[Pkg-zfsonlinux-devel] Bug#595790: hostid: useless unless fixed

[Richard Laager]

On 09/29/2016 05:19 AM, Michael Stone wrote:
> On Wed, Sep 28, 2016 at 09:03:38PM -0700, Richard Laager wrote:
>> Getting back to ZFS and /etc/hostid... I would think that a
>> randomly-generated /etc/hostid is probably sufficient. Whether that's
>> done in the libc, spl, or zfs package makes no difference to me.
> 
> You still haven't explained why zfs doesn't just generate a uuid itself.
>
> There's a large body of work ensuring reasonable uniqueness for uuids,
> and there isn't a clear benefit to clinging to getuid.

It can't be a full UUID. The on-disk format of ZFS uses a 32-bit
integer. It doesn't really matter what we use to derive it, but a 32-bit
integer is the constraint.

For example, if you want to use the low 32-bits of /etc/machine-id, that
would work too. It'd mean carrying a patch on Debian, but if the pain of
a patch and different behavior is less than the benefits of the change,
go for it.

> Even on solaris
> there's a big honkin' warning on the man page that it isn't guaranteed
> to be unique (IIRC, getuid on containers reflects the hardware the
> container is running on).

On Solaris the zone (container) wouldn't import the pool. Pools are
imported in the "global zone". So this isn't a problem.

-- 
Richard