So, here's the skinny. Lots of background, but I have a series of scripts. One starts/stops a single qemu instance, and another calls that to start/stop all VMs.
The "all start/stop VMs" script is used on boot or shutdown, called by an init script, and the single script does a variety of things -- like send ACPI shutdown, waiting, etc, etc. Anyhow when scripting these things, I noticed this behaviour in qemu if I attempt to start a running qemu: $ kvm <lots of command line args plus..> -pid pidfile.pid Could not acquire pid file: Resource temporarily unavailable So, I skipped past the "check if qemu" is running phase, and left the job of not starting a running VM to qemu. It should, after all, be best at this. (This was my thought process.) However whenever qemu starts it opens / overwrites the socket, THEN sees the PID file is locked, then closes the socket + exits. And, you are then left with a running qemu which has no usable socket any more. The bare metal layer servers we're using, have both production and development VM instances. And, those development instances do get stopped and started much more often. Meaning, it is often convenient to stop individual dev VMs one at a time, but start them all back up at once. And then the next day, or next week I'd notice the qmp socket was MIA. So, there's my story. I hope you enjoyed it. I'll be at the concierge's office while the police arrive. On Fri, 28 Oct 2016 17:53:00 +0300 Michael Tokarev <m...@tls.msk.ru> wrote: > Control: tag -1 moreinfo unreproducible > > 28.10.2016 17:30, Brad Barnett wrote: > > Package: qemu-system-x86 > > Version: 1:2.1+dfsg-12+deb8u6 > > > > I've been unable to find anything about this via Google searches, > > mailing list searches, IRC, you name it. Nor, does the documentation > > seem to indicate I'm doing anything wrong. > > > > Additional queries to qemu-devel and qemu-discuss fell flat, with zero > > replies. > > > > I'm starting qemu with various options, including this: > > > > -qmp unix:/path_to_sock_dir/box.uniquename.sock,server,nowait > > > > I'm using socat to connect: > > > > socat UNIX-CONNECT:/path_to_sock_dir/box.uniquename.sock STDIO > [] > > What happens is that randomly, socat can no longer connect to the > > socket in question. This has happened after successful uses of that > > very socket, and also if I've never used that socket before. > > So, when socat isn't able to connect anymore, what does > > lsof /path_to_sock_dir/box.uniquename.sock > > says about it? Does the socket exist at all? > > There's no code in qemu to remove the socket or to mess with it in > any other way during runtime, and has never been. > > The same code is used for all other unix sockets too, be it > monitor (hmp), vnc or other things. > > If the socket is being deleted or moved, it is done outside > qemu. For example, you can use mv(1) or rm(1) tool to do so, > and socat will return exactly the error you mentioned above. > > If you try to start another qemu with the same socket, that > socket will be overridden too. > > If you exit qemu listening on that socket, the socket will > refuse connections as well. > > I myself used various sokets in qemu, including qmp, countless > number of times, and right now all my VMs run with qmp unix > socket enabled. Libvirt, the main qemu management interface, > uses it too. > > So I'm really unsure what's going on here. It looks like > something specific to your environment, please check the > above variants. > > Thanks, > > /mjt
