When i run the line you said this is what i get in return and it looks to be all good, this is the pre configured VM.

indi@ekos-vm:~$ ls -al /dev/ttyUSB*
crw-rw-rw- 1 root dialout 188, 0 Apr  5 19:03 /dev/ttyUSB0

When I do a quick test this is what i get, note it thinks the capture is being taken, but the shutter never went off.
INFO	88.259047 sec	: Session log file /tmp/indi_gphoto_ccd_2017-04-05T16:03:50.log
DEBUG	106.009442 sec	: Starting exposure (exptime: 60 secs, mirror lock: 0)
DEBUG	106.009467 sec	:   Mutex locked
DEBUG	106.009963 sec	: looking for bulb exposure..
DEBUG	106.009974 sec	: bulb exposure found! id:52
DEBUG	106.009980 sec	: Using bulb mode. idx: 52
DEBUG	106.036425 sec	: Exposure started
INFO	106.036473 sec	: Starting 60 sec exposure
DEBUG	106.036540 sec	: Time left: 59974
DEBUG	107.036624 sec	: Capture in progress. Time left 59
DEBUG	108.037240 sec	: Capture in progress. Time left 58
DEBUG	109.037489 sec	: Capture in progress. Time left 56
DEBUG	110.038674 sec	: Capture in progress. Time left 55
DEBUG	111.037372 sec	: Time left: 54974
DEBUG	111.039024 sec	: Capture in progress. Time left 54
DEBUG	112.039169 sec	: Capture in progress. Time left 53
DEBUG	113.039407 sec	: Capture in progress. Time left 52
DEBUG	114.039616 sec	: Capture in progress. Time left 51
DEBUG	115.040532 sec	: Capture in progress. Time left 50
DEBUG	116.037459 sec	: Time left: 49973
DEBUG	116.040599 sec	: Capture in progress. Time left 49
DEBUG	117.041586 sec	: Capture in progress. Time left 48
DEBUG	118.041973 sec	: Capture in progress. Time left 47
DEBUG	119.042517 sec	: Capture in progress. Time left 46
DEBUG	120.043198 sec	: Capture in progress. Time left 45
DEBUG	121.037822 sec	: Time left: 44973
DEBUG	121.046658 sec	: Capture in progress. Time left 44
DEBUG	122.046839 sec	: Capture in progress. Time left 43
DEBUG	123.047039 sec	: Capture in progress. Time left 42
DEBUG	124.047246 sec	: Capture in progress. Time left 41
DEBUG	125.047492 sec	: Capture in progress. Time left 40
DEBUG	126.038233 sec	: Time left: 39973
DEBUG	126.047866 sec	: Capture in progress. Time left 39
DEBUG	127.047972 sec	: Capture in progress. Time left 38
DEBUG	128.048472 sec	: Capture in progress. Time left 37
DEBUG	129.049436 sec	: Capture in progress. Time left 36
DEBUG	130.049731 sec	: Capture in progress. Time left 35
DEBUG	131.038951 sec	: Time left: 34972
DEBUG	131.061815 sec	: Capture in progress. Time left 34
DEBUG	132.062541 sec	: Capture in progress. Time left 33
DEBUG	133.062716 sec	: Capture in progress. Time left 32
DEBUG	134.063649 sec	: Capture in progress. Time left 31
DEBUG	135.063855 sec	: Capture in progress. Time left 30
DEBUG	136.039087 sec	: Time left: 29972
DEBUG	136.064883 sec	: Capture in progress. Time left 29
DEBUG	137.064966 sec	: Capture in progress. Time left 28
DEBUG	138.065921 sec	: Capture in progress. Time left 27
DEBUG	139.066314 sec	: Capture in progress. Time left 26
DEBUG	140.066424 sec	: Capture in progress. Time left 25
DEBUG	141.039339 sec	: Time left: 24972
DEBUG	141.066557 sec	: Capture in progress. Time left 24
DEBUG	142.066650 sec	: Capture in progress. Time left 23
DEBUG	143.067086 sec	: Capture in progress. Time left 22
