www.makemkv.com

mshannon@octopod:~/BD$ makemkvcon backup disc:/media/TRUEBLOOD_S1_D1 ~/BD/TB-S1-D1/.
MakeMKV v1.6.3 linux(x64-release) started
Debug logging enabled, log will be saved as /home/mshannon/MakeMKV_log.txt
Error 'Scsi error - ILLEGAL REQUEST:INVALID COMMAND OPERATION CODE' occurred while issuing SCSI command 46020..00140 to device 'SG:dev_11:2'
DEBUG: Code 0 at RN=CQyKW2s;o^qgr:121267615
Error 'Scsi error - ILLEGAL REQUEST:INVALID COMMAND OPERATION CODE' occurred while issuing SCSI command 46020..00140 to device 'SG:dev_11:2'
DEBUG: Code 0 at RN=CQyKW2s;o^qgr:121267615
Error 'Scsi error - ILLEGAL REQUEST:INVALID COMMAND OPERATION CODE' occurred while issuing SCSI command 46020..00140 to device 'SG:dev_11:2'
DEBUG: Code 0 at RN=CQyKW2s;o^qgr:121267615
Backing up disc into folder "/home/mshannon/BD/TB-S1-D1/."
DEBUG: Code 0 at T;S3nv8)GBL$vD:29399680
DEBUG: Code 0 at MX2:RIFM!M(>\PGA8wr2:29400347
DEBUG: Code 0 at MX2:RIFM!M(>\PGA8wr2:29401014
DEBUG: Code 0 at MX2:RIFM!M(>\PGA8wr2:29403682
Backup failed
Backup failed.
mshannon@octopod:~/BD$

You need to specify disc id or disc device name on command line. Try "disc:0" .