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| <h1>Hadoop Archives</h1> |
| <div id="minitoc-area"> |
| <ul class="minitoc"> |
| <li> |
| <a href="#What+are+Hadoop+archives%3F"> What are Hadoop archives? </a> |
| </li> |
| <li> |
| <a href="#How+to+create+an+archive%3F"> How to create an archive? </a> |
| </li> |
| <li> |
| <a href="#How+to+look+up+files+in+archives%3F"> How to look up files in archives? </a> |
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| |
| <a name="N1000D"></a><a name="What+are+Hadoop+archives%3F"></a> |
| <h2 class="h3"> What are Hadoop archives? </h2> |
| <div class="section"> |
| <p> |
| Hadoop archives are special format archives. A Hadoop archive |
| maps to a file system directory. A Hadoop archive always has a *.har |
| extension. A Hadoop archive directory contains metadata (in the form |
| of _index and _masterindex) and data (part-*) files. The _index file contains |
| the name of the files that are part of the archive and the location |
| within the part files. |
| </p> |
| </div> |
| |
| <a name="N10017"></a><a name="How+to+create+an+archive%3F"></a> |
| <h2 class="h3"> How to create an archive? </h2> |
| <div class="section"> |
| <p> |
| |
| <span class="codefrag">Usage: hadoop archive -archiveName name <src>* <dest></span> |
| |
| </p> |
| <p> |
| -archiveName is the name of the archive you would like to create. |
| An example would be foo.har. The name should have a *.har extension. |
| The inputs are file system pathnames which work as usual with regular |
| expressions. The destination directory would contain the archive. |
| Note that this is a Map/Reduce job that creates the archives. You would |
| need a map reduce cluster to run this. The following is an example:</p> |
| <p> |
| |
| <span class="codefrag">hadoop archive -archiveName foo.har /user/hadoop/dir1 /user/hadoop/dir2 /user/zoo/</span> |
| |
| </p> |
| <p> |
| In the above example /user/hadoop/dir1 and /user/hadoop/dir2 will be |
| archived in the following file system directory -- /user/zoo/foo.har. |
| The sources are not changed or removed when an archive is created. |
| </p> |
| </div> |
| |
| <a name="N1002F"></a><a name="How+to+look+up+files+in+archives%3F"></a> |
| <h2 class="h3"> How to look up files in archives? </h2> |
| <div class="section"> |
| <p> |
| The archive exposes itself as a file system layer. So all the fs shell |
| commands in the archives work but with a different URI. Also, note that |
| archives are immutable. So, rename's, deletes and creates return |
| an error. URI for Hadoop Archives is |
| </p> |
| <p> |
| <span class="codefrag">har://scheme-hostname:port/archivepath/fileinarchive</span> |
| </p> |
| <p> |
| If no scheme is provided it assumes the underlying filesystem. |
| In that case the URI would look like |
| </p> |
| <p> |
| <span class="codefrag"> |
| har:///archivepath/fileinarchive</span> |
| </p> |
| <p> |
| Here is an example of archive. The input to the archives is /dir. The directory dir contains |
| files filea, fileb. To archive /dir to /user/hadoop/foo.har, the command is |
| </p> |
| <p> |
| <span class="codefrag">hadoop archive -archiveName foo.har /dir /user/hadoop</span> |
| |
| </p> |
| <p> |
| To get file listing for files in the created archive |
| </p> |
| <p> |
| <span class="codefrag">hadoop dfs -lsr har:///user/hadoop/foo.har</span> |
| </p> |
| <p>To cat filea in archive - |
| </p> |
| <p> |
| <span class="codefrag">hadoop dfs -cat har:///user/hadoop/foo.har/dir/filea</span> |
| </p> |
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