DEBUG	144.067269 sec	: Capture in progress. Time left 21
DEBUG	145.067367 sec	: Capture in progress. Time left 20
DEBUG	146.039435 sec	: Time left: 19971
DEBUG	146.068119 sec	: Capture in progress. Time left 19
DEBUG	147.068749 sec	: Capture in progress. Time left 18
DEBUG	148.069082 sec	: Capture in progress. Time left 17
DEBUG	149.069500 sec	: Capture in progress. Time left 16
DEBUG	150.069816 sec	: Capture in progress. Time left 15
DEBUG	151.040298 sec	: Time left: 14971
DEBUG	151.070617 sec	: Capture in progress. Time left 14
DEBUG	152.070728 sec	: Capture in progress. Time left 13
DEBUG	153.071221 sec	: Capture in progress. Time left 12
DEBUG	154.071865 sec	: Capture in progress. Time left 11
DEBUG	155.072302 sec	: Capture in progress. Time left 10
DEBUG	156.040536 sec	: Time left: 9970
DEBUG	156.072861 sec	: Capture in progress. Time left 9
DEBUG	157.073039 sec	: Capture in progress. Time left 8
DEBUG	158.073533 sec	: Capture in progress. Time left 7
DEBUG	159.073721 sec	: Capture in progress. Time left 6
DEBUG	160.073819 sec	: Capture in progress. Time left 5
DEBUG	161.040723 sec	: Time left: 4970
DEBUG	161.074533 sec	: Capture in progress. Time left 4
DEBUG	162.074697 sec	: Capture in progress. Time left 3
DEBUG	163.075911 sec	: Capture in progress. Time left 2
DEBUG	164.076027 sec	: Capture in progress. Time left 1
DEBUG	165.076274 sec	: Reading exposure
DEBUG	166.011030 sec	: Time left: 0
DEBUG	166.011083 sec	: Closing shutter
DEBUG	166.034514 sec	: Exposure complete
DEBUG	166.706890 sec	: Got unexpected message: 1
DEBUG	167.380639 sec	: Got unexpected message: 1
DEBUG	168.051348 sec	: Got unexpected message: 1
DEBUG	168.719837 sec	: Got unexpected message: 1
DEBUG	169.392856 sec	: Got unexpected message: 1
DEBUG	170.061772 sec	: Got unexpected message: 1
DEBUG	170.732980 sec	: Got unexpected message: 1
DEBUG	171.407513 sec	: Got unexpected message: 1
DEBUG	172.076294 sec	: Got unexpected message: 1
DEBUG	172.742655 sec	: Got unexpected message: 1
DEBUG	173.410153 sec	: Got unexpected message: 1
DEBUG	174.077954 sec	: Got unexpected message: 1
DEBUG	174.747901 sec	: Got unexpected message: 1
DEBUG	175.422338 sec	: Got unexpected message: 1
DEBUG	176.091737 sec	: Got unexpected message: 1
DEBUG	176.763178 sec	: Got unexpected message: 1
DEBUG	177.435521 sec	: Got unexpected message: 1
DEBUG	178.109289 sec	: Got unexpected message: 1
DEBUG	178.776288 sec	: Got unexpected message: 1
DEBUG	179.440423 sec	: Got unexpected message: 1
DEBUG	180.111328 sec	: Got unexpected message: 1
DEBUG	180.781275 sec	: Got unexpected message: 1
DEBUG	181.452019 sec	: Got unexpected message: 1
DEBUG	182.119860 sec	: Got unexpected message: 1
DEBUG	182.786674 sec	: Got unexpected message: 1
DEBUG	183.457614 sec	: Got unexpected message: 1
DEBUG	184.130769 sec	: Got unexpected message: 1
DEBUG	184.803085 sec	: Got unexpected message: 1
DEBUG	185.471962 sec	: Got unexpected message: 1
DEBUG	186.140994 sec	: Got unexpected message: 1
DEBUG	186.815252 sec	: Got unexpected message: 1
DEBUG	187.483591 sec	: Got unexpected message: 1
DEBUG	188.153465 sec	: Got unexpected message: 1
DEBUG	188.826256 sec	: Got unexpected message: 1
DEBUG	189.497154 sec	: Got unexpected message: 1
DEBUG	190.168272 sec	: Got unexpected message: 1
