31 lines
1.5 KiB
Text
31 lines
1.5 KiB
Text
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Suppose you're running low on disk space. You need to free some
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up, by finding something that's a waste of space and deleting it
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(or moving it to an archive medium). How do you find the right
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stuff to delete, that saves you the maximum space at the cost of
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minimum inconvenience?
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Unix provides the standard du utility, which scans your disk and
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tells you which directories contain the largest amounts of data.
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That can help you narrow your search to the things most worth
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deleting.
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However, that only tells you what's big. What you really want to
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know is what's too big. By itself, du won't let you distinguish
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between data that's big because you're doing something that needs
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it to be big, and data that's big because you unpacked it once and
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forgot about it.
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Most Unix file systems, in their default mode, helpfully record
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when a file was last accessed. Not just when it was written or
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modified, but when it was even read. So if you generated a large
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amount of data years ago, forgot to clean it up, and have never
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used it since, then it ought in principle to be possible to use
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those last-access time stamps to tell the difference between that
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and a large amount of data you're still using regularly.
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agedu is a program which does this. It does basically the same sort
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of disk scan as du, but it also records the last-access times of
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everything it scans. Then it builds an index that lets it efficiently
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generate reports giving a summary of the results for each subdirectory,
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and then it produces those reports on demand.
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