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data from MySQL missing

Posted on 2011-03-02
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Last Modified: 2012-05-11
Hi,

Some data from our MySQL tables has just gone missing at random. There is no commonality between the data, just information here and there is now gone. This is a custom built PHP based CMS web application which was running fine for several months. We have have looked at the code and have not found any malicious code or worms.

How should we be doing to tackel this problem? Appreciate any help.

Thanks
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Question by:Web_Sight
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by:pius_babbun
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If you could check your sever log you may find some hooks to get to know what had caused this problem. Try to get the log based on you web server and mysql configuration.
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by:Mark Brady
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Do you have a cron job setup to backup the mysql tables or complete databases at regular intervals? If so you are in luck but if not the data is lost for good.
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by:mattibutt
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If its a cms then the user who manage the application might have accidently deleted other possibility is database is corrupted have you made backup of the database how much data do you think is missing.
I would say change the password of the database also monitor cms admins and change their password as well
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mwiercin earned 250 total points
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Few things you can look into :

1. Check if by any chance you will have full query log enabled:

mysql> show variables like 'log';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log           | OFF   | 
+---------------+-------+
1 row in set (0.00 sec)

Open in new window


If you have it ON consult your my.cnf for the  path  (at the database server) to full query log (it will be raw text file), of which you can derive what queries have deleted your data. Next step would be to trace them back to the part of application and collate with web server logs.

2. You may also have binary logging enabled (this is used primarily for cross database replication), check by

mysql> show variables like 'log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_bin       | ON   | 
+---------------+-------+
1 row in set (0.00 sec)

Open in new window

In such case check my.cnf variable log_bin. It will show you the pattern used for binary logs. i.e.

log_bin                 = /mnt/mysql.data/mysql-bin.log

Open in new window


, where you will find bunch of files starting with this name and suffixed with numbers. These are partial binary, but you can examine them easily by using command line tool mysqlbinlog.

3. If you don't have full or binary log, your last resort would be to look into slow query log

mysql> show variables like 'log_slow_queries';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| log_slow_queries | ON   | 
+------------------+-------+
1 row in set (0.00 sec)

Open in new window


Again you will find the exact location in my.cnf. Unfortunately this will include the queries only if they took more time then defined threshold (some MySQL distributions come with 2 seconds  preconfigured).

If you don't have any of these three logs, then unfortunately there is nothing more that would help you at MySQL level. I recommend auditing websever and/or application logs if you have any. Also, you can easily audit grants by using Perl tool http://maatkit.org/get/mk-show-grants.
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Author Closing Comment

by:Web_Sight
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not a good answer
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