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On Sunday 24 February 2008, Stroller wrote: |
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> I've done this loads in the past, and never been aware of any file |
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> corruption, but I guess I'm just paranoid today. Perhaps I shouldn't |
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> use the -v flags during my copy - it's reassuring to see the files |
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> being copied, but what if I overlooked a bunch of errors in the |
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> middle of all those thousands of "copied successfully" confirmations? |
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> What if something has gone wrong during one of the two copies? |
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Well, in that case cp will have a nnonzero exit status. Look: |
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|
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$ ls -l |
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total 12 |
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-rw-r--r-- 1 kermit users 4 2008-02-24 12:30 a |
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-rw-r--r-- 1 kermit users 12 2008-02-24 12:30 b |
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drwxr-xr-x 2 kermit users 4096 2008-02-24 12:30 destdir |
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$ ls -l destdir |
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total 0 |
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$ chmod 000 b |
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$ ls -l |
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total 12 |
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-rw-r--r-- 1 kermit users 4 2008-02-24 12:30 a |
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---------- 1 kermit users 12 2008-02-24 12:30 b |
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drwxr-xr-x 2 kermit users 4096 2008-02-24 12:30 destdir |
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$ cp a b destdir |
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cp: cannot open `b' for reading: Permission denied |
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$ echo $? |
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1 |
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$ ls -l destdir |
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total 4 |
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-rw-r--r-- 1 kermit users 4 2008-02-24 12:31 a |
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I think this should hold for the majority of cases/errors cp might |
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encounter during the copy. |
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Of course, this does not detect a succesful, but somehow corrupted, copy |
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(which should be exceptionally rare, anyway). |
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> So my question is: |
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> |
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> Is there any way to check the integrity of copied directories, to be |
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> sure that none of the files or sub-directories in them have become |
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> damaged during transfer? I'm thinking of something like md5sum for |
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> directories. |
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I'm not aware of any such tool (which might exist nonetheless, of |
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course). However, on the filesystem, the objects that we |
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call "directories" are just index files holding filenames and pointers |
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to inodes. Running a checksum on the directories themselves would not |
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guarantee against corruption of any of the contained files, since file |
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data is not contained in the directory. Thus, to be accurate, such a |
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tool would have to scan the directory, find each file, and perform a |
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checksum on it, which would result in something not much different from |
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the find command you suggested, in terms of resource usage. |
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-- |
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