DEBUG	190.839675 sec	: Got unexpected message: 1
DEBUG	191.514931 sec	: Got unexpected message: 1
DEBUG	192.191017 sec	: Got unexpected message: 1
DEBUG	192.855407 sec	: Got unexpected message: 1
DEBUG	193.528816 sec	: Got unexpected message: 1
DEBUG	194.196917 sec	: Got unexpected message: 1
DEBUG	194.871927 sec	: Got unexpected message: 1
DEBUG	195.542655 sec	: Got unexpected message: 1
DEBUG	196.217155 sec	: Got unexpected message: 1
DEBUG	196.888190 sec	: Got unexpected message: 1
DEBUG	197.555986 sec	: Got unexpected message: 1
DEBUG	198.229960 sec	: Got unexpected message: 1
DEBUG	198.898562 sec	: Got unexpected message: 1
DEBUG	199.570129 sec	: Got unexpected message: 1
DEBUG	200.241983 sec	: Got unexpected message: 1
DEBUG	200.915109 sec	: Got unexpected message: 1
DEBUG	201.584646 sec	: Got unexpected message: 1
DEBUG	202.252128 sec	: Got unexpected message: 1
DEBUG	202.924925 sec	: Got unexpected message: 1
DEBUG	203.594816 sec	: Got unexpected message: 1
DEBUG	204.264908 sec	: Got unexpected message: 1
DEBUG	204.935060 sec	: Got unexpected message: 1
DEBUG	205.601333 sec	: Got unexpected message: 1
DEBUG	206.273497 sec	: Got unexpected message: 1
DEBUG	206.942964 sec	: Got unexpected message: 1
DEBUG	207.613443 sec	: Got unexpected message: 1
DEBUG	208.285592 sec	: Got unexpected message: 1
DEBUG	208.954773 sec	: Got unexpected message: 1
DEBUG	209.624549 sec	: Got unexpected message: 1
DEBUG	210.293393 sec	: Got unexpected message: 1
DEBUG	210.960416 sec	: Got unexpected message: 1
DEBUG	211.633241 sec	: Got unexpected message: 1
DEBUG	212.300787 sec	: Got unexpected message: 1
DEBUG	212.968319 sec	: Got unexpected message: 1
DEBUG	213.643397 sec	: Got unexpected message: 1
DEBUG	214.312389 sec	: Got unexpected message: 1
DEBUG	214.983806 sec	: Got unexpected message: 1
DEBUG	215.657248 sec	: Got unexpected message: 1
DEBUG	216.327074 sec	: Got unexpected message: 1
DEBUG	216.999564 sec	: Got unexpected message: 1
DEBUG	217.667864 sec	: Got unexpected message: 1
DEBUG	218.338367 sec	: Got unexpected message: 1
DEBUG	219.008008 sec	: Got unexpected message: 1
DEBUG	219.673973 sec	: Got unexpected message: 1
DEBUG	220.349035 sec	: Got unexpected message: 1
DEBUG	221.017029 sec	: Got unexpected message: 1
DEBUG	221.687586 sec	: Got unexpected message: 1
DEBUG	222.356925 sec	: Got unexpected message: 1
DEBUG	223.028942 sec	: Got unexpected message: 1
DEBUG	223.702957 sec	: Got unexpected message: 1
DEBUG	224.373218 sec	: Got unexpected message: 1
DEBUG	225.043269 sec	: Got unexpected message: 1
DEBUG	225.711265 sec	: Got unexpected message: 1
DEBUG	226.378435 sec	: Got unexpected message: 1
DEBUG	227.048839 sec	: Got unexpected message: 1
DEBUG	227.715883 sec	: Got unexpected message: 1
DEBUG	228.386114 sec	: Got unexpected message: 1
DEBUG	229.058494 sec	: Got unexpected message: 1

And hardware wise its a simple FTDI Cable with the RTS line connected to a PNP transistor which in turn grounds the shutter and focus pins together (Nikon needs both grounded to take an exposure). I dont know if its worth noting but it works just fine on windows but i tried DSLR shutter on a mac and its not

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