Re: [libvirt-users] Obtaining the PID of a domain's QEMU process from C

On 3/11/19 9:02 AM, Erik Skultety wrote: > On Sat, Mar 09, 2019 at 04:32:00PM +0100, Michal Prívozník wrote: > > On 3/1/19 2:31 AM, Shawn Anastasio wrote: > > > Hello all, > > > > > > I'm currently writing a C program that uses the libvirt API and I need a > > > way to obtain the pid of a given domain's QEMU process. > > > > > > Specifically, I'm writing an ivshmem server that uses SO_PEERCRED to get > > > the pid of clients that connect to it, and I would like to use that pid > > > to look up the domain in libvirt to determine the proper domain ID to > > > return to the client. > > > > > > As far as I can tell, libvirt doesn't expose this information in an easy > > > to access manner. Of course it is possible to call `ps` and grep for the > > > information I'm looking for, but I was hoping for a cleaner solution. > > > > > > If anybody knows how to do this, advice would be greatly appreciated. > > > > There isn't an API for that as we don't want users to fiddle with qemu > > That's right, and it should stay that way. On the other hand, the same way we > can't prevent anyone from editing /etc/libvirt/qemu/<domain>.xml or > /var/run/libvirt/qemu/<domain>.xml or run the 'ps' command or whatever we might > as well report the PID as part of virConnectListAllDomains data. I don't have > a problem with reporting PIDs in principle, provided it's used for informatory > purposes. > Having said that, there's the question of why libvirt should report something > that it doesn't need to consume, IOW we report machine ID which we can use to > control the machine, we also report UUID which we can consume, but we'd do > absolutely nothing with the PID besides reporting it. > Another thing is that reporting PIDs of machines running on a remote host is > quite useless for locally running clients. Alternatively, we may do what LXC driver already does -> domain ID is PID of init running within the container. In QEMU driver, the domain ID can be PID of qemu then.