On Friday, March 22, 2019, 12:36:16 PM CDT, Peter Krempa
<pkrempa(a)redhat.com> wrote:
On Wed, Mar 20, 2019 at 15:48:43 -0500, Eric Blake wrote:
> On 3/20/19 1:50 PM, Mircea Husz wrote:
> > I scripted the creation of snapshots and it works fine. Now I'd like to run
the script as non-root.
> >
> > virsh snapshot-create-as --domain hq-live-v01 \
> > --name snappy \
> > --diskspec
vda,file=/var/lib/libvirt/images/hq-live-v01.snappy,snapshot=external \
> > --diskspec
vdb,file=/var/lib/libvirt/images/hq-live-storage.snappy,snapshot=external \
> > --disk-only --quiesce --atomic
> >
> > This fragment creates the snapshots, but get created with mode 0600:
> > -rw------- 1 qemu qemu 393216 Mar 19 17:08 hq-live-storage.snappy
> > -rw------- 1 qemu qemu 1048576 Mar 19 17:08 hq-live-v01.snappy
> >
> > The user account is in the libvirt group and has permissions to do everything
except delete the files created by the snapshot, all I need is to get the snapshots
created with 0660 mode.
> >
> > This is on a Centos 7.6 installation. What knobs do I need to turn to control
the umask?
>
> I'm not sure if you can force libvirt to create the files with a
> different mask, but perhaps a workaround would be to pre-create the
> files yourself with desired permissions, then tell virsh to
> --reuse-external (so that libvirt no longer has to try and create the
> files, and thus doesn't mess with permissions).
--reuse-external is good only for using a custom-formatted image.
Libvirt will chown the image to qemu:qemu if you don't disable
relabelling. This is possible to do via the <seclabel> even in a
snapshot <disk> definition.
I created an image as the non-root user and it worked well.
qemu-img create -f qcow2 /path/to/file 1k
Note that it's not documented yet and also does not conform to
the
schema, but the parser happily parses it and the code uses the correct
<seclabel> then. I have a not-sufficiently-tested patch that adds the
schema (and IIRC also docs) which I planned to send after testing.
Yes, I noticed that the snapshot changed the owner back to qemu.
I just added the user to the qemu group. Good thing it didn't change the mask.
Also, selinux is disabled on this installation.
Thank you for the helpful information.
-Mike