Re: btrfs send / receive via netcat, fails halfway?

[Hugo Mills <hugo@carfax.org.uk>]

On Sun, Jan 10, 2021 at 11:34:27AM +0100,   wrote:
> ­I'm trying to transfer a btrfs snapshot via the network.
> 
> First attempt: Both NC programs don't exit after the transfer is complete. When I ctrl-C the sending side, the receiving side exits OK.
> 
> btrfs subvolume delete /mnt/rec/snapshots/*
> receive side:
> # nc -l -p 6790 | btrfs receive /mnt/rec/snapshots
> At subvol 0
> 
> sending side:
> # btrfs send  /mnt/send/snapshots/0 | nc -v 127.0.0.1 6790
> At subvol /mnt/send/snapshots/0
> localhost [127.0.0.1] 6790 (hnmp) open

   Use -q 15 on the sending side. That will exit after 15 seconds of
no activity from the send process.

> Second attempt: both nc programs exit ok at snapshot 0,1,2, but snapshot3 fails halfway, and 4 fails, as 3 is not complete. 
> receive side:
> # nc -l -p 6790 | btrfs receive /mnt/rec/snapshots
> At subvol 0
> # nc -l -p 6790 | btrfs receive /mnt/rec/snapshots
> At snapshot 1
> # nc -l -p 6790 | btrfs receive /mnt/rec/snapshots
> At snapshot 2
> # nc -l -p 6790 | btrfs receive /mnt/rec/snapshots
> At snapshot 3
> read(net): Connection reset by peer
> ERROR: short read from stream: expected 49183 read 10450

   This failed because of a network disconnect.

> # nc -l -p 6790 | btrfs receive /mnt/rec/snapshots
> At snapshot 4
> ERROR: cannot find parent subvolume
> write(stdout): Broken pipe

   This is expected because the previous one failed.

   There's no btrfs problem here. You just need better error handling
(to retry a failed transfer, for example).

   Hugo.

-- 
Hugo Mills             | How do you become King? You stand in the marketplace
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