Libguestfs - Jan 2022 - [PATCH v2v 2/2] v2v: Send nbdinfo debug information to stderr not stdout

When running in verbose mode (virt-v2v -vx) debug messages are
supposed to only be written to stderr.  This allows virt-p2v and other
wrappers to separate ordinary progress messages and warnings, from
debugging information.

However when we added nbdinfo output (only printed in verbose mode),
the output was wrongly sent to stdout instead of stderr.  You can show
this as follows:

$ virt-v2v -vx -i disk /var/tmp/fedora-35.qcow2 -o null 2>/dev/null
[   0.0] Setting up the source: -i disk /var/tmp/fedora-35.qcow2
[   1.0] Opening the source
... some messages elided ...
protocol: newstyle-fixed without TLS      <-- debug output to stdout
export="":
	export-size: 6442450944 (6G)
	content: DOS/MBR boot sector
	uri: nbd+unix:///?socket=/tmp/v2v.Xqvaml/in0
... etc ...

This patch sends the nbdinfo debugging output to stderr instead.

Reported-by: Tingting Zheng
Fixes: commit 255722cbf39afc0b012e2ac00d16fa6ba2f8c21f
---
 v2v/v2v.ml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/v2v/v2v.ml b/v2v/v2v.ml
index d74cc21f0a..a91d8cef8f 100644
--- a/v2v/v2v.ml
+++ b/v2v/v2v.ml
@@ -631,7 +631,7 @@ and nbdcopy output_alloc input_uri output_uri   *)
 and nbdinfo ?(content = false) uri    let cmd -    sprintf "nbdinfo%s
%s"
+    sprintf "nbdinfo%s %s >&2"
       (if content then " --content" else " --no-content")
(quote uri) in
   ignore (Sys.command cmd)
 
-- 
2.32.0

On 01/25/22 11:45, Richard W.M. Jones wrote:
> When running in verbose mode (virt-v2v -vx) debug messages are
> supposed to only be written to stderr.  This allows virt-p2v and other
> wrappers to separate ordinary progress messages and warnings, from
> debugging information.
> 
> However when we added nbdinfo output (only printed in verbose mode),
> the output was wrongly sent to stdout instead of stderr.  You can show
> this as follows:
> 
> $ virt-v2v -vx -i disk /var/tmp/fedora-35.qcow2 -o null 2>/dev/null
> [   0.0] Setting up the source: -i disk /var/tmp/fedora-35.qcow2
> [   1.0] Opening the source
> ... some messages elided ...
> protocol: newstyle-fixed without TLS      <-- debug output to stdout
> export="":
> 	export-size: 6442450944 (6G)
> 	content: DOS/MBR boot sector
> 	uri: nbd+unix:///?socket=/tmp/v2v.Xqvaml/in0
> ... etc ...
> 
> This patch sends the nbdinfo debugging output to stderr instead.
> 
> Reported-by: Tingting Zheng
> Fixes: commit 255722cbf39afc0b012e2ac00d16fa6ba2f8c21f
> ---
>  v2v/v2v.ml | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/v2v/v2v.ml b/v2v/v2v.ml
> index d74cc21f0a..a91d8cef8f 100644
> --- a/v2v/v2v.ml
> +++ b/v2v/v2v.ml
> @@ -631,7 +631,7 @@ and nbdcopy output_alloc input_uri output_uri >   *)
>  and nbdinfo ?(content = false) uri >    let cmd > -    sprintf
"nbdinfo%s %s"
> +    sprintf "nbdinfo%s %s >&2"
>        (if content then " --content" else "
--no-content") (quote uri) in
>    ignore (Sys.command cmd)
>  
> 
Reviewed-by: Laszlo Ersek <lersek at redhat.com>