systemd can't start daemon if its initscript is symliked onto a partition other than root.

Issue

• systemd can't start daemon if its initscript is a symliked file to a partition other than root.

  [root@server ~]# df / /mnt/test
  Filesystem  1K-blocks   Used Available Use% Mounted on
  /dev/sda2     6981632 990768   5990864  15% /
  /dev/sdb1     1044140  32932   1011208   4% /mnt/test
  [root@server ~]# ls -l /etc/rc.d/init.d/test_daemon
  lrwxrwxrwx. 1 root root 24 Oct 20 15:25 /etc/rc.d/init.d/test_daemon -> /mnt/test/test_daemon.sh
  [root@server ~]# reboot
  ...
  [root@server ~]# systemctl status test_daemon
  test_daemon.service - SYSV: Test Script
     Loaded: loaded (/etc/rc.d/init.d/test_daemon)
     Active: inactive (dead)
  

• If the real file of the initscript is placed in /etc/rc.d/init.d, the daemon is activated.

  [root@server ~]# ls -l /etc/rc.d/init.d/test_daemon*
  lrwxrwxrwx. 1 root root  14 Oct 20 15:56 /etc/rc.d/init.d/test_daemon -> test_daemon.sh
  -rwxr-xr-x. 1 root root 728 Oct 20 14:24 /etc/rc.d/init.d/test_daemon.sh
  [root@server ~]# reboot
  ...
  [root@server ~]# systemctl status test_daemon
  test_daemon.service - SYSV: Test Script
     Loaded: loaded (/etc/rc.d/init.d/test_daemon)
     Active: active (running) since Tue 2015-10-20 15:57:12 JST; 6s ago
    Process: 1076 ExecStart=/etc/rc.d/init.d/test_daemon start (code=exited, status=0/SUCCESS)
     CGroup: /system.slice/test_daemon.service
             └─1114 /usr/local/sbin/test_daemon