yum-fs-snapshot btrfs howto?

[Neal Becker]

Chris Murphy wrote:

> 
> On Jan 16, 2014, at 11:21 AM, Neal Becker <ndbecker2 at gmail.com> wrote:
>> 
>> I'm talking only about yum-fs-snapshot.
> 
> Yeah I haven't used it.
> 
>>  When I run yum it's never going to
>> write into /home.  But I don't know exactly what this means.
> 
> And when you do a yum update, do you get a snapshot in /home?
> 
>>  Notice my /home
>> and / root partition are the same physical device (which is fedora's default
>> install on btrfs - or at least was when I did the original install).
> 
> Yes.
> 
> 
>> So I'm guessing yum-fs-snapshot will snapshot everything - since it does
>> snapshot or root.  Does additional snapshot of /home actually do anything?
> 
> I'm not sure what you mean by additional. What's the first instance? Snapshots
> do not recursively snapshot subvolumes. For example:
> 
> 274	5517	5		<FS_TREE>/home.0
> 476	5344	5		<FS_TREE>/home.0/chris/Downloads/git
> 488	5352	5		<FS_TREE>/home.0/chris/Downloads/git/kernel
> 
> 
> If I snapshot ID 274, the resulting subvolume will stop at a directory
> ./chris/Downloads/git which will be empty. So it's not going to contain any
> reference at all to the subvolumes that were in the original subvolume.
> 
> 
> Chris Murphy
> 
When running yum update:
...
fs-snapshot: snapshotting /: /yum_20140116082354
fs-snapshot: snapshotting /home/: /home/yum_20140116082354

After running a couple of updates:

sudo btrfs subvolume list /
[sudo] password for nbecker: 
ID 256 gen 563200 top level 5 path home
ID 258 gen 563200 top level 5 path root
ID 366 gen 563175 top level 258 path yum_20140116082354
ID 367 gen 563177 top level 5 path home/yum_20140116082354
ID 368 gen 563184 top level 258 path yum_20140116082704
ID 369 gen 563186 top level 5 path home/yum_20140116082704

So I'm thinking it is doing unnecessary snapshotting of /home?