通過NFSv3掛載HDFS到本地目錄  -- 2續hdfs-nfs閘道器解決錯誤

4.8 總結 - 主要命令列表

基本順序如下：

cd /home/hdfs/hadoop-2.7.1
sbin/stop-dfs.sh
service nfs stop
service rpcbind stop
sbin/hadoop-daemon.sh --script /home/hdfs/hadoop-2.7.1/bin/hdfs start portmap
sbin/hadoop-daemon.sh --script /home/hdfs/hadoop-2.7.1/bin/hdfs start nfs3
rpcinfo -p ip-172-30-0-129
showmount -e ip-172-30-0-129
sbin/start-dfs.sh
mount -t nfs -o vers=3,proto=tcp,nolock,noacl,sync ip-172-30-0-129:/  /mnt/hdfs

4.9 主要錯誤列表
錯誤1：
[[email protected] hadoop-2.7.1]# mount -t nfs -o vers=3,proto=tcp,nolock,noacl,sync ip-172-30-0-129:/  /mnt/hdfs
mount.nfs: mounting ip-172-30-0-129:/ failed, reason given by server: No such file or directory
沒有開啟hdfs服務


錯誤2：
[[email protected] hadoop-2.7.1]# mount -t nfs -o vers=3,proto=tcp,nolock,noacl,sync ip-172-30-0-129:/  /mnt/hdfs
mount.nfs: mount system call failed
可能portmap和nfs閘道器都成功啟動了，但是，無法連結hdfs服務，可能原因許可權，或者配置錯誤。


錯誤3：
[

[email protected] hadoop-2.7.1]# mount -t nfs -o proto=tcp,nolock,noacl,sync 172.30.0.129:/  /mnt/hdfs
mount.nfs: access denied by server while mounting 172.30.0.129:/
配置，在兩個xml檔案中，不要配置錯了。


錯誤4：
[[email protected] hadoop-2.7.1]# showmount -e 172.30.0.129
clnt_create: RPC: Program not registered


錯誤5：
如果檢查 hadoop-***-nfs3-***.log，看到類似的提示：
2016-01-23 04:27:16,788 ERROR org.apache.hadoop.hdfs.nfs.mount.RpcProgramMountd: Can't get handle for export:/
java.net.ConnectException: Call From ip-172-30-0-129/172.30.0.129 to localhost:9000 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
表明，啟動nfs閘道器的時候，應該切換到配置中設定的使用者，（非root）。


需要檢查的其他情況：
a.) selinux, 應該關閉： sestatus -v
b.) 防火牆：應確保相應的埠開啟：service iptables status
c.) nfs配置，/etc/sysconfig/nfs，檢查是否允許版本3和版本4


參考文獻：
a. http://hortonworks.com/community/forums/topic/nfs-to-hdfs-gateway-error-user-hdfs-is-not-allowed-to-impersonate-root/
b. http://stackoverflow.com/questions/25073792/error-e0902-exception-occured-user-root-is-not-allowed-to-impersonate-root
c. http://bbs.csdn.net/topics/391861078
d. http://duguyiren3476.iteye.com/blog/2209242


4.10 極簡配置
core-site.xml檔案中：
<property>
    <name>hadoop.proxyuser.nfsserver.groups</name>
    <value>*</value>
</property>
<property>
    <name>hadoop.proxyuser.nfsserver.hosts</name>
    <value>*</value>
</property>
hdfs-site.xml檔案中：
<property>
    <name>nfs.dump.dir</name>
    <value>/tmp/.hdfs-nfs</value>
</property>
<property>
    <name>nfs.rtmax</name>
    <value>1048576</value>
    <description>This is the maximum size in bytes of a READ request supported by the NFS gateway. If you change this, make sure you also update the nfs mount's rsize(add rsize= # of bytes to the mount directive).</description>
</property>
<property>
    <name>nfs.wtmax</name>
    <value>65536</value>
    <description>This is the maximum size in bytes of a WRITE request supported by the NFS gateway. If you change this, make sure you also update the nfs mount's wsize(add wsize= # of bytes to the mount directive).</description>
</property>
<property>
    <name>nfs.exports.allowed.hosts</name>
    <value>* rw</value>
    <description>允許所有主機對檔案有rw許可權</description>
</property>