Re: [Qemu-devel] [PATCH] Add backing file option to qemu-img create help.

[Mike Day]

On Mon, May 12, 2014 at 12:36 PM, Kevin Wolf <address@hidden> wrote:
> What would qemu-img rebase do with -o? It is just for (safely) changing
> the backing file, not for updating options. There is qemu-img amend for
> that, and it does have an -o option.

A little background ... I'm writing a 4-day  KVM training course for
the Linux foundation. From time to time I come across undocumented,
buggy, or confusing options and if I can I try to fix them. In the
case of qemu-img I looked in a lot of places for documentation and
ended up at the unofficial web page that documented the -b backing
file option which works just fine for create and rebase. If an
official page had the information I needed in one place instead of
bits and pieces scattered everywhere I would have used it, naturally.

Here's why the help is confusing. On the top level help, all the
options except for -b are documented. A couple subcommands are even
listed in the top level help with their options. I expected that -b
would be documented on the top level with the others. The fact that -b
<basefile> is documented for the rebase subcommand reenforced my
expectation. I was assuming there is some consistency in using options
with backing files. (Especially if the option is called
"backingfile.")

I'm not advocating anything here, and I think its fine to leave things
as they are. I just don't want to be the guy who complains and never
fixes anything.

Mike