On 03/02/2014 11:26 AM, Chris Murphy wrote:
On Feb 3, 2014, at 11:19 AM, Matthew Lai <m@xxxxxxxxxxxxx> wrote:
Thanks. I should clarify what I'm trying to do.
I'm trying to use btrfs send for backup, without having another btrfs volume.
So the initial backup is a complete send, piped to Amazon Glacier (so my machine never has the whole file, and doesn't have space for one).
OK so you've use btrfs send piped to Glacier which creates a *file*, I'll call it "initial", not a navigable directory of files? Right?
That is correct.
It looks like the problem now is the sent file can't be applied to the original volume (for restore).
I'm counting two sent files: initial, increment1. I'm not sure which one you're applying. If you have the exact same read-only snapshot that the btrfs send file "initial" is based on, then you'd apply the increment1 to that read-only snapshot which will cause a new read-only snapshot to be created with the incremental data applied to it. The error you're getting sounds like the parent read-only snapshot isn't available?
That is also correct. There are 2 sent files. I am trying to apply
increment1, on a snapshot of the parent (that was used to create
increment1).
I added -vv. Here is the test script for reproducing this entire setup.
-----------------------------------------------------------------------
#!/bin/sh
btrfs subvolume create data
btrfs subvolume snapshot -r data first_backup
touch data/a
btrfs subvolume snapshot -r data second_backup
btrfs send -p first_backup second_backup > increment
btrfs subvolume snapshot first_backup first_backup_rw
btrfs receive -vv first_backup_rw < increment
-----------------------------------------------------------------------
Output:
-----------------------------------------------------------------------
Create subvolume './data'
Create a readonly snapshot of 'data' in './first_backup'
Create a readonly snapshot of 'data' in './second_backup'
At subvol second_backup
Create a snapshot of 'first_backup' in './first_backup_rw'
At snapshot second_backup
receiving snapshot second_backup
uuid=e6159a2a-3430-344a-a23d-b9bb83851a63, ctransid=28
parent_uuid=20c4ff66-a9ec-fc44-93c6-2c12637e95e6, parent_ctransid=26
ERROR: could not find parent subvolume
-----------------------------------------------------------------------
I would think applying the "patch" to first_backup_rw should succeed,
because it's exactly the same as first_backup, which is the parent for
the send, but it doesn't.
Thanks
Matthew
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