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Re: [Xen-devel] [PATCH] xen/console: introduce a 'w' debug-key that dumps the console ring

  • To: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>
  • From: Keir Fraser <keir@xxxxxxx>
  • Date: Mon, 01 Oct 2012 16:50:31 +0100
  • Cc: Matt Wilson <msw@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxx
  • Delivery-date: Mon, 01 Oct 2012 15:51:14 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: Ac2f7HxKeaFQ8guH5k+BeWgRVg3xUA==
  • Thread-topic: [Xen-devel] [PATCH] xen/console: introduce a 'w' debug-key that dumps the console ring

On 01/10/2012 16:18, "Ian Jackson" <Ian.Jackson@xxxxxxxxxxxxx> wrote:

> Jan Beulich writes ("Re: [Xen-devel] [PATCH] xen/console: introduce a 'w'
> debug-key that dumps the console ring"):
>> On 29.09.12 at 20:49, Matt Wilson <msw@xxxxxxxxxx> wrote:
>>> It would have been. But what if no one was looking, or dom0 cleared
>>> the console, or placed it into a scrolling mode that prevents a
>>> virtual terminal from placing output into a scrollback buffer. With
>>> this patch, you can connect to a serial console after a machine
>>> becomes unresponsive and gather clues on what went wrong.
>> That's an operator error then.
> Speaking as someone who does some sysadmin in their spare time, I
> think this would be a very useful feature.  It is often the case that,
> best intentions notwithstanding, the arrangements for collecting
> serial output fail.  Many serial concentrators and ipkvms are very
> bad.

Yes, I must say that I found Matt's explanation quite compelling too.
Clearly a large user of Xen is finding it useful, or it would not have been
proposed. ;)

So I will probably take the patch, and indeed running out of keys is a poor
reason for rejecting, as we can switch to two letter combos or a really
simple shell for extended commands.

 -- Keir

>> I completely agree with Keir that what you propose is pretty
>> questionable (and you provide one argument against it already - the
>> shortage of remaining keys).
> If necessary we can have multi-keystroke keys, surely.  We should
> start with assigning a prefix punctuation character which will give us
> another 52 letters to play with.
> Ian.

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