HDFS快照

• 在data目录下启用快照

[xiaoqiu@s150 /home/xiaoqiu/hadoop_tmp]$ hdfs dfsadmin -allowSnapshot data

• 创建快照

[xiaoqiu@s150 /home/xiaoqiu/hadoop_tmp]$ hdfs dfs -createSnapshot data ss1

• 查看快照信息

[xiaoqiu@s150 /home/xiaoqiu]$ hdfs dfs -lsr  /user/xiaoqiu/data/.snapshot/ss1
lsr: DEPRECATED: Please use 'ls -R' instead.
-rw-r--r--   2 xiaoqiu supergroup          4 2017-12-29 16:08 /user/xiaoqiu/data/.snapshot/ss1/1.txt
drwxr-xr-x   - xiaoqiu supergroup          0 2017-12-29 15:57 /user/xiaoqiu/data/.snapshot/ss1/a
drwxr-xr-x   - xiaoqiu supergroup          0 2017-12-29 15:57 /user/xiaoqiu/data/.snapshot/ss1/a/b
[xiaoqiu@s150 /home/xiaoqiu]$

• web访问快照信息

• 快照并不会产生新的文件，我们可以通过查看ID

• 对HDFS的文件进行修改

[xiaoqiu@s150 /home/xiaoqiu]$ echo aaa > 2.txt
[xiaoqiu@s150 /home/xiaoqiu]$ hdfs dfs -appendToFile 2.txt data/1.txt
[xiaoqiu@s150 /home/xiaoqiu]$ hdfs dfs -cat data/1.txt
123
aaa
[xiaoqiu@s150 /home/xiaoqiu]$ hdfs dfs -cat data/.snapshot/ss1
cat: `data/.snapshot/ss1': Is a directory
[xiaoqiu@s150 /home/xiaoqiu]$ hdfs dfs -cat data/.snapshot/ss1/1.txt
123
[xiaoqiu@s150 /home/xiaoqiu]$

• 删除快照

[xiaoqiu@s150 /home/xiaoqiu]$ hdfs dfs -deleteSnapshot data ss1