Database Reference
In-Depth Information
Check the upgrade
This shows that the upgrade is complete. At this stage, you should run some sanity checks
(step 7) on the filesystem (e.g., check files and blocks using
fsck
, test basic file opera-
tions). You might choose to put HDFS into safe mode while you are running some of
these checks (the ones that are read-only) to prevent others from making changes; see
Roll back the upgrade (optional)
If you find that the new version is not working correctly, you may choose to roll back to
the previous version (step 9). This is possible only if you have not finalized the upgrade.
WARNING
A rollback reverts the filesystem state to before the upgrade was performed, so any changes made in the
meantime will be lost. In other words, it rolls back to the previous state of the filesystem, rather than
downgrading the current state of the filesystem to a former version.
First, shut down the new daemons:
%
$NEW_HADOOP_HOME/bin/stop-dfs.sh
Then start up the old version of HDFS with the
-rollback
option:
%
$OLD_HADOOP_HOME/bin/start-dfs.sh -rollback
This command gets the namenode and datanodes to replace their current storage director-
ies with their previous copies. The filesystem will be returned to its previous state.
Finalize the upgrade (optional)
When you are happy with the new version of HDFS, you can finalize the upgrade (step 9)
to remove the previous storage directories.
WARNING
After an upgrade has been finalized, there is no way to roll back to the previous version.
This step is required before performing another upgrade:
%
$NEW_HADOOP_HOME/bin/hdfs dfsadmin -finalizeUpgrade
%
$NEW_HADOOP_HOME/bin/hdfs dfsadmin -upgradeProgress status
There are no upgrades in progress.
HDFS is now fully upgraded to the new version.
