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Date: Fri, 8 Sep 2017 20:53:57 +0200
From: David Sterba <dsterba@suse.cz>
To: linux-btrfs@vger.kernel.org
Subject: Re: test if a subvolume is a snapshot?
Message-ID: <20170908185357.GW31874@twin.jikos.cz>
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References: <20170908085446.GA7876@rus.uni-stuttgart.de>
 <20170908131035.GO31874@twin.jikos.cz>
 <20170908184157.GB7876@rus.uni-stuttgart.de>
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On Fri, Sep 08, 2017 at 08:41:57PM +0200, Ulli Horlacher wrote:
> On Fri 2017-09-08 (15:10), David Sterba wrote:
> > On Fri, Sep 08, 2017 at 10:54:46AM +0200, Ulli Horlacher wrote:
> > 
> > > How can I test if a subvolume is a snapshot?
> > 
> > The inode number is 256 on a btrfs filesystem:
> > 
> > if [ stat -f --format=%T $path = btrfs -a stat --format=%i $path = 256 ]; ...
> > 
> > The directory that's result of snapshotting a subvolume, also called
> > EMPTY_SUBVOL has inode number 2, but that's not considered a normal
> > subvolume.
> 
> This is not true.

Oh I see, I've read the mail too quickly sorry, not just a subvolume but
really a snapshot. Then the simple inode number check does not work of
cours, the answer is more or less what Peter Grandi replied.