问题描述

在Ubuntu下启动hadoop的hdfs时出现：

hadoop@ubuntu:~/hadoop-$ sbin/start-dfs.sh 
Starting namenodes on [localhost]
localhost: ssh: connect to host localhost port : Connection refused
localhost: ssh: connect to host localhost port : Connection refused
...

检查是否安装 openssh-server

$ ps -e | grep ssh
$

没有出现任何进程，则用apt-get安装 openssh-server，出现以下提示：

hadoop@ubuntu:~/hadoop-$ sudo apt-get install openssh-server
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 openssh-server : Depends: openssh-client (= :p2-)
                  Depends: openssh-sftp-server but it is not going to be installed
                  Recommends: ssh-import-id but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

手动安装 openssh-client

根据提示，到 launchpad 下载：
https://launchpad.net/ubuntu/+source/openssh/1:7.2p2-4/+build/9584683

# 手动安装下载好的deb
$ sudo dpkg -i openssh-client_7.p2-_amd64.deb

安装openssh-server

# 安装openssh-server
$ sudo apt-get install openssh-server

测试是否安装成功

$ ssh localhost