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https://issues.apache.org/jira/browse/HDFS-6502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14029322#comment-14029322
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Yongjun Zhang commented on HDFS-6502:
-------------------------------------
HI [~ajisakaa],
I reviewed it and suggest a little more modification:
Original
{quote}
-update` | Overwrite if src size different from dst size | As noted in the
preceding, this is not a "sync" operation. The only criterion examined is the
source and destination file sizes; if they differ, the source file replaces the
destination file. As discussed in the Usage documentation, it also changes the
semantics for generating destination paths, so users should use this carefully.
{quote}
Current patched version
{quote}
`-update` | Overwrite if source and destination have different contents | As
noted in the preceding, this is not a "sync" operation. The criteria examined
are the source and destination file sizes, blocksizes, and checksums; if they
differ, the source file replaces the destination file. As discussed in the
Usage documentation, it also changes the semantics for generating destination
paths, so users should use this carefully.
{quote}
New suggested change:
{quote}
`-update` | Overwrite if source and destination differ in size, blocksize, or
checksum | As noted in the preceding, this is not a "sync" operation. The
criteria examined are the source and destination file sizes, blocksizes, and
checksums; if they differ, the source file replaces the destination file. As
discussed in the Usage documentation, it also changes the semantics for
generating destination paths, so users should use this carefully.
{quote}
Thanks again for the patch.
> incorrect description in distcp2 document
> -----------------------------------------
>
> Key: HDFS-6502
> URL: https://issues.apache.org/jira/browse/HDFS-6502
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: documentation
> Affects Versions: 1.2.1, 2.5.0
> Reporter: Yongjun Zhang
> Assignee: Akira AJISAKA
> Labels: newbie
> Attachments: HDFS-6502.patch
>
>
> In http://hadoop.apache.org/docs/r1.2.1/distcp2.html#UpdateAndOverwrite
> The first statement of the "Update and Overwrite" section says:
> {quote}
> -update is used to copy files from source that don't exist at the target, or
> have different contents. -overwrite overwrites target-files even if they
> exist at the source, or have the same contents.
> {quote}
> The "Command Line Options" table says :
> {quote}
> -overwrite: Overwrite destination
> -update: Overwrite if src size different from dst size
> {quote}
> Based on the implementation, making the following modification would be more
> accurate:
> The first statement of the "Update and Overwrite" section:
> {code}
> -update is used to copy files from source that don't exist at the target, or
> have different contents. -overwrite overwrites target-files if they exist at
> the target.
> {code}
> The "Command Line Options" table:
> {code}
> -overwrite: Overwrite destination
> -update: Overwrite destination if source and destination have different
> contents
> {code}
> Thanks.
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