[Box Backup] Suggested change in behaviour

[Ben Summers]

On 20 Sep 2004, at 15:02, Richard Eigenmann wrote:

> Basically you want to stop the delete process when the directory at a
> mount point is not mounted and there was previously backed up data for
> that location.

Not precisely. I want to avoid marking files as deleted when there's 
absolutely nothing in that location -- which I believe will almost 
always be an indication that a Very Bad Thing has happened, and backups 
will be required ASAP.

>
> You recommend that each mount point should be backed up separately.

I require this!

> However you might find situations where people have mount points 
> further
> down the tree even if this is not such a good idea.

I must write the code which stops people from doing that.

>
> I wonder if there might not be a better way to detect an unmounted
> directory?

On BSDs, it should be trivially easy.

>  Use of fstab? But that doesn't help in your scenario. Perhaps
> have a list of mountpoints in the .conf file?

But I want to catch an obviously bad situation, not detect a specific 
bad situation.

>
> You could also have boxbackup run in "safe mode" by default (as you
> describe) and use a --force-delete switch to ensure that wiped root
> directories get marked as deleted in the archive.
>
> The warning message could read something like "Directory not mounted or
> empty. Use command xxx to delete it's contents from the backup 
> archive."
>
> Such a switch/command could for instance be useful for new users who 
> are
> setting up boxbackup and back up a small directory first and then 
> change
> the location of their root to back up everything. This would be
> something like forcing the garbage collection. But that should perhaps
> be called --force-gc and you have already made suggestions how this can
> be triggered.

How about adding a flag

   EmptyLocationSafety = [yes|no]

in the location records, which defaults to "yes"? (and mentioning this 
in the log message)

Ben



>
>
> On Mon, 2004-09-20 at 15:39, Ben Summers wrote:
>>
>> Imagine this scenario. You have a single partition on a hard drive,
>> mounted as /home. This drive fails, the server reboots, but fails to
>> pass fsck checks as much is unreadable. You modify /etc/fstab so it
>> isn't mounted, and reboot. The machine comes up.
>>
>> Unfortunately, you forgot to disable bbackupd running on boot, which
>> you've got running in lazy mode. It runs, does it's initial scan, and
>> marks everything in this partition as deleted.
>>
>> This is unlikely to help the situation much, and incidentally, has 
>> just
>> happened to me. (Fortunately, I have "undelete" technology hidden in
>> the server, and have just written a bit of code to allow access to it
>> via bbackupquery, so it's not a calamity - even if it has also
>> undeleted files which were deleted by the users before the partition
>> vanished.)
>>
>> I propose a slight change in behaviour which may go some way towards
>> resolving this problem, but I wonder if it will cause any other 
>> issues.
>>
>> * If bbackupd finds that the root of a Location (as specified in
>> bbackupd.conf) contains no files or directories, it
>>
>>     - will log a message "Backup location /x is empty, not changing
>> store" at level LOG_ERR
>>
>>     - will not modify the relevant location on the server
>>
>> Can anyone see any situation where this might cause problems? This 
>> will
>> only be triggered if there's absolutely nothing to back up in a
>> location.
>>
>> Thanks,
>>
>> Ben
>>
>>
>>
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> -- 
> Richard Eigenmann <richard_eigenmann@compuserve.com>
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