On Fri, Mar 06, 2015 at 07:39:36AM +0000, Chen, Hanxiao wrote:
> -----Original Message-----
> From: Richard W.M. Jones [mailto:rjones@redhat.com]
> Sent: Thursday, March 05, 2015 8:59 PM
> To: Chen, Hanxiao/陈 晗霄
> Cc: libguestfs(a)redhat.com
> Subject: Re: [Libguestfs] [PATCH 1/2] New API: btrfs_filesystem_show
>
> AFAICT this API doesn't work:
>
> $ ./run guestfish -N fs:btrfs btrfs-filesystem-show /dev/sda1
> libguestfs: error: btrfs_filesystem_show: /dev/sda1:
>
That might be a bug of btrfs-progs. v3.17 works fine.
I'll fix it.
> When I tried the btrfs-filesystem-show-all API, I see a lot of
> structure in the output:
>
> $ ./run guestfish -N fs:btrfs btrfs-filesystem-show-all
> Label: none uuid: f7754d86-baa1-40e7-a563-46976e81d64c
> Total devices 1 FS bytes used 28.00KiB
> devid 1 size 99.88MiB used 12.00MiB path /dev/sda1
>
> Btrfs v3.18
>
> Usually we should try to turn that text into structs, otherwise every
> consumer of libguestfs has to write parsing code themselves.
>
> *However* in this case I'm having a hard time understanding why anyone
> would want to use the API. Most likely if they were debugging a btrfs
> problem, they'd be using 'virt-rescue' and would be able to run
> arbitrary commands. Some of the other information, like UUID and
> label is available through other APIs (eg. get-uuid). Other
> information like the layout of devices could be modelled with some
> very complex structs on the libguestfs side, but does anyone need
> this?
>
btrfs filesystem show could tell user info when they what to use:
btrfs filesystem balance
What's more,
it could tell us if some of the btrfs device is missing:
If we had 10 btrfs devices but one of them is missing, we could use
btrfs-filesystem-show to find out which one is missing in a convenient way.
I don't doubt that it's useful, but these kind of user-facing
debugging operations would probably be done using 'virt-rescue'.
Rich.
--
Richard Jones, Virtualization Group, Red Hat
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