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Re: [Libguestfs] [PATCH 1/2] New API: btrfs_filesystem_show

> -----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 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.

- Chen

> Rich.
> --
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> virt-top is 'top' for virtual machines.  Tiny program with many
> powerful monitoring features, net stats, disk stats, logging, etc.
> http://people.redhat.com/~rjones/virt-top

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