X11 for macOS as a server of remote Ubuntu 14.04

Recently the 13″ MBPr got upgrade to macOS Sierra 10.12. If I want to let it can act as remote X11 server of Ubuntu 14.04 (my main working VM in intranet), I have to install a X.Org X Window System that runs on macOS.

XQuartz is for this purpose , see https://www.xquartz.org/.

Then the file /etc/ssh/sshd_conf needs to be modified, and the ssh service needs up. After ssh to Ubuntu, there are some error/warning messages:
[code language=”bash” light=”true”]
Last login: Thu Oct 6 14:32:12 2016 from 10.0.0.1
manpath: can’t set the locale; make sure $LC_* and $LANG are correct
linkirin@trusty:~$ gvim
Fontconfig warning: ignoring UTF-8: not a valid region tag
[/code]

To fix these, add two more lines in the file:
[code language=”bash” light=”true”]
linkirin@trusty:~$ cat /etc/default/locale
LANG="en_US.UTF-8"

linkirin@trusty:~$ cat /etc/default/locale
LANG="en_US.UTF-8"
LANGUAGE="en_US.UTF-8"
LC_ALL="en_US.UTF-8"
[/code]
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