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https://issues.apache.org/jira/browse/HDFS-3370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13271141#comment-13271141
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Liyin Tang commented on HDFS-3370:
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bq. Another consideration is ds quota is based on a multiple of replication
factor, so who is allowed to change the replication factor since increasing it
may impact a different user's quota?
Generally, when user creates a hardlink in Linux, it requires the EXECUTE
permission for the source directory and WRITE_EXECUTE permission for the
destination directory. And it is a well-known issue that hard links on Linux
could create local DoS vulnerability and security problems, especially when
malicious user keeps creating hard links to other users files and let others
run out of quota. One of solutions to prevent this problem is to set the
permission of the dir correctly.
HDFS hardlink should follow the same permission requirements as genreal Linux
FS and only allow the trusted users or groups have right permission to create
hardlinks. The same security principle shall apply for setReplication
operation, which can be treated as a normal write operation in general Linux FS.
Thanks Daryn Sharp so much for the above discussion.
It really helps us to re-visit several design issues and improve the solutions.
I will update the design doc later.
> HDFS hardlink
> -------------
>
> Key: HDFS-3370
> URL: https://issues.apache.org/jira/browse/HDFS-3370
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Hairong Kuang
> Assignee: Liyin Tang
>
> We'd like to add a new feature hardlink to HDFS that allows harlinked files
> to share data without copying. Currently we will support hardlinking only
> closed files, but it could be extended to unclosed files as well.
> Among many potential use cases of the feature, the following two are
> primarily used in facebook:
> 1. This provides a lightweight way for applications like hbase to create a
> snapshot;
> 2. This also allows an application like Hive to move a table to a different
> directory without breaking current running hive queries.
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