1. System Won’t Boot

Symptoms: Blank screen, stuck at boot logo, or GRUB errors.

Common Causes:

• Corrupted bootloader

• Improper shutdown or power loss

• Disk errors

Solution:

• Reinstall GRUB:

sudo grub-install /dev/sda
sudo update-grub

• Check disk for errors:

sudo fsck /dev/sda1

• Boot from a live USB to repair the system

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2. Disk Full / No Space Left

Symptoms: Cannot save files, system slows down.

Diagnosis:

df -h
du -sh ~/*

Solution:

• Delete large unnecessary files:

rm -rf ~/Downloads/old_files/*

• Clean package cache:

sudo apt-get clean      # Ubuntu/Debian
sudo yum clean all      # CentOS/RHEL

• Find largest files:

find / -type f -size +100M -exec ls -lh {} \;

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3. High CPU or Memory Usage

Symptoms: System freezes, fan runs constantly, slow performance.

Diagnosis:

top
htop        # if installed

Common Causes:

• Processes consuming excessive resources

• Memory leaks in applications

Solution:

• Kill problematic process:

kill -9 <PID>

• Restart services if needed

• Upgrade or reinstall software causing leaks

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4. Network Problems

Symptoms: Cannot access websites, ping fails, download issues.

Diagnosis:

ping 8.8.8.8
ifconfig      # or ip addr
traceroute google.com

Common Causes:

• Misconfigured network settings

• DNS or firewall issues

Solution:

• Restart network:

sudo systemctl restart NetworkManager

• Check firewall:

sudo ufw status
sudo iptables -L

• Reset DNS settings in /etc/resolv.conf

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5. Package Management Errors

Symptoms: Cannot install or update software.

Common Causes:

• Broken packages

• Conflicting dependencies

• Outdated repository information

Solution (Ubuntu/Debian):

sudo apt update
sudo apt --fix-broken install
sudo dpkg --configure -a
sudo apt-get clean
sudo apt-get upgrade

Solution (CentOS/RHEL):

sudo yum clean all
sudo yum update

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6. Permissions Issues

Symptoms: Cannot access files, “Permission denied” errors.

Common Causes:

• Incorrect file ownership

• Missing sudo/root access

Solution:

• Change ownership:

sudo chown username:group filename

• Modify permissions:

sudo chmod 755 filename

• Use sudo for administrative tasks

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7. Slow Boot / System Lag

Symptoms: Long startup, delayed responses.

Common Causes:

• Too many startup services

• Heavy desktop environment

Solution:

• Disable unnecessary services:

sudo systemctl disable servicename

• Use lightweight desktop environments like XFCE or LXDE

• Check logs for boot delays:

systemd-analyze blame

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8. Kernel Panic or System Crashes

Symptoms: Black screen with error codes, kernel messages.

Common Causes:

• Hardware incompatibility

• Corrupted kernel modules

Solution:

• Boot using an older kernel from GRUB

• Update or reinstall kernel:

sudo apt-get install --reinstall linux-image-$(uname -r)

• Check hardware and drivers

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9. Disk Mounting Issues

Symptoms: External drives or partitions not accessible.

Common Causes:

• Filesystem corruption

• Wrong mount points

Solution:

• Mount manually:

sudo mount /dev/sdb1 /mnt

• Check filesystem:

sudo fsck /dev/sdb1

• Update /etc/fstab for permanent mounts

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10. Log Files Overgrowth

Symptoms: Disk usage spikes, system slowdowns.

Solution:

• Delete old logs:

sudo find /var/log -type f -name "*.log" -mtime +30 -exec rm -f {} \;

• Rotate logs using logrotate

• Monitor log sizes regularly