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How To Verify And Test Unix File Archive/Backup

  • By on June 20, 2009 | No Comments

    Each time in our corporate IT operations, we have our backup running in place maybe on daily/weekly/monthly

    The application & database backup was directly spooled into the backup tape device.

    Is very important to verify tar command completed without any error just to ensure the backup files was usable when comes to disaster recovery.

    How can you verify the reliability of an archive? The tar command with -d (difference) option will show any files that are different in the archive from their originals on the disk. If this is done immediately after a backup, you should be prompt back without output.

    If you include -v, it would have listed every file on the tape as it examined and printed any errors after the end of the filename.

    You can do this some time after the backup, and tar -d option will tell you what has changes in your system after the backup.

    $ tar -cvf smartoptimizer.tar smartoptimizer
    smartoptimizer/
    smartoptimizer/config.php
    smartoptimizer/index.php
    smartoptimizer/LICENSE
    smartoptimizer/CHANGELOG
    smartoptimizer/minifiers/
    smartoptimizer/minifiers/js.php
    smartoptimizer/minifiers/css.php
    smartoptimizer/README
    smartoptimizer/cache/
     
    $ tar -df smartoptimizer.tar
     
    $ tar -tvf smartoptimizer.tar
    drwxr-xr-x oracle/oracle 0 2009-06-16 06:52:42 smartoptimizer/
    -rw-r--r-- oracle/oracle 1722 2008-12-16 01:54:38 smartoptimizer/config.php
    -rw-r--r-- oracle/oracle 6837 2008-12-16 01:55:09 smartoptimizer/index.php
    -rw-r--r-- oracle/oracle 35147 2008-12-05 23:53:17 smartoptimizer/LICENSE
    -rw-r--r-- oracle/oracle  2819 2008-12-16 02:59:58 smartoptimizer/CHANGELOG
    drwxr-xr-x oracle/oracle     0 2009-06-16 06:50:06 smartoptimizer/minifiers/
    -rw-r--r-- oracle/oracle  3163 2008-12-06 09:48:44 smartoptimizer/minifiers/js.php
    -rw-r--r-- oracle/oracle  3222 2008-12-16 02:47:32 smartoptimizer/minifiers/css.php
    -rw-r--r-- oracle/oracle  2563 2008-12-06 02:45:00 smartoptimizer/README
    drwxr-xr-x oracle/oracle     0 2009-06-20 20:04:38 smartoptimizer/cache/

    Now you realize I used another tar with -t option just to view the content of an archive file. With the -v option, you will see the owner and permission of the file whereas without it you will see the normal file listing.

    $ tar -cvzf smartoptimizer.tgz smartoptimizer
    smartoptimizer/
    smartoptimizer/config.php
    smartoptimizer/index.php
    smartoptimizer/LICENSE
    smartoptimizer/CHANGELOG
    smartoptimizer/minifiers/
    smartoptimizer/minifiers/js.php
    smartoptimizer/minifiers/css.php
    smartoptimizer/README
    smartoptimizer/cache/
     
    $ tar -df smartoptimizer.tgz
    tar: This does not look like a tar archive
    tar: Skipping to next header
    tar: Archive contains obsolescent base-64 headers
    tar: Error exit delayed from previous errors
     
    $ tar -tvf smartoptimizer.tgz
    tar: This does not look like a tar archive
    tar: Skipping to next header
    tar: Archive contains obsolescent base-64 headers
    tar: Error exit delayed from previous errors
    $ tar -cvzf smartoptimizer.tar.gz smartoptimizer
    smartoptimizer/
    smartoptimizer/config.php
    smartoptimizer/index.php
    smartoptimizer/LICENSE
    smartoptimizer/CHANGELOG
    smartoptimizer/minifiers/
    smartoptimizer/minifiers/js.php
    smartoptimizer/minifiers/css.php
    smartoptimizer/README
    smartoptimizer/cache/
     
    $ tar -df smartoptimizer.tar.gz
    tar: This does not look like a tar archive
    tar: Skipping to next header
    tar: Archive contains obsolescent base-64 headers
    tar: Error exit delayed from previous errors
     
    $ tar -tvf smartoptimizer.tar.gz
    tar: This does not look like a tar archive
    tar: Skipping to next header
    tar: Archive contains obsolescent base-64 headers
    tar: Error exit delayed from previous errors

    From the prompt that you saw above, the tar -d or tar -t doesn’t support for compressed tarball with .tgz or .tar.gz extension.

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