On 09/09/2015 11:40 AM, George Dunlap wrote:
On Tue, Sep 8, 2015 at 11:25 PM, T.Weyergraf <T.Weyergraf@xxxxxxxxxxxxx> wrote:
Hi
I gave the new Xen-4.6rc2 a spin on a CentOS 7 virtualisation guest
(nested-xen). I haven't yet started testing guests, but rather looked at the
install itself.
One issue, I found, was with xenstored.service and the corresponding
unit-file:
[root@xencen7ws ~]# systemctl status xenstored
xenstored.service - The Xen xenstore
Loaded: loaded (/usr/lib/systemd/system/xenstored.service; disabled)
Active: active (running) since Tue 2015-09-08 23:13:43 CEST; 13min ago
Process: 757 ExecStartPre=/bin/mkdir -p /var/run/xen (code=exited,
status=0/SUCCESS)
Process: 753 ExecStartPre=/bin/rm -f /var/lib/xenstored/tdb* (code=exited,
status=0/SUCCESS)
Process: 740 ExecStartPre=/bin/grep -q control_d /proc/xen/capabilities
(code=exited, status=0/SUCCESS)
Main PID: 760 (xenstored)
CGroup: /system.slice/xenstored.service
└─760 /usr/sbin/xenstored
Sep 08 23:13:43 xencen7ws.virtfinity.local xenstored[760]: TDB: tdb_open_ex:
could not open file /var/lib/xenstored/tdb: No such file or directory
Sep 08 23:13:43 xencen7ws.virtfinity.local xenstored[760]: Checking store
...
Sep 08 23:13:43 xencen7ws.virtfinity.local xenstored[760]: Checking store
complete.
Sep 08 23:13:43 xencen7ws.virtfinity.local xenstored[760]: xenstored is
ready
Sep 08 23:13:43 xencen7ws.virtfinity.local systemd[1]: Started The Xen
xenstore.
As you can see, xenstored.service is running, but disabled by the package
installation. This is, because xenstored.service apparently got overseen in
the source-rpm's spec-file's post runtime/preun runtime. See diff [1] for
details.
The Xen documentation (in INSTALL) recommends enabing
xen-init-dom0.service, xenconsoled.service, and
xen-qemu-dom0-disk-backend.service. I didn't specifically enable
xenstored, because I figured that was the "systemd way" -- specify the
dependencies, specify what you actually want (i.e., a xen dom0), and
let it sort out what actually needs to be started.
Is there a good reason to specifically enable xenstored, even though
it will start automatically because of dependencies?
(I really am asking here -- this whole systemd thing is really new to me.)
If the Xen docs (which I haven't checked) state it should not be
enabled, it's probably best to follow that advice. xenstored is a bit
tricky, as it's not designed to be started/stopped or restarted as a
regular service.
For my initial report, I checked the stuff I recycled from fedora, which
indeed enables xenstored.service and uses a pidfile. From an
administrative point of view, I like pidfiles, as they allow to check a
service from a script with very little effort. xenstored-pidfiles have
been present all the time except until lately (apparently) and I dislike
changing things like that without good reason.
Suffice to say, that there might be a good reason.
I found the initial systemd-related patches to Xen, adding the unit
files, but I still need to find the patches changing that behaviour and
explaining the reasons.
Also, I think xenstored should write a pidfile. You might consider adding to
/usr/lib/systemd/system/xenstored.service:
PIDFile=/var/run/xenstored.pid
and change
ExecStart=/usr/sbin/xenstored
to
ExecStart=/usr/sbin/xenstored --pid-file /var/run/xenstored.pid
$XENSTORED_ARGS
Hope this helps, this is just a quick start. I'll continue checking and
reporting during the next days.
I think because systemd doesn't do forking, that it doesn't need a
pidfile. In fact, if xenstored detects that it's running under
systemd, it will actually ignore the --pid-file directive.
A quick check shows xenstored for systemd to create the socket (in the
systemd case). I will read up more code and patches.
For the time being, you are right. Let's not change, what appears to be
there for a reason. Once up and running, your packages provide a working
xenstored, so there is nothing "broken" by any means.
-George
Regards,
Thomas
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