Database Reference
In-Depth Information
Table 10-2. Important HDFS daemon properties
Property name
Type
Default value
Description
URI
The default filesys-
tem. The URI defines
the hostname and port
that the namenode's
RPC server runs on.
The default port is
8020. This property is
set in
core-site.xml
.
fs.defaultFS
file:///
Comma-
separated
directory
names
The list of directories
where the namenode
stores its persistent
metadata. The namen-
ode stores a copy of
the metadata in each
directory in the list.
dfs.namenode.name.dir
file://${hadoop.tmp.dir}/
dfs/name
Comma-
separated
directory
names
A list of directories
where the datanode
stores blocks. Each
block is stored in only
one of these director-
ies.
dfs.datanode.data.dir
file://${hadoop.tmp.dir}/
dfs/data
dfs.namenode.checkpoint.dir
Comma-
separated
directory
names
A list of directories
where the secondary
namenode stores
checkpoints. It stores
a copy of the check-
point in each direct-
ory in the list.
file://${hadoop.tmp.dir}/
dfs/namesecondary
WARNING
Note that the storage directories for HDFS are under Hadoop's temporary directory by default (this is
configured via the
hadoop.tmp.dir
property, whose default is
/tmp/hadoop-${user.name}
).
Therefore, it is critical that these properties are set so that data is not lost by the system when it clears out
temporary directories.
