kawamon

hdfs dfsadmin -allowSnapshot contents
Allowing snapshot on contents succeeded
hdfs lsSnapshottableDir
drwxr-xr-x 0 training supergroup 0 2020-06-12 01:23 0 65536 /user/training/contents
hdfs dfs -createSnapshot /user/training/contents snapshotv1
Created snapshot /user/training/contents/.snapshot/snapshotv1
hdfs dfs -ls /user/training/contents/.snapshot/
Found 1 items
drwxr-xr-x   - training supergroup          0 2020-06-12 01:23 /user/training/contents/.snapshot/snapshotv1
hdfs dfs -ls /user/training/contents/.snapshot/snapshotv1/

kawamon

## Hadoop 3.1.1. (CDP7.1.1)
$ hdfs dfsadmin
Usage: hdfs dfsadmin
Note: Administrative commands can only be run as the HDFS superuser.
	[-report [-live] [-dead] [-decommissioning] [-enteringmaintenance] [-inmaintenance]]
	[-safemode <enter | leave | get | wait>]
	[-saveNamespace [-beforeShutdown]]
	[-rollEdits]
	[-restoreFailedStorage true|false|check]
	[-refreshNodes]

kawamon

********************
test start
********************
mkdir/rmdir
********************
hdfs dfs -mkdir /tmp/testdir
hdfs dfs -mkdir -p /tmp/subdir1/subdir2/subdir3
hdfs dfs -mkdir testdirhome
hdfs dfs -ls /tmp
Found 7 items

kawamon

{
   "hostName": "datanode-100",
   "Port": 50010,
   "adminState": "NORMAL"
}
...

kawamon

namenode-host# echo $((`date +%s` * 1000 + 60 * 60 * 1000))
1492543534000
namenode-host# cat /etc/hadoop/conf/maintenance
{
   "hostName": "datanode-100",
   "Port": 50010,
   "adminState": "IN_MAINTENANCE",
   "maintenanceExpireTimeInMS": 1492543534000
}
{

kawamon

<property>
   <name>dfs.hosts</name>
   <value>/etc/hadoop/conf/maintenance</value>
</property>

kawamon

<property>
 <name>dfs.namenode.hosts.provider.classname</name>
 <value>org.apache.hadoop.hdfs.server.blockmanagement.CombinedHostFileManager
  </value>
</property>

kawamon

<property>
   <name>dfs.namenode.maintenance.replication.min</name>
   <value>1</value>
</property>

kawamon

{
   "hostName": <DataNode hostname>,
   "Port": <DataNode port>,
   "upgradeDomain": <upgrade domain>,
   "adminState": <DataNode admin state>,
   "maintenanceExpireTimeInMS": <timeout in epoch millis>
}

kawamon

# df -h
Filesystem      Size  Used Avail Use% Mounted on
….
/var/disk1      5.8G  2.1G  3.5G  37% /mnt/disk1
/var/disk2      5.8G  1.6G  4.0G  29% /mnt/disk2