Re: (pspace,pid) vs true pid virtualization

[Herbert Poetzl <herbert@13thfloor.at>]

On Mon, Feb 20, 2006 at 05:34:33PM +0300, Kirill Korotaev wrote:
>>> yes, acceptable.
>>> once, again, believe me, this is very required feature for
>>> troubleshouting and management (as Eric likes to take about
>>> maintanance :) )
> 
>> IMHO there are certain things which _are_ required
>> and others which are nice to have but not strictly
>> required, just think "ptrace across pid spaces"
> these "nice to have" features often make one solution more usable than
> another.

agreed, but do you really have to strace the OpenVZ
tools so often, as I don't see any other purpose 
for cross space strace. usually you strace either
inside or outside the space, as the transition is
not that well defined anyway ...

>>>> This is to support using pidspaces for vservers, and creating
>>>> migrateable sub-pidspaces in each vserver.

>>> this doesn't help to create migratable sub-pidspaces.
>>> for example, will you share IPCs in your pid parent and child pspaces?
>>> if yes, then it won't be migratable;

>> well, not the child pspace, but the parent, no?

> if IPC objects are shared between them, then they can only be migrated 
> together.

not all spaces will be done fur the purpose of
migration, some of them might have other purposes

>>> if no, then you need to create fully isolated spaces to the end and
>>> again you end up with a question, why nested pspaces are required at
>>> all?
>> because we are not trying to implement a VPS only
>> solution for mainline, we are trying to provide
>> building blocks for many different uses, including
>> the VPS approach ...
> nice! do you think I'm against building blocks? no :) 

> I'm just trying to get out from you how this can be used in real 
> life and how will it work.

ah, I'm glad to share my experience here ...

the linux-vserver.org wiki shows some of those
real world usage scenarios, which include, but are
not limited to:

 - Administrative Separation
 - Service Separation
 - Enhancing Security (better chroot)
 - Easy Maintenance (hardware independance)
 - Testing

most application scenarios do not require a complete
VPS or Guest to make them usable, often only a single
* space would suffice to accomplish the goal ...

best,
Herbert

> Kirill