2 GPUs installed on system, but only 1 attached by nvidia-smi

dawn@ccnt-cv:~ lspci | grep VGA 04:00.0 VGA compatible controller: NVIDIA Corporation GP102 [GeForce GTX 1080 Ti] (rev a1) 09:00.0 VGA compatible controller: Matrox Electronics Systems Ltd. G200eR2 (rev 01) 83:00.0 VGA compatible controller: NVIDIA Corporation GP102 [GeForce GTX 1080 Ti] (rev a1) dawn@ccnt-cv:~ 0NT78X

v:~ dmesg | grep NVRM [ 17.441538] NVRM: loading NVIDIA UNIX x86_64 Kernel Module 415.27 Thu Dec 20 17:25:03 CST 2018 (using threaded interrupts) [ 30.993134] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 30.993201] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 64.573846] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 64.573875] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 68.472908] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 68.472939] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 70.691272] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 70.691301] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 79.038052] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 79.038081] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 117.844816] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 117.844846] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 149.787528] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 149.787558] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 153.008244] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 153.008276] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 365.486355] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 365.486384] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 1892.846906] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 1892.846934] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 1897.969947] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 1897.969980] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 2163.945909] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 2163.945939] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 2368.710101] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 2368.710132] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 2854.814346] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 2854.814377] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 2905.888762] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 2905.888793] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 3390.603718] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 3390.603750] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 3777.412796] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 3777.412829] NVRM: rm_init_adapter failed for device bearing minor number 1 [ 3842.887841] NVRM: RmInitAdapter failed! (0x31:0xffff:826) [ 3842.887885] NVRM: rm_init_adapter failed for device bearing minor number 1 dawn@ccnt-cv:~

dawn@ccnt-cv:~$ nvidia-smi
Sat Mar 23 14:01:22 2019
±----------------------------------------------------------------------------+
| NVIDIA-SMI 415.27 Driver Version: 415.27 CUDA Version: 10.0 |
|-------------------------------±---------------------±---------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
|===============================+======================+======================|
| 0 GeForce GTX 108… Off | 00000000:04:00.0 Off | N/A |
| 88% 71C P2 252W / 260W | 10391MiB / 11178MiB | 100% Default |
±------------------------------±---------------------±---------------------+

±----------------------------------------------------------------------------+
| Processes: GPU Memory |
| GPU PID Type Process name Usage |
|=============================================================================|
| 0 3910 C python 10381MiB |
±----------------------------------------------------------------------------+
dawn@ccnt-cv:~$

your driver install may be broken

one of the GPUs may be defective

one of the GPUs may not be installed correctly, e.g. not having all necessary power cables

there may be a system incompatibility issue

And there are probably other possibilities