Install td-agent2 and faced the following problem at startup

• version: td-agent2 (td-agent-2.3.1-0.el6.x86_64)
• OS: centos 6.8
• Configuration (/etc/td-agent/td-agent.conf)

<source>
  @type unix
  path  /var/run/td-agent/td-agent.sock
</source>

• fluent startup log

2016-06-02 12:51:53 +0900 [error]: config error file="/etc/td-agent/td-agent.conf" error="Unknown input plugin 'unix'. Run 'gem search -rd fluent-plugin' to find plugins"

• step

1. Install td-agent with "install-redhat-td-agent2.sh"
2. Wrote "/etc/td-agent/td-agent.conf"
3. Update all gems "td-agent-gem update"
4. Start process "service td-agent start"