Hardware and System Performance
Disks, CPU, RAM, etc

Check devices and connections
List disks 
 lsblk 
 List PCI controller connections: 
 lspci 
 List CPU details 
 lscpu 
 List USB bus devices 
 lsusb

RAM
View current RAM configuration 
 lsmem 
 View current RAM usage (human readable) 
 free -h 
 Older systems might not like -h, you can also run the command without it.