User cannot start X (device already taken)

[Haines Brown <haines@histomat.net>]

Running Devuan Chimaera

Without doing anything unusual, suddenly can no longer start X, while 
root can do it. This is what is returned to terminal:

...
(II) [libseat/backend/seatd.c: 64] Could not connect to socket
     /run/seat.sock: no such file or directory
(II) [libseat/libseat.c: 76] Backend 'seatd' failed to open seat,
     skipping
(II) [libseat/libseat.c: 73] Seat opened with backend 'logind'
(DB) [libseat/backend/logind.c: 161] DRM device opened, current
     total: 1
xf86EnableIO: failed to enable I/O Ports 0000-03ff (Operation not
permitted
(EE) [libseat/backend/logind.c: 137] Could not take device: Device
      aleady taken
(II) Server terminated.


This is extract from Xorfg.0.log after user fails to start X

...
[ 49400.912] (II) UnloadModule: "libinput"
[ 49400.912] (II) seatd_libseat try close /dev/input/event18 (36:36)
[ 49400.912] (EE) [libseat/backend/logind.c:184] Could not stat fd 36
[ 49400.912] (EE) seatd_libseat close failed -9
[ 49400.912] (II) UnloadModule: "libinput"
[ 49400.912] (II) seatd_libseat try close /dev/input/event16 (35:35)
[ 49400.928] (II) UnloadModule: "libinput"
[ 49400.928] (II) seatd_libseat try close /dev/input/event20 (34:34)
[ 49400.928] (EE) [libseat/backend/logind.c:184] Could not stat fd 34
[ 49400.928] (EE) seatd_libseat close failed -9
...

Help much appreciated

-- 

     Haines Brown