Hi Ilya, unfortunately I can not find any "missing primary copy of ..." error in the logs of my 3 OSDs. The NVME disks are also brand new and there is not much traffic on them. The only error keyword I find are those two messages in osd.0 and osd.1 logs shown below. BTW the error posted before actually concerns osd1. The one I posted was copied from somebody elses bug report, which had similar errors. Here are my original error messages on LTSP boot: [ 10.331119] libceph: mon1 (1)10.101.0.27:6789 session established [ 10.331799] libceph: client175444 fsid b0f4a188-bd81-11ea-8849-97abe2843f29 [ 10.336866] libceph: mon0 (1)10.101.0.25:6789 session established [ 10.337598] libceph: client175444 fsid b0f4a188-bd81-11ea-8849-97abe2843f29 *[ 10.349380] libceph: get_reply osd1 tid 11 data 4164 > preallocated* *4096, skipping* elias@maas:~$ juju ssh ceph-osd/2 sudo zgrep -i error /var/log/ceph/ceph-osd.0.log 2021-05-16T08:52:56.872+0000 7f0b262c2d80 4 rocksdb: Options.error_if_exists: 0 2021-05-16T08:52:59.872+0000 7f0b262c2d80 4 rocksdb: Options.error_if_exists: 0 2021-05-16T08:53:00.884+0000 7f0b262c2d80 1 osd.0 8599 warning: got an error loading one or more classes: (1) Operation not permitted elias@maas:~$ juju ssh ceph-osd/0 sudo zgrep -i error /var/log/ceph/ceph-osd.1.log 2021-05-16T08:49:52.971+0000 7fb6aa68ed80 4 rocksdb: Options.error_if_exists: 0 2021-05-16T08:49:55.979+0000 7fb6aa68ed80 4 rocksdb: Options.error_if_exists: 0 2021-05-16T08:49:56.828+0000 7fb6aa68ed80 1 osd.1 8589 warning: got an error loading one or more classes: (1) Operation not permitted How can I find our more about this bug? It keeps coming back every two weeks and I need to restart all OSDs to make it go away for another two weeks. Can I check "tid 11 data 4164" somehow. I find no documentation, what a tid actually is and how I could perform a read test on it. Another interesting detail is, that the problem does only seem to affect booting up from this RBD but not operation per se. The thin clients already booted from this RBD continue working. All systems run: Ubuntu 20.04.2 LTS Kernel 5.8.0-53-generic ceph version 15.2.8 (bdf3eebcd22d7d0b3dd4d5501bee5bac354d5b55) octopus (stable) The cluster has been setup with Ubuntu MAAS/juju, consists of * 1 MAAS server * with 1 virtual LXD juju controller * 3 OSD servers with one 2 TB Nvme SSD each for ceph and a 256 SATA SSD for the operating system. * each OSD contains a virtualized LXD MON and an LXD FS server (setup through juju, see juju yaml file attached). How can I investigate this problem further or might an upgrade to pacific be necessary? My best regards, Markus Am Mi., 28. Apr. 2021 um 19:25 Uhr schrieb Ilya Dryomov <idryomov(a)gmail.com

Am So., 16. Mai 2021 um 15:36 Uhr schrieb Ilya Dryomov <idryomov(a)gmail.com>om>: Sorry, I was not aware of that. elias@maas:~$ rbd info squashfs/ltsp-01 rbd image 'ltsp-01': size 3.5 GiB in 896 objects order 22 (4 MiB objects) snapshot_count: 0 id: 23faade1714 block_name_prefix: rbd_data.23faade1714 format: 2 features: layering, exclusive-lock, object-map, fast-diff, deep-flatten op_features: flags: create_timestamp: Mon Jan 11 12:09:22 2021 access_timestamp: Wed Feb 24 10:55:17 2021 modify_timestamp: Mon Jan 11 12:09:22 2021 I don't have the boot log available right now, but you can watch a video of the boot process right here: https://photos.app.goo.gl/S8PssYu2VAr4CSeg7 It seems to be consistently "tid 11" consistently, while in this video it was "data 4288" not "data 4164" as above. But the image has been modified in the meantime, as far as I can recall, so that might be due to that reason. I did reboot all OSD nodes and since the MON and FS nodes run as LXD/juju instances on them, they were rebooted as well. Currently "squashfs/ltsp-01" is mapped on 4 nodes. As the pool name indicates, the FS was converted to squashfs and is therefore mounted read-only, while the underlying dev might actually not be mounted read-only, as there does not seem to be an option available to mount RO via /sys/bus/rbd/add_single_major or /sys/bus/rbd/add. As far as I can tell, the only way to force RO is to map a snapshot instead. Currently, there are only 4 active clients but the system is intended to being able to sustain 100s of clients. We are using an RBD as boot device for PXE booted thin clients, you might have heard of the Linux Terminal Server Project (ltsp.org). We adapted the stack to support booting from RBD. The clients do not write to the FS/dev, all necessary write operations happen on a mapped overlayfs. Currently we have one virtual machine with an ext4 FS on RBD "rbd/ltsp-01", where we prepare the boot images for LTSP. We generate a squashfs from that FS and then dd it onto a RBD "squashfs/ltsp-01" and back up the previous version by moving it to another RBD name. The initrd mapping process can be reviewed here: https://github.com/trickkiste/ltsp/blob/feature-boot_method-rbd/debian/ltsp… Does the affected image serve as a golden image? Or some other image is snapshotted and cloned from before booting? The same RBD is mapped by all clients and the squashfs image on it is mounted read-only. > What do clients do after they boot? Normal desktop operation, they serve as fat clients with the RBD as their distributed network boot drive. As said above, all write access is done to an overlayfs ramdisk. > Thanks, > Ilya Thank you for reviewing this issue. My best regards Markus

