Date: Sun, 29 Apr 2018 12:34:06 -0600 From: Warner Losh <imp@bsdimp.com> To: Jan Knepper <jan@digitaldaemon.com> Cc: Willem Jan Withagen <wjw@digiware.nl>, Alan Somers <asomers@freebsd.org>, FreeBSD Filesystems <freebsd-fs@freebsd.org>, FreeBSD Hackers <freebsd-hackers@freebsd.org>, Richard Yao <ryao@gentoo.org> Subject: Re: Getting ZFS pools back. Message-ID: <CANCZdfqWKZpCfnB0OZ_OkOMAzwbtBEOU%2B2EXGQ9VgP6yUq6kZg@mail.gmail.com> In-Reply-To: <5692d3b6-038e-4c4b-c5b6-b0f719b4ac38@digitaldaemon.com> References: <5f836c79-b379-f066-689b-1645e393c5e9@digiware.nl> <E3B39DFA-269A-4041-922E-38F0CF35CB9A@gentoo.org> <a7fb7ffc-fa5f-4031-c78a-20e7ba618566@digiware.nl> <CAOtMX2gpuc0ntoxqKJv3iw3x_Dcq99zpcmqE8g%2B2QiDtYPHmZQ@mail.gmail.com> <1645b168-4133-693c-2dd3-8e0606abb9c3@digiware.nl> <07576f68-f67e-3a22-7a50-ff261c9b3fff@digitaldaemon.com> <CANCZdfonKRcFKiV%2BCmCvAQ3O5h%2BuNBcWDW7oyxOhWMdmpDHEcw@mail.gmail.com> <5692d3b6-038e-4c4b-c5b6-b0f719b4ac38@digitaldaemon.com>
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On Sun, Apr 29, 2018 at 12:31 PM, Jan Knepper <jan@digitaldaemon.com> wrote: > However, most 11.x binaries work well enough to at least bootstrap / fix > problems if booted on a 10.x kernel due to targeted forward compatibility. > You shouldn't count on it for long, but it generally won't totally brick > your box. In the past, and I believe this is still true, they work well > enough to compile and install a new kernel after pulling sources. The 10.x > -> 11.x syscall changes are such that you should be fine. At least if you > are on UFS. > > However, the ZFS ioctls and such are in the bag of 'don't specifically > guarantee and also they change a lot' so that may be why you can't mount > ZFS by UUID. I've not checked to see if there's specifically an issue here > or not. The ZFS ABI is somewhat more fragile than other parts of the > system, so you may have issues here. > > If all else fails, you may be able to PXE boot an 11 kernel, or boot off a > USB memstick image to install a kernel. > > Generally, while we don't guarantee forward compatibility (running newer > binaries on older kernels), we've generally built enough forward compat so > that things work well enough to complete the upgrade. That's why you > haven't hit an issue in 18 years of upgrading. However, the velocity of > syscall additions has increased, and we've gone from fairly stable (stale?) > ABIs for UFS to a more dynamic one for ZFS where backwards compat is a bit > of a crap shoot and forward compat isn't really there at all. That's likely > why you've hit a speed bump here. > > I have not closely looked at the procedures outlined in /usr/src/UPDATING > for 11.x. But do I read correctly that performing a buildworld, > buildkernel, then installworld and reboot to update from 10.4 to 11.x does > not work? > No. That will work. If you always install a new kernel and reboot (especially across major releases) and then install the new binaries, you're safe. You won't get into a situation where new binaries are running on an old kernel. As far as I know that's not broken, even with the strange ABI issues I talk about. That's only when you're running 11.x binaries on a 10.x kernel, not the other way around. Warner
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