Troubleshooting & Common Issues

Common problems and their solutions.

Contents

• Quick fixes
• Docker issues
• Nextcloud problems
• Network issues
• Drive/mount issues
• Permission problems
• Package management
• Media server issues
• Display/GUI issues
• System issues
• General debugging tips
• Still stuck?

---

Quick fixes

"Permission denied"

# Add sudo
sudo [your command]

# Or change file permissions
chmod +x filename.sh

"Command not found"

# Install the missing package
sudo apt install [package-name]  # Debian/Ubuntu
sudo dnf install [package-name]  # Fedora
sudo pacman -S [package-name]    # Arch

"No space left on device"

# Check disk usage
df -h

# Find large files
du -h --max-depth=1 / | sort -h

# Clean package cache
sudo apt clean  # Debian/Ubuntu

---

Docker issues

Docker command requires sudo

# Add user to docker group
sudo usermod -aG docker $USER
# Log out and back in

Container won't start

# Check logs
docker logs [container-name]

# Check if ports are in use
sudo netstat -tlnp | grep [port]

"Cannot connect to Docker daemon"

# Start Docker service
sudo systemctl start docker
sudo systemctl enable docker

Related: Docker Setup

---

Nextcloud problems

"Internal server error"

1. Check PHP version compatibility
2. Review logs: /var/log/apache2/error.log
3. Fix permissions:

sudo chown -R www-data:www-data /var/www/nextcloud

Slow performance

• Enable Redis caching
• Increase PHP memory limit
• Use MariaDB instead of SQLite

"Untrusted domain" error

Edit config/config.php:

'trusted_domains' => 
  array (
    0 => 'your-domain.com',
    1 => '192.168.1.x',
  ),

Related: Docker Nextcloud · Nextcloud USB Drive

---

Network issues

Can't access service from other devices

1. Check firewall:

sudo ufw status
sudo ufw allow [port]

2. Check service is listening on all interfaces:

netstat -tlnp | grep [port]
# Should show 0.0.0.0:[port] not 127.0.0.1:[port]

DNS not resolving

# Test DNS
nslookup google.com

# Edit DNS servers
sudo nano /etc/resolv.conf
# Add: nameserver 1.1.1.1

---

Drive/mount issues

USB drive not mounting

# List all drives
lsblk

# Manual mount
sudo mkdir /mnt/usb
sudo mount /dev/sdX1 /mnt/usb

"Read-only file system"

# Remount as read-write
sudo mount -o remount,rw /

# Check filesystem
sudo fsck /dev/sdX1

Related: Mount Commands

---

Permission problems

Can't edit system files

# Use sudo with text editor
sudo nano /etc/file.conf

# Or change ownership (carefully!)
sudo chown $USER:$USER /path/to/file

Script won't execute

# Make executable
chmod +x script.sh

# Or run with interpreter
bash script.sh

---

Package management

Broken dependencies (Debian/Ubuntu)

sudo apt --fix-broken install
sudo dpkg --configure -a

"Unable to locate package"

# Update package lists
sudo apt update

# Search for correct name
apt search [partial-name]

Held packages

# List held packages
apt-mark showhold

# Unhold package
sudo apt-mark unhold [package]

---

Media server issues

Plex can't find media

• Check file permissions
• Verify correct library paths
• Ensure proper file naming convention

Transcoding problems

• Install ffmpeg
• Check CPU usage during playback
• Consider hardware acceleration

Related: Plex Media Server

---

Display/GUI issues

Black screen after login

1. Switch to TTY: Ctrl+Alt+F2
2. Login and check logs:

journalctl -xe

3. Reinstall display drivers if needed

Resolution problems

# List displays
xrandr

# Set resolution
xrandr --output [display] --mode 1920x1080

---

System issues

System won't boot

1. Boot to recovery mode
2. Check filesystem: fsck -f /
3. Review boot logs: journalctl -b

High CPU/memory usage

# Check processes
htop
top

# Kill problematic process
kill -9 [PID]

Service won't start

# Check status
systemctl status [service]

# View logs
journalctl -u [service]

# Restart service
sudo systemctl restart [service]

---

General debugging tips

1. Always check logs

• System: journalctl -xe
• Service: journalctl -u [service]
• Application: Usually in /var/log/

2. Google the error

• Include distro name
• Include software version
• Look for recent results

3. Ask for help properly

When asking for help, provide:

• Exact error message
• What you were trying to do
• Your system info: uname -a
• What you've already tried

---

Still stuck?

Community help

• The Linux Cast Discord
• Linux Questions Forum
• Reddit: r/linux4noobs, r/linuxquestions

Direct contact

• Contact - Reach out to me
• Include error details and what you've tried

Useful commands for troubleshooting

# System info
uname -a
lsb_release -a

# Hardware info
lspci
lsusb
lscpu

# Memory info
free -h
df -h

# Network info
ip a
ping -c 4 google.com

# Process info
ps aux
htop

# Log viewing
tail -f /var/log/syslog
journalctl -f