[Box Backup] I have the fear....

[Chris Wilson]

Hi Ben,

On Tue, 13 Mar 2007, Chris Wilson wrote:

>>  You can see from the above the following history:
>>  1) host.conf (id 00000081/sum 01107) existed when the first backup was
>>    run.  This was the state before I updated the system and host.conf
>>    needed to be changed
>>  2) ._cfg0000_host.conf (0000171a/55758) was created pending the run
>>    of the tool that updates the real config files.  This has the new
>>    contents of the file.
>>  3) Update tool ran, moving ._cfg0000_host.conf to host.conf, and
>>    boxbackup spotted the change, but preserved the old contents as
>>    (0000171d/1107), exactly the same contents as the predecessor version.
>>  4) I touched host.conf
>>  5) boxbackup correctly updated the server (00006cbc/55758)
>
> OK, so it appears that Box Backup did not notice that ._cfg0000_host.conf was 
> moved over host.conf, and therefore did not back up host.conf again, until 
> you touched the file. Is that your understanding as well?
>
> If so, then it does indeed look like a bug in Box Backup. Thanks for 
> reporting it, I will investigate.

I think I have been able to reproduce this bug.

The problem is that both ._cfg0000_host.conf and host.conf had exactly 
the same modification time before the update tool ran, and host.conf had 
the same modification time afterwards. Because the modification time of 
host.conf did not change between backup runs, Box Backup assumed that the 
file had not changed, and skipped it.

I would consider it a bug in Gentoo that it touched host.conf without 
changing it, and therefore it ended up with the same timestamp as 
._cfg0000_host.conf.

We could fix this by comparing the inode numbers with our cached store as 
well, or perhaps even doing a full compare on the file, although the 
latter would probably slow down backups a lot (since every file which 
appears not to have been changed would have to be compared).

Cheers, Chris.
-- 
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