TimeMachine support for Big Sur - missing F_FULLFSYNC?

[Andrew Walker]

On Thu, Mar 4, 2021 at 9:21 AM Tom Talpey via samba-technical <
samba-technical at lists.samba.org> wrote:

> Just a quick update to say that after an upgrade to Samba 4.11,
> as expected Time Machine is working fine from Big Sur. It's
> quite simple to configure, in fact - most everything flows
> from minimal added settings in smb.conf:
>
>   [global]
>     ...
>     vfs objects = fruit streams_xattr
>
>   [TimeMachine]
>     ...
>     fruit:time machine = yes
>
> mDNS doesn't appear to be functioning for some reason, so
> I've hotwired avahi-daemon to advertise the share.
>
> There are some quirks due to my use of a ZFS backend, and
> the usual set of Ubuntu package mix-and-match differences,
> which is why I'm only on 4.11 for now. I'm sorting out the
> fruit:metadata, fruit:resource and fruit:nfs_aces options
> relative to ZFS, but Time Machine appears to be not so
> sensitive to these. One thing at a time.
>
> I'll try to add something useful to the wiki later.
>
> Tom.
>
> On 3/2/2021 8:14 AM, Tom Talpey via samba-technical wrote:
> > On 3/2/2021 1:56 AM, Ralph Boehme wrote:
> >> Hi Tom!
> >>
> >> Am 3/2/21 um 4:51 AM schrieb Tom Talpey via samba-technical:
> >>> Does the 4.7.6 version of vfs_fruit support F_FULLFSYNC advertisement?
> >>> I find some mentions of earlier versions supporting F_FULLSYNC (no
> extra
> >>> "F"!), but zero mention of either fullsync or fullfsync in release
> notes
> >>> for any Samba/vfs_fruit version. Is that just a typo, in which case,
> why
> >>> is Big Sur complaining?
> >>
> >> You need at least 4.8 for this.
> >
> > Hi Ralph! I guess I figured Ubuntu would be off-by-one. :)
> > I'll upgrade, had hoped to avoid a full network forklift but
> > it's perhaps due.
> >
> > I think it would be good to refresh the wiki regarding this.
> > I did find
> >
> >
> https://wiki.samba.org/index.php/Configure_Samba_to_Work_Better_with_Mac_OS_X
> >
> > which does in fact state the 4.8 requirement in rather fine
> > print, but the page says things like "here are suggestions"
> > to "improve operability with Mac OS X", and "as far as I know".
> > I'll see if I can help improve it after I muddle through the
> > situation.
> >
> > Tom.
>
> ZFS in general doesn't have an upper-limit on size of xattrs that can be
written, but Linux kernel puts cap at 64 KiB for max xattr size.
ZFS on FreeBSD allows xattrs up to size_t bytes, but due to API limitations
(no pwrite for xattrs) you don't really want to go too crazy. I once tried
to write a 30 GiB alternate datastream to a samba share on FreeBSD and was
not satisfied with the result.
Most of stuff written about NFSv4 ACLs on ZFS don't apply to general Linux
case (acltype is POSIX there).
One ZFS dataset property that is particularly useful for Samba shares
performance-wise (for reading / writing xattrs) is xattr=sa. This attribute
is available in Linux, the FreeBSD port of zfs on linux, and base FreeBSD
IIRC in 13.