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226<h1>Archives Guide</h1>
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229<li>
230<a href="#What+are+Hadoop+archives%3F"> What are Hadoop archives? </a>
231</li>
232<li>
233<a href="#How+to+create+an+archive%3F"> How to create an archive? </a>
234</li>
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236<a href="#How+to+look+up+files+in+archives%3F"> How to look up files in archives? </a>
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240       
241<a name="N1000D"></a><a name="What+are+Hadoop+archives%3F"></a>
242<h2 class="h3"> What are Hadoop archives? </h2>
243<div class="section">
244<p>
245        Hadoop archives are special format archives. A Hadoop archive
246        maps to a file system directory. A Hadoop archive always has a *.har
247        extension. A Hadoop archive directory contains metadata (in the form
248        of _index and _masterindex) and data (part-*) files. The _index file contains
249        the name of the files that are part of the archive and the location
250        within the part files.
251        </p>
252</div>
253       
254<a name="N10017"></a><a name="How+to+create+an+archive%3F"></a>
255<h2 class="h3"> How to create an archive? </h2>
256<div class="section">
257<p>
258       
259<span class="codefrag">Usage: hadoop archive -archiveName name &lt;src&gt;* &lt;dest&gt;</span>
260       
261</p>
262<p>
263        -archiveName is the name of the archive you would like to create.
264        An example would be foo.har. The name should have a *.har extension.
265        The inputs are file system pathnames which work as usual with regular
266        expressions. The destination directory would contain the archive.
267        Note that this is a Map/Reduce job that creates the archives. You would
268        need a map reduce cluster to run this. The following is an example:</p>
269<p>
270       
271<span class="codefrag">hadoop archive -archiveName foo.har /user/hadoop/dir1 /user/hadoop/dir2 /user/zoo/</span>
272       
273</p>
274<p>
275        In the above example /user/hadoop/dir1 and /user/hadoop/dir2 will be
276        archived in the following file system directory -- /user/zoo/foo.har.
277        The sources are not changed or removed when an archive is created.
278        </p>
279</div>
280       
281<a name="N1002F"></a><a name="How+to+look+up+files+in+archives%3F"></a>
282<h2 class="h3"> How to look up files in archives? </h2>
283<div class="section">
284<p>
285        The archive exposes itself as a file system layer. So all the fs shell
286        commands in the archives work but with a different URI. Also, note that
287        archives are immutable. So, rename's, deletes and creates return
288        an error. URI for Hadoop Archives is
289        </p>
290<p>
291<span class="codefrag">har://scheme-hostname:port/archivepath/fileinarchive</span>
292</p>
293<p>
294        If no scheme is provided it assumes the underlying filesystem.
295        In that case the URI would look like
296        </p>
297<p>
298<span class="codefrag">
299        har:///archivepath/fileinarchive</span>
300</p>
301<p>
302        Here is an example of archive. The input to the archives is /dir. The directory dir contains
303        files filea, fileb. To archive /dir to /user/hadoop/foo.har, the command is
304        </p>
305<p>
306<span class="codefrag">hadoop archive -archiveName foo.har /dir /user/hadoop</span>
307       
308</p>
309<p>
310        To get file listing for files in the created archive
311        </p>
312<p>
313<span class="codefrag">hadoop dfs -lsr har:///user/hadoop/foo.har</span>
314</p>
315<p>To cat filea in archive -
316        </p>
317<p>
318<span class="codefrag">hadoop dfs -cat har:///user/hadoop/foo.har/dir/filea</span>
319</p>
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