Am So., 16. Mai 2021 um 19:38 Uhr schrieb Ilya Dryomov <idryomov(a)gmail.com>om>: Yes. Line 110 https://github.com/trickkiste/ltsp/blob/feature-boot_method-rbd/debian/ltsp… echo "${mons} name=${user},secret=${key} ${pool} ${image} ${snap}" > ${rbd_bus} No, just 4. Most of the time 3 still running and working correctly and one stuck at reboot. Maybe the sum of all LTSP client reboots since I cleared the problem by rebooting the OSDs could amount to 60-70. I do not know, as we are not logging that currently. OK, currently I am seeing 5, which is one more than the number of clients we have. So it seems these watchers do not timeout after reboot or hard reset. Is there any way to make these watchers time out? Thank you, we will add this missing piece to our rbd initrd code. Are you a ceph dev? Could you make sure to add this to kernel documentation too! https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-bus-rbd There is no mention of that option currently. I might even have tried this but it might not have worked. Not sure, this has been over a year back. Also missing in the documentation is, how one could mount a CephFS on boot!!! We are thinking about switching to booting a CephFS in the future. But I would not have any idea and did not find any documentation on how we would approach that - which boot kernel option to use, which sysfs interface could be used, or which tools we must include in initrd. Generally it would be great if you could include the proper initrd code for RBD and CephFS root filesystems to the Ceph project. You can happily use my code as a starting point. https://github.com/trickkiste/ltsp/blob/feature-boot_method-rbd/debian/ltsp… My best regards Markus

Am So., 16. Mai 2021 um 21:36 Uhr schrieb Ilya Dryomov <idryomov(a)gmail.com>om>: Not really, I see 3 watchers for one of my client IPs right now and one for each of the others. Have to investigate further. The clients are assigned the same IP on each bootup, so shouldn't the watchers either time out or be "claimed/taken over" by the newly booted client? I will investigate, if it is only one client, producing all the watchers until the limit is reached, or if all clients produce this problem together and then report back on the issue. Thanks for the tip! However, I would argue that these krbd options should either be available in the kernel documentation as well, or at least this man page should be mentioned in the kernel documentation. Yes, CephFS as a roof filesystem. The reason, why this would be convenient is, that we could then have one VM or client mounted this CephFS in RW mode, therefore being able to make updates to the packages installed etc. while the other clients would be restricted to read-only rights via authx. We would still be able to create snapshots of the last properly working OS configuration but without the additional hassle. Also, if we do OS package upgrades, these upgrades would be instantly available on the clients as well without the need to reboot, since due to the network-fs nature of CephFS all clients would be aware of the underlying changes to the FS. be sufficient. The actual mapping and mounting in both NFS and RBD does take place in the initrd scripts. The RBD initrd script actually is derived from the NFS initrd script, so I would presume that one could make CephFS mount work in a similar fashion. Question being, which tools are needed to make this work? I guess "mount" provides everything needed already, does it not? Thank you so much for you support, Markus Thanks,

Hi Nico, we are already doing exactly that: Loading initrd via iPXE which contains the necessary modules and scripts to boot an RBD boot dev. Works just fine. And Ilya just helped to work out the last show stopper, thanks again for that! We are using a modified LTSP system for this. We have proposed some patches to LTSP to get the necessary facilities upstream but Alkis Georgopoulos first want to see that there is enough interest for that before he considers merging our patch or creating the necessary changes himself. However the necessary initrd code is already available in this merge request: https://github.com/trickkiste/ltsp/blob/feature-boot_method-rbd/debian/ltsp… I see you are from Switzerland - neighbors! Out of interest, what are you planning to use this for? Servers, Thin/Fat Clients? My best regards Markus Am So., 16. Mai 2021 um 23:18 Uhr schrieb Nico Schottelius < nico.schottelius(a)ungleich.ch&gt;gt;:

Am Mo., 17. Mai 2021 um 20:28 Uhr schrieb Nico Schottelius < nico.schottelius(a)ungleich.ch&gt;gt;: The way it works in LTSP is, that you run a script provided by the ltsp project, which copies the kernel to your tftpboot directory and sets the ipxe boot options accordingly. Currently there is no automatism for mapping and mounting the RBD for this purpose, you have to map it by hand and mount it to the proper dir prior to running the script. I am sure you can integrate this into your workflow by using what is currently in ltsp and my rbd branch as an example. In Vienna? Not been there for ages but happy to meet. Alright, I understand. Yes, your scenario would work, while you would only need to borrow the ipxe stuff from LTSP and my rbd initramfs-hook and initramfs-script. The initramfs stuff should actually be molded into a separate Ubuntu package and made available to upstream. The mapping RO stuff, which Ilya has provided yet needs to be added and all the other available kernel options should be made available as well. My best regards Markus