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Re: Safety of upgrading packages while running KVM

On 17/06/15 09:42 PM, Ross Boylan wrote:

My host system is running Debian wheezy and qemu-kvm; a number of VM's
are running on it. I'm running kvm via libvirt.

An update to qemu-kvm and related packages is available for my host
system.  Is it safe to update the package on the host while the VM's
are running?   Similarly, is it safe to update the kernel or other
critical host components like libc while the VM's are running?

On the one hand, I think Debian is designed so updating packages on a
live system is safe.   On the other hand, doing so seems like asking
for trouble in this case, and I have read that after a kernel update a
reboot as soon as practical is advised.

Thanks.
Ross Boylan
It's generally safe to upgrade the packages. The new ones won't be brought into play until the VM is restarted.
The advice about reboots is good because until the kernel or service is restarted, you are using the old kernel while new packages might have been compiled for a newer kernel or service. Some services will be restarted by the package installation (e.g. cups) but unless they need a kernel service that has changed, it's still safe to carry on.
The bigger issue is if vulnerabilities were closed by the new kernel or service. Not restarting leaves your machine vulnerable.
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