Error when using btrfs subvolume snapshot & send | receive

Error when using btrfs subvolume snapshot & send | receive

[René Fricke-Müller]

Hello,

I have some trouble using btrfs snapshots on Ubuntu 19.10.

I am creating snapshots of my /-subvolume and use send | receive for 
incremental transferring. Sometimes I get errors like "ERROR: cannot 
open /media/Backup/OS/snapshots/snap_2020-05-13_11:39/o13170-19818-0: No 
such file or directory"

When I look deeper with the -v option, it seems like btrfs is creating a 
folder or something, moves it and then tries to rename the original folder.

The error occures on different devices, but only when I make snapshots 
of the root of my os subvolume. The error occures only from time to time 
(perhaps every 5th to 15th snapshot) the only solution to send a new 
snapshot complete and then send incremental snapshots.

I tried different kernels:
Currently I am using 5.3.0-51-generic on one device but also tried 5.5 
and 5.6.11.

I found this topic on github, where some people have the same errors. 
(but I am using an own script, not that program)

https://github.com/digint/btrbk/issues/223 
<https://github.com/digint/btrbk/issues/223>


Can you confirm this error and/or help me?


Kind Regards

René

Re: Error when using btrfs subvolume snapshot & send | receive

[Andrei Borzenkov]

13.05.2020 15:16, René Fricke-Müller пишет:
> Hello,
> 
> I have some trouble using btrfs snapshots on Ubuntu 19.10.
> 
> I am creating snapshots of my /-subvolume and use send | receive for
> incremental transferring. Sometimes I get errors like "ERROR: cannot
> open /media/Backup/OS/snapshots/snap_2020-05-13_11:39/o13170-19818-0: No
> such file or directory"
> 

You did not say whether error is on source or destination side.

> When I look deeper with the -v option, it seems like btrfs is creating a
> folder or something, moves it and then tries to rename the original folder.
> 


Still unclear whether it is send or receive.

> The error occures on different devices, but only when I make snapshots
> of the root of my os subvolume. The error occures only from time to time
> (perhaps every 5th to 15th snapshot) the only solution to send a new
> snapshot complete and then send incremental snapshots.
> 
> I tried different kernels:
> Currently I am using 5.3.0-51-generic on one device but also tried 5.5
> and 5.6.11.
> 
> I found this topic on github, where some people have the same errors.
> (but I am using an own script, not that program)
> 
> https://github.com/digint/btrbk/issues/223
> <https://github.com/digint/btrbk/issues/223>
> 

This describes error on destination. Such errors are indications that
btrfs finds wrong base snapshot to apply changes to. Does your source
subvolume has received UUID by any chance?

Output of

btrfs subvolume show <source>
btrfs subvolume show <target>

would be interesting.

> 
> Can you confirm this error and/or help me?
> 
> 
> Kind Regards
> 
> René