Re: [Qemu-devel] qemu-img: document 'info --backing-chain

[Eric Blake <eblake@redhat.com>]

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On 10/13/2012 11:30 PM, Kashyap Chamarthy wrote:
>>From a6233277e17338f571dda27cd9192d764f824b18 Mon Sep 17 00:00:00 2001
> From: Kashyap Chamarthy <kashyap.cv@gmail.com>
> Date: Sun, 14 Oct 2012 09:51:18 +0530
> Subject: [PATCH v2] qemu-img: document 'info --backing-chain'
> 
> Signed-off-by: Kashyap Chamarthy <kashyap.cv@gmail.com>
> ---
>  qemu-img-cmds.hx |  4 ++--
>  qemu-img.texi    | 19 ++++++++++++++++++-
>  2 files changed, 20 insertions(+), 3 deletions(-)

Per http://wiki.qemu.org/Contribute/SubmitAPatch, it helps to add a
maintainer in cc; I'm guessing that this is most closely related to
block work, and therefore adding Kevin in cc.

Reviewed-by: Eric Blake <eblake@redhat.com>

Also, it helps to call out your specific pre-requisite; this only makes
sense after Stefan's patches:
https://lists.gnu.org/archive/html/qemu-devel/2012-10/msg02527.html

> 
> diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
> index 0ef82e9ac7a89d607e1f2c8e38461cee5b438dba..a18136302d2ca7a7540672f1b9ef89603e89edc0 100644
> --- a/qemu-img-cmds.hx
> +++ b/qemu-img-cmds.hx
> @@ -34,9 +34,9 @@ STEXI
>  ETEXI
>  
>  DEF("info", img_info,
> -    "info [-f fmt] [--output=ofmt] filename")
> +    "info [-f fmt] [--output=ofmt] [--backing-chain] filename")
>  STEXI
> -@item info [-f @var{fmt}] [--output=@var{ofmt}] @var{filename}
> +@item info [-f @var{fmt}] [--output=@var{ofmt}] [--backing-chain] @var{filename}
>  ETEXI
>  
>  DEF("snapshot", img_snapshot,
> diff --git a/qemu-img.texi b/qemu-img.texi
> index 8b05f2c42801a2535ab4390b47bc415eb880625a..ffd334dc7b049c50474be88376acd5267ad96c3c 100644
> --- a/qemu-img.texi
> +++ b/qemu-img.texi
> @@ -28,6 +28,10 @@ Command parameters:
>  is the disk image format. It is guessed automatically in most cases. See below
>  for a description of the supported disk formats.
>  
> +@item --backing-chain 
> +will enumerate information about backing files in a disk image chain. Refer
> +below for further description.
> +
>  @item size
>  is the disk image size in bytes. Optional suffixes @code{k} or @code{K}
>  (kilobyte, 1024) @code{M} (megabyte, 1024k) and @code{G} (gigabyte, 1024M)
> @@ -129,7 +133,7 @@ created as a copy on write image of the specified base image; the
>  @var{backing_file} should have the same content as the input's base image,
>  however the path, image format, etc may differ.
>  
> -@item info [-f @var{fmt}] [--output=@var{ofmt}] @var{filename}
> +@item info [-f @var{fmt}] [--output=@var{ofmt}] [--backing-chain] @var{filename}
>  
>  Give information about the disk image @var{filename}. Use it in
>  particular to know the size reserved on disk which can be different
> @@ -137,6 +141,19 @@ from the displayed size. If VM snapshots are stored in the disk image,
>  they are displayed too. The command can output in the format @var{ofmt}
>  which is either @code{human} or @code{json}.
>  
> +If a disk image has a backing file chain, information about each disk image in
> +the chain can be recursively enumerated by using the option @code{--backing-chain}.
> +
> +For instance, if you have an image chain like: 
> +
> +    base.qcow2 <- snap1.qcow2 <- snap2.qcow2 
> +
> +To enumerate information about each disk image in the above chain, starting from top to base, do:
> +    
> +    @example
> +    qemu-img info --backing-chain snap2.qcow2
> +    @end example
> +
>  @item snapshot [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot} ] @var{filename}
>  
>  List, apply, create or delete snapshots in image @var{filename}.
> 

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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