mergemaster failing with read-only /usr/src

[Wolfgang Zenker]

* Jilles Tjoelker <jilles at stack.nl> [150503 14:53]:
> On Sun, May 03, 2015 at 02:03:49PM +0200, Wolfgang Zenker wrote:
>> I'm trying to update this system:
>> FreeBSD pomona 11.0-CURRENT FreeBSD 11.0-CURRENT #0: Mon Apr 13 03:48:04 CEST 2015     wolfgang at pomona:/usr/obj/usr/src/sys/UBQTERL  mips

>> Source for that was probably from about April 11th. I sucessfully built
>> world and kernel, ran mergemaster -p and make installworld on rev 282299
>> but then mergemaster fails with:

>> # mergemaster -iFU

>> *** Creating the temporary root environment in /var/tmp/temproot
>>  *** /var/tmp/temproot ready for use
>>  *** Creating and populating directory structure in /var/tmp/temproot

>> /bin/sh: cannot create routing_test.tmp: Read-only file system

>>   *** FATAL ERROR: Cannot 'cd' to /usr/src and install files to
>>       the temproot environment

>> Filesystems are mounted like this:
>> # mount
>> /dev/da0s2a on / (ufs, local, noatime)
>> devfs on /dev (devfs, local, multilabel)
>> /dev/da0s1 on /boot (msdosfs, local)
>> vulcan.lyx:/usr/src11 on /usr/src (nfs, read-only)
>> vulcan.lyx:/var/obj/11/mips64 on /usr/obj (nfs)

>> This used to work before. Any ideas, any further info I could provide?

> This broke after a test was added for etc/rc.d/. Without special code,
> this causes these tests to be built and installed as part of
> mergemaster/etcmerge, like other parts of etc.

> As a workaround you can do:
>   echo make -C etc obj all | make buildenv
> on the build machine after make buildworld. Then mergemaster will work,
> even with a read-only /usr/obj.

Well, I do build on that machine directly, and /usr/obj is mounted r/w,
only /usr/src is a read-only mount. Trying the workaround on the machine
istself does not help, unfortunately: while the "make buildenv" does
work without a problem, mergemaster still fails in the same way.

Wolfgang