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CT console feature [message #45300] Thu, 23 February 2012 14:39 Go to next message
kir is currently offline  kir
Messages: 1645
Registered: August 2005
Location: Moscow, Russia
Senior Member

From: *parallels.com
I am glad to announce CT console feature.

Available in RHEL6-based kernel since 042stab048.1, this feature is
pretty simple to use. Use vzctl attach CTID to attach to this
container's console, and you will be able to see all the messages CT
init is writing to console, or run getty on it, or anything else.

Please note that the console is persistent, i.e. it is available even if
a container is not running. That way, you can run vzctl attach and then
(in another terminal) vzctl start. That also means that if a container
is stopped, vzctl attach is still there.

Press Esc . to detach from the console.

The feature will be available in up-coming vzctl-3.0.31. I have just
made a nightly build of vzctl (version 3.0.30.2-18.git.a1f523f)
available so you can test this. Check
http://wiki.openvz.org/Download/vzctl/nightly for information of how to
get a nightly build.

For anyone interested in user-space implementation of this, check this
git commit:
http://git.openvz.org/?p=vzctl;a=commitdiff;h=a1f523f59a6e321ce2cc6dd42d0f5a660a712339


Kir Kolyshkin
http://static.openvz.org/userbars/openvz-developer.png
Re: CT console feature [message #45305 is a reply to message #45300] Thu, 23 February 2012 16:18 Go to previous messageGo to next message
Tim Small is currently offline  Tim Small
Messages: 24
Registered: April 2011
Junior Member
From: *parallels.com
On 23/02/12 14:39, Kir Kolyshkin wrote:
> I am glad to announce CT console feature.

Very cool - been on my wish list for a while!

> Available in RHEL6-based kernel since 042stab048.1, this feature is
> pretty simple to use. Use vzctl attach CTID to attach to this
> container's console, and you will be able to see all the messages CT
> init is writing to console, or run getty on it, or anything else.
>
> Please note that the console is persistent, i.e. it is available even
> if a container is not running. That way, you can run vzctl attach and
> then (in another terminal) vzctl start. That also means that if a
> container is stopped, vzctl attach is still there.
>
> Press Esc . to detach from the console.

Cool. Just a thought on this escape sequence... ipmitool and ssh
(amongst others) use ~ after a carriage return as the command sequence,
and this is sort-of a defacto standard...

OpenSSH..


tim@ermintrude:~$ ~?
Supported escape sequences:
~. - terminate connection (and any multiplexed sessions)
[....]
~? - this message
~~ - send the escape character by typing it twice
(Note that escapes are only recognized immediately after newline.)


ipmitool

Special escape sequences are provided to control the SOL session:
~. Terminate connection
~^Z Suspend ipmitool
~^X Suspend ipmitool, but don't
restore tty on restart
~B Send break
~~ Send the escape character by
typing it twice
~? Print the supported escape sequences
Note that escapes are only recognized immediately
after newline.


Both allow you do change the escape character with a command line switch.

Any chance of adopting this "standard" instead of something else?

Any thoughts?

Cheers,

Tim.

--
South East Open Source Solutions Limited
Registered in England and Wales with company number 06134732.
Registered Office: 2 Powell Gardens, Redhill, Surrey, RH1 1TQ
VAT number: 900 6633 53 http://seoss.co.uk/ +44-(0)1273-808309
Re: CT console feature [message #45310 is a reply to message #45305] Thu, 23 February 2012 20:38 Go to previous messageGo to next message
kir is currently offline  kir
Messages: 1645
Registered: August 2005
Location: Moscow, Russia
Senior Member

