Updating packages in Jails

[Gary Gatten]

-----Original Message-----
From: owner-freebsd-questions at freebsd.org
[mailto:owner-freebsd-questions at freebsd.org] On Behalf Of Adam Vande
More
Sent: Monday, February 08, 2010 3:28 PM
To: Jason
Cc: Richard L. Houston; freebsd-questions at freebsd.org
Subject: Re: Updating packages in Jails

On Mon, Feb 8, 2010 at 3:15 PM, Jason <jhelfman at e-e.com> wrote:

> Use this as a starting point
>>
>> http://www.freebsd.org/doc/handbook/jails.html
>>
>> Anyways, host and jail need to run the exact same kernel.  Normally
I'll
>> build my kernel and install it into the base as well as each
individual
>> jail
>> so everything is consistent.
>>
>
> Why do they need to run the exact same kernel? I didn't see that
anywhere
> in
> the document, unless I missed it.
>
> thanks
>

They aren't a full form of visualization in terms of having a
hypervisor, as
it is dependent the system calls coming from a jail being the same calls
that are present in the host kernel.  Mismatched kernel version could
break
that mapping.  Which is also why jails are a faster form of
virtualization
because all the call mappings are 1:1.

At least that's my understanding.


Question:

Hopefully this isn't considered a hijack, but what are the *main* diffs
between jails and vm's?  I've never worked with jails but read about
them several times.  Do they allow controlling of CPU cycles, Memory
regions, etc. in the same manner as the file system(s) and network?

Asked another way, what are some Usage cases where jails would be equal
or more appropriate than full on vm's and vice-versa.  We use vm's quite
extensively and I'm wondering of some of these can be done in jails
instead.

TIA!

Gary

PS: Note - no top posting this time!





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