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Linux diagnostics

Linux diagnostics

System Information¶

Display general information about the system:
```
uname -a
```
Show system architecture and kernel version:
```
lscpu
```
Check OS version and distribution:
```
cat /etc/os-release
```

Disk and Filesystem Diagnostics¶

Check disk usage by filesystem:
```
df -h
```
Check filesystem errors:
```
fsck /dev/sdX
```
Display file and directory disk space usage:
```
du -h --max-depth=1
```
View disk partitions:
```
lsblk
```
Test disk I/O speed:
```
hdparm -tT /dev/sdX
```

Memory Diagnostics¶

Check free and used memory:
```
free -h
```
Real-time memory usage summary:
```
watch -n 1 free -h
```
Analyze memory usage by process:
```
smem
```
Install smem using sudo apt install smem or your package manager.

CPU Performance¶

Monitor real-time processes and CPU usage:
```
top
```
Show live CPU usage per core:
```
htop
```
Install htop using sudo apt install htop or your package manager.
- Display CPU frequencies:
```
cpufreq-info
```
Install cpufrequtils if not pre-installed.

Network Diagnostics¶

Display active network interfaces:
```
ip a
```
Test connectivity (ping a server):
```
ping google.com
```
Display open ports and listening services:
```
netstat -tuln
```
Use ss -tuln on modern systems (preferred).
- Check network speed:
```
speedtest-cli
```
Install speedtest-cli using sudo apt install speedtest-cli.

Logs and Errors¶

View system logs:
```
journalctl -xe
```
Display kernel messages:
```
dmesg | tail -n 50
```
Check authentication logs:
```
cat /var/log/auth.log
```

Process Diagnostics¶

Display active processes (real-time):
```
ps aux
```
Kill a hung process (replace <pid> with the process ID):
```
kill -9 <pid>
```
Find and debug a specific process:
```
pgrep -a <process_name>
```

Hardware Information¶

Check hardware (detailed overview):
```
lshw
```

Check battery status (for laptops):

upower -i /org/freedesktop/UPower/devices/battery_BAT0

Show PCI devices:
```
lspci
```
List USB devices:
```
lsusb
```

System Load and Uptime¶

Check system uptime:
```
uptime
```
Analyze load averages:
```
w
```
Read detailed stats of CPU load:
```
vmstat 1
```

Package Management¶

Check installed packages (Debian-based):
```
dpkg --get-selections
```
Search for a package:
```
apt search <package_name>
```
Update and upgrade packages:
```
sudo apt update && sudo apt upgrade
```

Debugging Kernel Issues¶

Debug kernel modules:
```
lsmod
dmesg | grep <module_name>
```
Remove a kernel module:
```
sudo modprobe -r <module_name>
```

Storage Device Health¶

SMART disk health check:
```
sudo smartctl -a /dev/sdX
```
Install smartmontools for smartctl if not installed.
Test for bad blocks:
```
sudo badblocks -v /dev/sdX
```

Backup and Recovery¶

Create disk or partition backup:

dd if=/dev/sdX of=backup.img bs=64K conv=noerror,sync

Compress backup:
```
gzip backup.img
```

Security Diagnostics¶

Check open ports for services:
```
sudo nmap -sT localhost
```
Check file permissions and ownership:
```
ls -l
```
Detect SUID binaries:
```
find / -perm -4000
```

Useful Extras¶

Show the last system reboot:
```
last reboot
```
Monitor all system services:
```
systemctl list-units --type=service
```
Check a service's status:
```
systemctl status <service_name>
```