On Debian sid, I have ye olde and trustey 4.19 kernel, as well as the packages linux-image-amd64 and linux-image-rt-amd64.
When (re)installing zfs-dkms, e.g. on an apt upgrade, first the 4.19 modules are successfully rebuilt, then the 5.4.0-4-rt-amd64 modules exit with an error (I'm guessing zfs is not (yet?) supported on linux-image-rt), and that's the end of the zfs-dkms builds - no attempt is made to build 5.4.0-4-amd64 (plain, not -rt). This is of course shoehorns the briefly humbled end user back into booting on 4.19. Interestingly, apt install linux-image-amd64 appears to has the same/similar problem. More interestingly, and rather frustratingly, apt remove linux-image-rt-amd64 then seemed to try to rebuild zfs-dkms, balking (of course) on 5.4.0-4-rt-amd64, and thereby failing to uninstall linux-image-rt-amd64. This latter problem was swiftly dealt with with the following: apt purge linux-image-5.4.0-4-rt-amd64 linux-headers-5.4.0-4-rt-amd64 Interestingly, apt, as part of this purge command, also then removed and rebuilt (once again, uh, the delays!) 4.19.0-5-amd64 (once again successfully), and finally, successfully, built zfs modules for 5.4.0-4-amd64 (pending final reboot test yet to do of course). Should I file a bug against zfs-dkms saying something like "fails to recognize that -rt kernel is not supported (yet) by zfs, and therefore fails to skip over zfs -rt module build, therefore stops any -rt kernel from being installed at the same time" ?? Word for the wise - until further notice from the devs of zfs support for linux-image-rt, avoid mixing these two. Question: Anyone successfully hibernating with live (mounted) zfs volumes?
