On Fri, Aug 30, 2019 at 04:39:39PM +0200, Marco Gaiarin wrote:
>
> > But, the 'code' that identify (and change permission) for journal dev
> > are PVE specific? or Ceph generic? I suppose the latter...
>
> OK, trying to identify how OSDs get initialized. If i understood well:
>
> 0) systemd unit for every OSD get created following a template:
> /lib/systemd/system/ceph-osd@.service
>
> 1) every unit call a 'prestart' script:
> ExecStartPre=/usr/lib/ceph/ceph-osd-prestart.sh --cluster ${CLUSTER} --id %i
>
> 2) The prestart script, run udev:
>
> udevadm settle --timeout=5
>
> that simply force the processing of udev queue, only to be sure
> there's some 'unhandled' device in the queue.
>
> 3) udev (rules in /lib/udev/rules.d/95-ceph-osd.rules), looking for
> GPT ID_PART_ENTRY_TYPE do two things:
>
> a)
> ceph-disk --log-stdout -v trigger /dev/$name
> (that AFAIK trigger a disk mount, for filestore)
>
> b)
> chown ceph:ceph /dev/$name; chmod 660 /dev/$name
>
>
> So, seems to me that a decent method to solve/circumvent my trouble is
> to:
>
> i) write a 'static' udev rule that chown ceph:ceph the partition. Very
> dirty.
>
> ii) modify the systemd unit and add an ExecStartPost= script that chown
> the partition. Dirty but probably effective.
>
> iii) modify /usr/lib/ceph/ceph-osd-prestart.sh to add the condition,
> something like (untested):
>
> if [ -L "$journal" -a -e "$journal" ]; then
> dev_journal=`readlink -f $journal`
> owner=`stat -c %U $dev_journal`
> if [ $owner != 'ceph' ]; then
> echo "ceph-osd(${cluster:-ceph}-$id): journal probably manually symlinked, fixing permission." 1>&2
> chown ceph: $dev_journal
> fi
> fi
>
>
> I'm not a ceph expert, but solution iii) seems decent for me, with a
> little overhead (a readlinkk and a stat for every osd start).
However you like it. But to note that in Ceph Nautilus the udev rules
aren't shipped anymore.
>
>
>
> But still i don't understood why, if i have:
>
> root@capitanmarvel:~# LANG=C id ceph
> uid=64045(ceph) gid=64045(ceph) groups=64045(ceph),6(disk)
>
> and:
> brw-rw---- 1 root disk 8, 6 ago 28 14:38 /dev/sda6
>
> (so, journal partition group-owned by 'disk' and 'ceph' user in group
> 'disk'), still i have permission access.
>
> The ceph-osd process reset group ownership on runtime?
In Luminous udev is handling all of that, see 95-ceph-osd.rules.
--
Cheers,
Alwin
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