From: *parallels.com
On 02/23/2012 08:18 PM, Tim Small wrote:
> On 23/02/12 14:39, Kir Kolyshkin wrote:
>> I am glad to announce CT console feature.
> Very cool - been on my wish list for a while!
>
>> Available in RHEL6-based kernel since 042stab048.1, this feature is
>> pretty simple to use. Use vzctl attach CTID to attach to this
>> container's console, and you will be able to see all the messages CT
>> init is writing to console, or run getty on it, or anything else.
>>
>> Please note that the console is persistent, i.e. it is available even
>> if a container is not running. That way, you can run vzctl attach and
>> then (in another terminal) vzctl start. That also means that if a
>> container is stopped, vzctl attach is still there.
>>
>> Press Esc . to detach from the console.
> Cool. Just a thought on this escape sequence... ipmitool and ssh
> (amongst others) use ~ after a carriage return as the command sequence,
> and this is sort-of a defacto standard...
>
> OpenSSH..
>
>
> tim@ermintrude:~$ ~?
> Supported escape sequences:
> ~. - terminate connection (and any multiplexed sessions)
> [....]
> ~? - this message
> ~~ - send the escape character by typing it twice
> (Note that escapes are only recognized immediately after newline.)
>
>
> ipmitool
>
> Special escape sequences are provided to control the SOL session:
> ~. Terminate connection
> ~^Z Suspend ipmitool
> ~^X Suspend ipmitool, but don't
> restore tty on restart
> ~B Send break
> ~~ Send the escape character by
> typing it twice
> ~? Print the supported escape sequences
> Note that escapes are only recognized immediately
> after newline.
>
>
> Both allow you do change the escape character with a command line switch.
>
> Any chance of adopting this "standard" instead of something else?
>
> Any thoughts?

See, the problem here is you usually access your node through ssh, and
if we will use the same sequence than ssh will close.

Having said that, I welcome patches that
- make accept the sequence only after a newline
- make an option and/or config parameter to change Esc to something else

>
> Cheers,
>
> Tim.
>


Kir Kolyshkin
http://static.openvz.org/userbars/openvz-developer.png
Re: CT console feature [message #45311 is a reply to message #45310] Thu, 23 February 2012 21:15 Go to previous messageGo to next message
Solar Designer is currently offline  Solar Designer
Messages: 5
Registered: August 2011
Junior Member
From: *parallels.com
Kir,

Thanks for your work on this!

On Fri, Feb 24, 2012 at 12:38:46AM +0400, Kir Kolyshkin wrote:
> See, the problem here is you usually access your node through ssh, and
> if we will use the same sequence than ssh will close.

Not necessarily. The person will need to type ~~. (or ~~~., etc.) to
get to the desired nesting level. This is already the case with ssh in
ssh (which is usually a bad idea for security reasons, but still), as
well as with certain other tools in a ssh session.

> Having said that, I welcome patches that
> - make accept the sequence only after a newline

Isn't this the same as making the sequence "<newline> ESC ." (or
"<newline> ~ .")?

> - make an option and/or config parameter to change Esc to something else

Sounds like a fine feature.

Alexander
Re: CT console feature [message #45314 is a reply to message #45300] Fri, 24 February 2012 08:40 Go to previous messageGo to next message
Tim Small is currently offline  Tim Small
Messages: 24
Registered: April 2011
Junior Member
From: *parallels.com
On 23/02/12 17:12, Kirill Kolyshkin wrote:
> Using ~. would be problematic since it interferes with e.g. ssh.
>

Hmm, on reflection, I can see "ESC ." possibly causing accidental
escapes when using vi? A reasonably common vi sequence is to insert a
body of text, and then repeat that insert. Wouldn't it be better to
make the escape ~ as-standard, and allow changing to escape too? I
can't think of a time when I've accidentally triggered the ~ sequence in
ssh...

> Patches to allow changing escape sequence and to only recognise it after a newline are welcome.
>

I'd be willing to contribute such a patch, but I have no spare time for
the next few months (I'm putting an extra storey on my house, and I
don't have much of a roof at the moment - so that's priority A1 for the
foreseeable).

Cheers,

Tim.

--
South East Open Source Solutions Limited
Registered in England and Wales with company number 06134732.
Registered Office: 2 Powell Gardens, Redhill, Surrey, RH1 1TQ
VAT number: 900 6633 53 http://seoss.co.uk/ +44-(0)1273-808309
Re: CT console feature [message #45404 is a reply to message #45300] Sat, 03 March 2012 04:04 Go to previous message
ragubhat is currently offline  ragubhat
Messages: 9
Registered: August 2008
Location: India
Junior Member
From: *parallels.com
Kir announces:

>> Use vzctl attach CTID to attach to this container's console, and you
>> will be able to see all the messages CT init is writing to console

Real cool feature, thanks for your work on improving vzctl and friends.

--
Regards
Raghavendra Bhat
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