Hi Tim,

What you want to do is feasible, but require good planning.

For an example, you can share RO the /usr filesystem.  When you apply a
patch on the main system which owns the disk in RW, your other machines ARE
NOT aware of the changes until you re-mount the filesystem on each Linux
machine.

You will need to carefully watch changes with some program like Tripwire to
know specifically which file were changed outside of the shared filesystem
(config file, doc, etc).  Most of the times, it will be non-critical files.

Some patches are trickier to apply that way, for example the kernel
patches.  Only some files in /usr/src are applied in the /usr filesystem
when you update the kernel, so you will need to patch every machine.
Anyway, you need to mkinitrd and zipl after installing a new kernel, which
is automatically done by the rpm scripts.

So, Tripwire and rpm -ql "package-name" are your friends to achieve this.

I hope this helps a little.

Regards.


On 7/27/06, MOEUR TIM C <[EMAIL PROTECTED]> wrote:

Hello List,

I'm pursuing an architecture for multiple guests under VM and I'd like
to know if anyone else has done the same, or if this is just an accident
waiting to happen.  I invite your thoughts, comments, and witty remarks.

Here's what I'm considering:  I'd like to create multiple VM  Linux
guests that each have read access to a set of common minidisks.  On
those common minidisks will be what I'm calling the shared Linux file
systems, such as stuff in /sbin, /bin, /boot, /lib.   Each VM Linux
guest will also have an exclusive minidisk (WRITE) that will contain the
file systems needed to update and operate (/etc, /proc, /sys, /tmp and
so on).  The assumption is that each Linux guest will use the same level
of OS, patches, and add-on programs.

I have two goals with this idea -

1) to limit maintenance procedures.   I'd only have to apply patches to
one image and all of the Linux guests would be affected.
2) conserve DASD.

I can think of several good reasons not to do this:

1) Each Linux guest will probably need to run with the largest
allocation of memory.
2) I'd likely have to shut down ALL guests in order to apply
maintenance, since updating executables on the fly (from some other
maintenance system)  would probably invite abnormal results.

I haven't experimented or detailed the specifics of what directories are
shared and which are exclusive, but I wanted to first pose the question
to this group to see if this is a good way to invite a system crash
across all of my production Linux servers.

Tim



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