Hello,
I have tested both methods to install a kernel again. I have copied my before created and saved 10.3 kernel to /boot/kernel, which was acutal a 11.0 kernel. Then, first, I do a freebsd-update in expectation to get a full standard kernel with debug symbols - because for 11.0 it is written that this is the default:
and installed it - but in /usr/lib/debug/boot/kernel are no symbol files ???
Also the kernel have just 107 MB and 818 files - is this a full kernel?
I copied this kernel form /boot/kernel to /boot/GENERIC. Then, second, I fetched the sources:
I had created before the file /etc/src.conf. And in this file I write some options, like
After

This is total reverse I had read about it. What could here be wrong?
Here is my src.conf file. Have I do some misstakes? Is there something written wrong?
I have tested both methods to install a kernel again. I have copied my before created and saved 10.3 kernel to /boot/kernel, which was acutal a 11.0 kernel. Then, first, I do a freebsd-update in expectation to get a full standard kernel with debug symbols - because for 11.0 it is written that this is the default:
freebsd-update --currently-running 10.3-RELEASE -r 11.0-RELEASE upgrade
and installed it - but in /usr/lib/debug/boot/kernel are no symbol files ???

Also the kernel have just 107 MB and 818 files - is this a full kernel?
I copied this kernel form /boot/kernel to /boot/GENERIC. Then, second, I fetched the sources:
svn checkout svn://svn.freebsd.org/base/release/11.0.1 /usr/src
and do buld a "customized kernel" that should be used /etc/src.conf: make buildkernel
make installkernel
I had created before the file /etc/src.conf. And in this file I write some options, like
Code:
#
# /etc/src.conf (default location)
#
# --source build options
# --for *make buildworld* *make buildkernel*
# src.conf is to set make(1) variables that control the aspects
# of how the system builds. It uses the standard makefile syntax.
WITHOUT_DEBUG_FILES=yes
After
make installkernel
has finished I take a look into /usr/lib/debug/boot/kernel and expected that there are no debug symbol files of the kernel, because of the option in src.conf I had given. But know all debug symbols for the kernel has been build ??? 
This is total reverse I had read about it. What could here be wrong?

Here is my src.conf file. Have I do some misstakes? Is there something written wrong?
Code:
#HL-170131 (vServer-hetzner.de)
# *****************************************************************************
#
# /etc/src.conf (default location)
#
# --source build options
# --for *make buildworld* *make buildkernel*
# src.conf is to set make(1) variables that control the aspects
# of how the system builds. It uses the standard makefile syntax.
#
# src.conf should not specify any dependencies to make(1)
# it only affects buildings FreeBSD not ports or packages
#
# see >man 8 src.conf
# *****************************************************************************
# *****************************************************************************
#HL-170127 added for FreeBSD 11.0 running on vServer
# *****************************************************************************
WITHOUT_DEBUG_FILES=yes
WITHOUT_FLOPPY=yes
WITHOUT_GAMES=yes
WITHOUT_HTML=yes # Set to not build HTML docs.
WITHOUT_SENDMAIL=yes # not build sendmail(8) and related programs.
WITHOUT_TALK=yes # The talk utility is a visual communication program
# which copies lines from your terminal to that of another user.
WITH_TESTS=yes # To install the FreeBSD Test Suite in /usr/tests
#WITHOUT_USB=yes # virtual Server outside, but USB need by others
WITHOUT_BLUETOOTH=yes
WITHOUT_WIRELESS=yes # virtual Server outside
WITHOUT_WIRELESS_SUPPORT=yes
#WITHOUT_ZFS=yes