Checkpoint HDFS
Perform the following steps on the NameNode host. If you are configured for NameNode HA, perform the following steps on the Active NameNode. You can locate the Active NameNode from Ambari Web > Services > HDFS in the Summary area.
Check the NameNode directory to ensure that there is no snapshot of any prior HDFS upgrade. Specifically, using Ambari Web, browse to Services > HDFS > Configs, and examine the dfs.namenode.name.dir in the NameNode Directories property. Make sure that only a
/current
directory and no/previous
directory exists on the NameNode host.Create the following log and other files. Creating these logs allows you to check the integrity of the file system after the Stack upgrade.
As the HDFS user,
"su -l [HDFS_USER]"
run the following (where [HDFS_USER] is the HDFS Service user, for example, hdfs):
Run fsck with the following flags and send the results to a log. The resulting file contains a complete block map of the file system. You use this log later to confirm the upgrade.
hdfs fsck / -files -blocks -locations > dfs-old-fsck-1.log
Create a list of all the DataNodes in the cluster.
hdfs dfsadmin -report > dfs-old-report-1.log
Optional: Capture the complete namespace of the file system. The following command does a recursive listing of the root file system:
hdfs dfs -ls -R / > dfs-old-lsr-1.log
Optional: Copy all unrecoverable data stored in HDFS to a local file system or to a backup instance of HDFS.
Save the namespace. As the HDFS user, " su -l [HDFS_USER] ", you must put the cluster in Safe Mode.
hdfs dfsadmin -safemode enter
hdfs dfsadmin -saveNamespace
Note In a highly-available NameNode configuration, the command
hdfs dfsadmin -saveNamespace
sets a checkpoint in the first NameNode specified in the configuration, in
dfs.ha.namenodes.[nameserviceID]
.You can also use the
dfsadmin -fs
option to specify which NameNode to connect. For example, to force a checkpoint in NameNode2:
hdfs dfsadmin -fs hdfs://namenode2-hostname:namenode2-port -saveNamespace
Copy the checkpoint files located in
$[dfs.namenode.name.dir]/current
into a backup directory.Note In a highly-available NameNode configuration, the location of the checkpoint depends on where the
saveNamespace
command is sent, as defined in the preceding step.
Store the layoutVersion for the NameNode located at
$[dfs.namenode.name.dir]/current/VERSION
, into a backup directory where$[dfs.namenode.name.dir]
is the value of the config parameter NameNode directories.This file will be used later to verify that the layout version is upgraded.
As the HDFS user, " su -l [HDFS_USER] ", take the NameNode out of Safe Mode.
hdfs dfsadmin -safemode leave
Next Steps