Exercise 1 - Devices

1. Suppose an operating system is unable to boot after adding a second SATA disk to the system. Knowing that all parts are not defective, what could be the possible cause for this error?
   
   
   The boot device order should be configured in the BIOS setup utility, otherwise the BIOS may not able to run the bootloader.
   
   
2. Suppose you want to make sure the external video card connected to the PCI bus of your newly acquired desktop computer really is the one advertised by the manufacturer, but opening the computer case will void the warranty. What command could be used to list the details of the video card, as they were detected by the operating system?
   
   
   Command lspci will list detailed information about all devices currently connected to the PCI bus.
   
   
3. The following line is part of the output generated by command lspci:
   
   What command should you execute to identify the kernel module in use for this specific device?
   
   
   The command lspci -s 03:00.0 -v or lspci -s 03:00.0 -k
   
   
4. A system administrator wants to try different parameters for the bluetooth kernel module without rebooting the system. However, any attempt to unload the module with modprobe -r bluetooth results in the following error:
   
   What is the possible cause for this error?
   
   
   Module bluetooth is being used by a running process.
   
   
5. It is not uncommon to find legacy machines in production environments, like when some equipment uses an outdated connection to communicate with the controlling computer, making it necessary to pay special attention to some peculiarities of these older machines. Some x86 servers with older BIOS firmware, for example, will not boot if a keyboard is not detected. How can this particular issue be avoided?
   
   
   The BIOS configuration utility has an option to deactivate the locking of the computer when a keyboard is not found.
   
   
6. Operating systems built around the Linux kernel are also available for a wide variety of computer architectures other than x86, like in single board computers based on the ARM architecture. An attentive user will notice the absence of the lspci command on such machines, like the Raspberry Pi. What difference with x86 machines justifies that absence?
   
   
   Unlike most x86 machines, an ARM based computer like the Raspberry Pi lacks a PCI bus, so the command lspci is useless.
   
   
7. Many network routers have a USB port allowing for the connections of an external device, like a USB hard drive. Since most of these are using a Linux based operating system, how will an external USB hard drive be named in the /dev/ directory, assuming no other conventional block device is present in the router?
   
   
   Modern Linux kernels identify USB hard drives as SATA devices, so the corresponding file will be /dev/sda as no other conventional block device exists in the system.
   
   
8. In 2018, the hardware vulnerability known as Meltdown was discovered. It affects almost all processors of many architectures. Recent versions of the Linux kernel can inform if the current system is vulnerable. How can this information be obtained?
   
   
   The file /proc/cpuinfo has a line showing the known bugs for the corresponding CPU, like bugs: cpu_meltdown.