Re: snapshots changed behavior

[Jim <jim@webstarts.com>]

Goffredo,
Thank you very much for your reply.  That was the information I needed 
to understand the behavior I was observing.  Just to be sure that I 
understand correctly, you wrote:

I am quite sure that the snapshot is NOT recursive. If a subvolume contains
another subvolume, and you snapshot the former, the new subvolume shall not
contain the "child" subvolume.

when I snapshot /data, a subvolume I can see (but not enter) the 
subvolume /sites below it.  When I snapshot subvolume /sites I can see 
and navigate through all directories (not subvolumes) below it.  I am 
assuming that this is expected behavior.  Thanks again for taking the 
time to help me here.
Jim

On 10/21/2011 01:53 PM, Goffredo Baroncelli wrote:
> On Friday, 21 October, 2011 12:31:34 Jim wrote:
>> Good afternoon btrfs list,
> Hi Jim
>
>> about a month ago, when testing btrfs, I could create a snapshot with
>> btrfs snap create and be able to drill down in the snapshot to find
>> subvols and files below the snapshot level.  I currently need to use
>> btrfsctl -s to create snapshots and can no longer drill down through
>> subvols in them.  An example would be a file tree of /btrfs (subvol)
>> /data (subvol) /sites (subvol) /0000 (directory) /files-in-dir.  If I
>> snapshot /btrfs/data I can open data and see /sites but can see nothing
>> below /sites.  However, if I snap /btrfs/data/sites I can drill down
>> through all lower directories and files.  In my past tests I was able to
>> drill all the way down from the /btrfs/data snap.
> I am quite sure that the snapshot is NOT recursive. If a subvolume contains
> another subvolume, and you snapshot the former, the new subvolume shall not
> contain the "child" subvolume.
>
>  From what you report, it seems that /sites was a directory and not a snapshot.
>
> Pay attention that btrfsctl -s allow to take as source a directory. In this
> case this program snapshot the subvolume which contains the subdirectory
> passed as argument.
> Instead the btrfs tool checked if the source is a subvolume. If not it raises
> an error.
>
> I say so because the btrfctl behaviour confused a lot of people.
>
> In any case btrfs was never been capable to snapshot a directory.
>
>> Also, in the past, a
>> snap was definitely a sparse file and was able to easily be moved, moved
>> back, remounted and used.  Currently, the useful file /btrfs/data/sites
>> contains 5GB of data and both shows and moves as 5GB of data, not like a
>> sparse file.  Am I misusing the filesystem, or improperly using the
>> commands?  Or have changes been made to the functionality which I
>> missed?
> It is not allowed to move files between subvolume. The mv command in this case
> copies the files and removes the original ones.
>
>  From what you wrote it seems that (for mistake) you thought that a directory
> was a subvolume.
>
>> Sorry to take your time on such a simple matter, but I need to
>> understand how to best use the filesystem.  Thanks very much for your
>> advice.
>> Jim Maloney
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