hadoop启动时，报ssh: Could not resolve hostname xxx: Name or service not known

问题：hadoop启动时，报ssh: Could not resolve hostname xxx: Name or service not known

错误信息：
	[root@master hadoop-2.2.0]# sbin/start-dfs.sh 
	17/08/06 13:08:59 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
	Starting namenodes on [Java HotSpot(TM) 64-Bit Server VM warning: You have loaded library /data/cloud/hadoop/hadoop-2.2.0/lib/native/libhadoop.so.1.0.0 which might have disabled stack guard. The VM will try to fix the stack guard now.
	It's highly recommended that you fix the library with 'execstack -c ', or link it with '-z noexecstack'.
	master]
	sed: -e expression #1, char 6: unknown option to `s'
	library: ssh: Could not resolve hostname library: Name or service not known
	loaded: ssh: Could not resolve hostname loaded: Name or service not known
	VM: ssh: Could not resolve hostname VM: Name or service not known
	have: ssh: Could not resolve hostname have: Name or service not known
	Server: ssh: Could not resolve hostname Server: Name or service not known
	64-Bit: ssh: Could not resolve hostname 64-Bit: Name or service not known
	have: ssh: Could not resolve hostname have: Name or service not known
	disabled: ssh: Could not resolve hostname disabled: Name or service not known
	VM: ssh: Could not resolve hostname VM: Name or service not known
	to: ssh: Could not resolve hostname to: No address associated with hostname
	Java: ssh: Could not resolve hostname Java: No address associated with hostname
	which: ssh: Could not resolve hostname which: Name or service not known
	will: ssh: Could not resolve hostname will: Name or service not known
	might: ssh: Could not resolve hostname might: Name or service not known
	stack: ssh: Could not resolve hostname stack: Name or service not known
	The: ssh: Could not resolve hostname The: Name or service not known
	stack: ssh: Could not resolve hostname stack: Name or service not known
	guard.: ssh: Could not resolve hostname guard.: Name or service not known
	recommended: ssh: Could not resolve hostname recommended: Name or service not known
	guard: ssh: Could not resolve hostname guard: Name or service not known
	try: ssh: Could not resolve hostname try: Name or service not known
	fix: ssh: Could not resolve hostname fix: Name or service not known
	-c: Unknown cipher type 'cd'
	fix: ssh: Could not resolve hostname fix: Name or service not known
	the: ssh: Could not resolve hostname the: Name or service not known
	the: ssh: Could not resolve hostname the: Name or service not known
	with: ssh: Could not resolve hostname with: Name or service not known
	it: ssh: Could not resolve hostname it: No address associated with hostname
	with: ssh: Could not resolve hostname with: Name or service not known
	or: ssh: Could not resolve hostname or: Name or service not known
	The authenticity of host 'master (192.168.1.110)' can't be established.
	RSA key fingerprint is db:8e:ce:15:18:ad:9d:16:0e:88:98:0d:da:06:e4:18.
	Are you sure you want to continue connecting (yes/no)? that: ssh: Could not resolve hostname that: Name or service not known
	highly: ssh: Could not resolve hostname highly: Name or service not known
	library: ssh: Could not resolve hostname library: Name or service not known
	now.: ssh: Could not resolve hostname now.: No address associated with hostname
	You: ssh: Could not resolve hostname You: No address associated with hostname
	you: ssh: Could not resolve hostname you: No address associated with hostname
	link: ssh: Could not resolve hostname link: No address associated with hostname
	HotSpot(TM): ssh: Could not resolve hostname HotSpot(TM): Temporary failure in name resolution
	warning:: ssh: Could not resolve hostname warning:: Temporary failure in name resolution
	It's: ssh: Could not resolve hostname It's: Temporary failure in name resolution
	',: ssh: Could not resolve hostname ',: Temporary failure in name resolution
	'execstack: ssh: Could not resolve hostname 'execstack: Temporary failure in name resolution
	'-z: ssh: Could not resolve hostname '-z: Temporary failure in name resolution
	noexecstack'.: ssh: Could not resolve hostname noexecstack'.: Temporary failure in name resolution

解决方法：
	在/etc/profile文件中添加：
		export HADOOP_COMMON_LIB_NATIVE_DIR=$HADOOP_HOME/lib/native
		export HADOOP_OPTS=-Djava.library.path=$HADOOP_HOME/lib
		
	注意：是export HADOOP_OPTS=-Djava.library.path=$HADOOP_HOME/lib，而不是export HADOOP_OPTS="-Djava.library.path=$HADOOP_HOME/lib"