hdfs getconf is utility for getting configuration information from the config file.Not only for HDFS, but also actual configuration values for Yarn, core-site etc..

More commands about hdfs, see hadoop hdfs command reference

Here are some hdfs getconf command examples:

Get list of name nodes in the cluster

$ hdfs getconf -namenodes
<namenode>

Get list of secondary namenodes in the cluster

$ hdfs getconf -secondaryNameNodes
0.0.0.0

Get list of backup nodes in the cluster

$ hdfs getconf -backupNodes
0.0.0.0

Get include file path that defines the datanodes that can join the cluster

$ hdfs getconf -includeFile
Configuration dfs.hosts is missing

Get exclude file path that defines the datanodes that need to be excluded

Gets the namenode rpc addresses

$ hdfs getconf -nnRpcAddresses
<namenode>:9000

Gets a specific key from the configuration

This command is very interesting and you can use it to debug your system see what actual variable is set to your running cluster.

dfs.namenode.name.dir

$ hdfs getconf -confKey dfs.namenode.name.dir
file:///disk/c0t1,/disk/c1t1

fs.defaultFS

$ hdfs getconf -confKey fs.defaultFS
hdfs://zpool02:9000

yarn.resourcemanager.address

$ hdfs getconf -confKey yarn.resourcemanager.address
0.0.0.0:8032

mapreduce.framework.name

$ hdfs getconf -confKey mapreduce.framework.name
yarn

dfs.namenode.name.dir

$ hdfs getconf -confKey dfs.namenode.name.dir
file:///disk/c0t1,/disk/c1t1

dfs.default.chunk.view.size

$ hdfs getconf -confKey dfs.default.chunk.view.size
32768

dfs.namenode.fs-limits.max-blocks-per-file

$ hdfs getconf -confKey dfs.namenode.fs-limits.max-blocks-per-file
1048576

dfs.permissions.enabled

$ hdfs getconf -confKey dfs.permissions.enabled
true

dfs.namenode.acls.enabled

$ hdfs getconf -confKey dfs.namenode.acls.enabled
false

dfs.replication

$ hdfs getconf -confKey dfs.replication
2

dfs.replication.max

$ hdfs getconf -confKey dfs.replication.max
512

dfs.namenode.replication.min

$ hdfs getconf -confKey dfs.namenode.replication.min
1

dfs.blocksize

$ hdfs getconf -confKey dfs.blocksize
134217728

dfs.client.block.write.retries


$ hdfs getconf -confKey dfs.client.block.write.retries
3

dfs.hosts.exclude

$ hdfs getconf -confKey dfs.hosts.exclude
/opt/hadoop/hadoop-2.7.3/etc/hadoop/dfs.exclude

dfs.namenode.checkpoint.edits.dir

$ hdfs getconf -confKey dfs.namenode.checkpoint.edits.dir
file:///tmp/hadoop-hadoop/dfs/namesecondary

dfs.image.compress

$ hdfs getconf -confKey dfs.image.compress
false

dfs.image.compression.codec

$ hdfs getconf -confKey dfs.image.compression.codec
org.apache.hadoop.io.compress.DefaultCodec

dfs.user.home.dir.prefix

$ hdfs getconf -confKey dfs.user.home.dir.prefix
/user

As mentioned in the begging of this article, hdfs getconf -conKey can also get values from core.xml, yarn etc..

dfs.permissions.enabled

$ hdfs getconf -confKey dfs.permissions.enabled
true

io.file.buffer.size

$ hdfs getconf -confKey io.file.buffer.size
4096

io.bytes-per-checksum

$ hdfs getconf -confKey io.bytes-per-checksum
512

io.seqfile.local.dir

$ hdfs getconf -confKey io.seqfile.local.dir
/tmp/hadoop-hadoop/io/local

Want check more actual running variables? check the list of configurable variables in the following links then run hdfs getconf -confKey <key>

http://hadoop.apache.org/docs/r2.7.3/hadoop-project-dist/hadoop-common/core-default.xml

http://hadoop.apache.org/docs/r2.7.3/hadoop-project-dist/hadoop-hdfs/hdfs-default.xml

http://hadoop.apache.org/docs/r2.7.3/hadoop-mapreduce-client/hadoop-mapreduce-client-core/mapred-default.xml

http://hadoop.apache.org/docs/r2.7.3/hadoop-yarn/hadoop-yarn-common/yarn-default.xml