LWM-Linux/14 - Linux Troubleshooting and Recovery/Troubleshooting Hardware and Device Drivers.md

# Troubleshooting Hardware and Device Drivers

## 1. Identifying Hardware and Drivers

### a) List all hardware:
```
lshw
```
This command provides detailed information about your system's hardware configuration.

### b) List PCI devices:
```
lspci
```
Shows all PCI devices connected to your system.

### c) List USB devices:
```
lsusb
```
Displays all USB devices connected to your system.

### d) Check loaded kernel modules:
```
lsmod
```
Lists all currently loaded kernel modules (drivers).

## 2. Checking System Logs

### a) View kernel messages:
```
dmesg
```
Displays kernel-related messages, including hardware detection and driver loading.

### b) Check system logs:
```
journalctl
```
For systems using systemd, this command shows system logs.

## 3. Managing Drivers

### a) Load a module:
```
sudo modprobe module_name
```

### b) Unload a module:
```
sudo modprobe -r module_name
```

### c) Blacklist a module:
Add the following line to /etc/modprobe.d/blacklist.conf:
```
blacklist module_name
```

## 4. Troubleshooting Specific Hardware Types

### a) Network interfaces:
- Check network interface status:
  ```
  ip link show
  ```
- Bring an interface up or down:
  ```
  sudo ip link set interface_name up/down
  ```

### b) Graphics:
- Check graphics card information:
  ```
  lspci | grep VGA
  ```
- For NVIDIA GPUs, use:
  ```
  nvidia-smi
  ```

### c) Audio:
- List audio devices:
  ```
  aplay -l
  ```
- Check ALSA mixer settings:
  ```
  alsamixer
  ```

## 5. Firmware Issues

### a) Check for missing firmware:
```
dmesg | grep firmware
```

### b) Install firmware packages:
```
sudo apt install linux-firmware
```
(For Debian/Ubuntu-based systems)

## 6. Kernel Parameters

Modify kernel parameters by editing /etc/default/grub and updating GRUB_CMDLINE_LINUX_DEFAULT. After changes, run:
```
sudo update-grub
```

## 7. Driver Compilation

### If you need to compile a driver:
- a) Install build essentials:
```
sudo apt install build-essential linux-headers-$(uname -r)
```

- b) Download driver source, then typically:
```
make
sudo make install
```

## 8. Debugging Tools

- a) strace: Trace system calls and signals
```
strace command
```

- b) ltrace: Library call tracer
```
ltrace command
```

## 9. Hardware Information Tools

- a) inxi: Comprehensive hardware information
```
inxi -Fxz
```

- b) hwinfo: Another detailed hardware information tool
```
hwinfo --short
```

## 10. Kernel Configuration

Check current kernel configuration:
```
zcat /proc/config.gz
```
(If available)

## 11. Udev Rules

Manage device events and permissions by creating or modifying rules in /etc/udev/rules.d/.

## 12. Benchmarking and Stress Testing

- a) CPU stress test:
```
stress --cpu 8 --timeout 20s
```

- b) Disk benchmark:
```
sudo hdparm -tT /dev/sda
```

## 13. Power Management

a) Check CPU frequency scaling:
```
cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
```

b) Set performance mode:
```
echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
```

## 14. Troubleshooting Steps

1. Identify the problem hardware or driver
2. Check system logs for errors
3. Ensure correct drivers are installed and loaded
4. Try different kernel parameters
5. Update or downgrade drivers if necessary
6. Check for conflicts with other hardware or software
7. Test hardware in a live Linux environment to isolate OS issues

Remember to backup important data before making significant system changes. If you're unsure about any step, research further or seek help from the Linux community forums specific to your distribution.