System:  mysogo, 13.2, xen guest. 

When issuing an apache reload:

# systemctl reload apache2
Job for apache2.service failed. See "systemctl status apache2.service" and
"journalctl -xn" for details.

# systemctl status apache2
apache2.service - The Apache Webserver
   Loaded: loaded (/usr/lib/systemd/system/apache2.service; enabled)
   Active: active (running) (Result: exit-code) since Sun 2016-08-07 12:02:18
CEST; 3 weeks 1 days ago
  Process: 5711 ExecReload=/usr/sbin/start_apache2 -D SYSTEMD -DFOREGROUND -k
graceful (code=exited, status=226/NAMESPACE)
 Main PID: 854 (httpd2-prefork)
   Status: "Total requests: 0; Current requests/sec: 0; Current traffic:   0
B/sec"
   CGroup: /system.slice/apache2.service
           ������  854 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������ 1468 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������ 1472 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������ 1474 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������ 1487 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������ 3398 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������ 3400 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������10336 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������32256 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������32280 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start
           ������32478 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -DSSL -D
SYSTEMD -DFOREGROUND -k start

Aug 30 11:12:31 mysogo systemd[1]: Reloading The Apache Webserver.
Aug 30 11:12:31 mysogo systemd[5711]: Failed at step NAMESPACE spawning
/usr/sbin/start_apache2: Operation not permitted
Aug 30 11:12:31 mysogo systemd[1]: apache2.service: control process exited,
code=exited status=226
Aug 30 11:12:31 mysogo systemd[1]: Reload failed for The Apache Webserver.
Warning: Journal has been rotated since unit was started. Log output is
incomplete or unavailable.

A similar issue is mentioned here:

https://help.directadmin.com/item.php?id=614

but on my system, both /tmp and /var/tmp are directories, not symlinks.