Re: [RFC] Unify KVM kernel-space and user-space code into a single project

Antoine Martin
2010-03-22T12:06:04Z

[snip]
>>> I believe that -kernel use will be rare, though. It's a lot
>>> easier to keep everything in one filesystem.
>> Well, for what it's worth, I rarely ever use anything else. My
>> virtual disks are raw so I can loop mount them easily, and I can also
>> switch my guest kernels from outside... without ever needing to mount
>> those disks.
>
> Curious, what do you use them for?
Various things, here is one use case which I think is under-used:
read-only virtual disks with just one network application on them (no
runlevels, sshd, user accounts, etc), a hell of a lot easier to maintain
and secure than a full blown distro. Want a new kernel? boot a new VM
and swap it for the old one with zero downtime (if your network app
supports this sort of hot-swap - which a lot of cluster apps do)

Another reason for wanting to keep the kernel outside is to limit the
potential points of failure: remove the partition table, remove the
bootloader, remove even the ramdisk. Also makes it easier to switch to
another solution (say UML) or another disk driver (as someone mentioned
previously).
In virtualized environments I often prefer to remove the ability to load
kernel modules too, for obvious reasons.

Hope this helps.

Antoine