Re: [Vserver] Create a guest

From: Herbert Poetzl <herbert_at_13thfloor.at>
Date: Wed 29 Mar 2006 - 15:39:24 BST
Message-ID: <20060329143924.GA15842@MAIL.13thfloor.at>

On Wed, Mar 29, 2006 at 04:14:11PM +0200, Albert Shih wrote:
> Hi all
>
> Maybe very stupid question, but have a server running FC4 with
> vserver-patch kernel.
>
> I want launch two guest with same version of linux but I don't want
> make a big copy. How can I do that ?

that really depends on the requirements, basically
you have (at least) the following options:

 - just share the same dirs for several guests
   (requires that they are well behaved and do not
   modify/depend on the same file)

 - have 95% of the guest readonly/immutable and
   share that via mount or overlayfs between them
   (works if you do not want to update one of them
   at a later point in time)

 - use unification with or withoout CoW link
   breaking to get roughly the same effect without
   using hardlinks
   (works even with potentially hostile guests)

> I suppose I can do that with hard link (I've seen this somewhere in
> google), but hard link don't work with directory. Is the only solution
> is make lots of hardlink ?

yes, lots of 'special' hardlinks basically, but
don't worry, there are tools which create them
for you, similar to cp -la ...

> Where can I find a documentation for make guest with hard-link ?

vunify and vhashif will do that for you (note:
they will not unfiy with the host fs)

http://linux-vserver.org/alpha+util-vserver
(check the Directory/vserver unification section)

> (or any solution to make two guest identical to the host and
> without on samll disk).

well the 'identical' to host is a slightly different
issue, as it is not really advised to mix host with
guests, usually you have several guests who share the
same files, but with CoW link breaking or via RO
mounts this should be doable too ...

HTH,
Herbert

> Lots of thanks.
>
> --
> Albert SHIH
> Universite de Paris 7 (Denis DIDEROT)
> U.F.R. de Mathematiques.
> 7 ième étage, plateau D, bureau 10
> Heure local/Local time:
> Wed Mar 29 16:10:00 CEST 2006
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