也 Baidu 了一圈。没找到答案

问题很简单。怎么知道在线有哪些 plugin?
下载安装的话，去哪里下载？是否只能像elasticsearch-head这样，只能一个一个去各大开源站点或者个人网站上面去找？