HEADS UP: caution required with updates using custom kernels

[Chris H]

On Fri, 24 Jun 2016 15:51:11 +0000 Brooks Davis <brooks at freebsd.org> wrote

> On Fri, Jun 24, 2016 at 06:00:19AM +0200, O. Hartmann wrote:
> > Am Thu, 23 Jun 2016 21:07:51 +0000
> > Brooks Davis <brooks at freebsd.org> schrieb:
> > 
> > > Kernel config minimalists and those running aarch64 and riscv systems
> > > will want to head this UPDATING message.
> > > 
> > > In practice, if you're fairly up to date, doing installworld before
> > > installkernel will also work (I've tested that case from ALPHA4), but is
> > > always somewhat risky.
> > > 
> > > -- Brooks
> > > 
> > > ----- Forwarded message from Brooks Davis <brooks at FreeBSD.org> -----
> > > 
> > > Date: Thu, 23 Jun 2016 21:02:05 +0000 (UTC)
> > > From: Brooks Davis <brooks at FreeBSD.org>
> > > To: src-committers at freebsd.org, svn-src-all at freebsd.org,
> > >     svn-src-head at freebsd.org
> > > Subject: svn commit: r302152 - head
> > > 
> > > Author: brooks
> > > Date: Thu Jun 23 21:02:05 2016
> > > New Revision: 302152
> > > URL: https://svnweb.freebsd.org/changeset/base/302152
> > > 
> > > Log:
> > >   Add an UPDATING entry for the pipe() -> pipe2() transition.
> > >   
> > >   Approved by:    re (gjb)
> > >   Sponsored by:    DARPA, AFRL
> > > 
> > > Modified:
> > >   head/UPDATING
> > > 
> > > Modified: head/UPDATING
> > >
> > >
=============================================================================
> > > = --- head/UPDATING    Thu Jun 23 20:59:13 2016    (r302151)
> > > +++ head/UPDATING    Thu Jun 23 21:02:05 2016    (r302152)
> > > @@ -31,6 +31,14 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 11
> > >      disable the most expensive debugging functionality run
> > >      "ln -s 'abort:false,junk:false' /etc/malloc.conf".)
> > >  
> > > +20160622:
> > > +    The the libc stub for the pipe(2) system call has been replaced with
> > > +    a wrapper which calls the pipe2(2) system call and the pipe(2) is
> > > now +    only implemented by the kernels which include "options
> > > +    FREEBSD10_COMPAT" in their config file (this is the default).
> > > +    Users should ensure that this option is enabled in their kernel
> > > +    or upgrade userspace to r302092 before upgrading their kernel.
> > > +
> > >  20160527:
> > >      CAM will now strip leading spaces from SCSI disks' serial numbers.
> > >      This will effect users who create UFS filesystems on SCSI disks
> > >      using > > 
> > > 
> > > ----- End forwarded message -----
> > 
> > Is this showing up, when one doesn't have the expected COMPAT_FREEBSD10 in
> > kernel and updated kernel __before___ world?:
> 
> You must include COMPAT_FREEBSD10 or have a new userspace.  Otherwise
> things like your shell are unlikely to work.
> 
> -- Brooks
> 
Hi. I don't see any indication of why this change was required
(the obsolescence of pipe(2))
Can you elaborate a little, please?

Thanks.

--Chris