Part 10: First Boot and Post-Installation

Overview

Boot your LFS system for the first time, verify functionality, and perform post-installation tasks.

First Boot Procedure

1. Power On / Reboot

After following Part 9 and unmounting all filesystems:

# From host system
shutdown -r now

Or in a virtual machine, simply reboot.

2. GRUB Boot Menu

You should see:

GNU GRUB version 2.12

GNU/Linux, Linux 6.16.1-lfs-12.4
GNU/Linux, Linux 6.16.1-lfs-12.4 (recovery mode)

Use ↑ and ↓ to select which entry is highlighted.
Press enter to boot the selected OS, 'e' to edit the
commands before booting or 'c' for a command-line.

Press Enter to boot the default entry.

3. Boot Messages

You'll see kernel boot messages scrolling. Watch for:

[    0.000000] Linux version 6.16.1-lfs-12.4
[    0.000000] Command line: root=/dev/sda2 ro
...
[    2.345678] EXT4-fs (sda2): mounted filesystem with ordered data mode
...
[  OK  ] Started Create Volatile Files and Directories
[  OK  ] Started Network Time Synchronization
[  OK  ] Reached target Multi-User System

4. Login Prompt

After boot completes, you'll see:

Linux From Scratch 12.4 lfs tty1

lfs login:

Login as root with the password you set in Part 8.

login: root
Password: [your-password]

Initial System Verification

1. Verify System is Running

# Check kernel version
uname -a
# Should show: Linux lfs 6.16.1-lfs-12.4 ...

# Check distribution
cat /etc/lsb-release
cat /etc/os-release

# Check hostname
hostname
hostnamectl  # (if using systemd)

# Check uptime
uptime

2. Verify Filesystems

# Check mounted filesystems
df -h

# Expected output similar to:
# Filesystem      Size  Used Avail Use% Mounted on
# /dev/sda2        28G  4.2G   22G  16% /
# devtmpfs        485M     0  485M   0% /dev
# tmpfs           493M     0  493M   0% /dev/shm

# Verify fstab
cat /etc/fstab

# Check filesystem integrity
mount | grep "^/dev"

3. Test Network Connectivity

# Check network interfaces
ip addr show
# or
ifconfig -a

# Check if interface is up
ip link show eth0

# Bring up interface if down
ip link set eth0 up

# Test DHCP (if configured)
dhclient eth0  # or
dhcpcd eth0

# Test connectivity
ping -c 4 google.com

# If ping fails, check:
cat /etc/resolv.conf
cat /etc/sysconfig/ifconfig.eth0

4. Test Package Management

# Check GCC
gcc --version

# Check Bash
bash --version

# Check Python
python3 --version

# Test compilation
echo 'int main() { return 0; }' > test.c
gcc test.c -o test
./test
echo $?  # Should output: 0
rm test test.c

5. Verify System Services

For SysVinit:

# Check running init
ps -p 1

# Check runlevel
runlevel
# Should show: N 3 (or N 5)

For Systemd:

# Check systemd status
systemctl status

# List failed services
systemctl --failed

# List enabled services
systemctl list-unit-files --state=enabled

Post-Installation Configuration

1. Create Regular User Account

# Add a regular user (replace 'john' with your username)
useradd -m -G users,wheel,audio,video -s /bin/bash john

# Set user password
passwd john

# Test sudo access (if sudo installed)
su - john
sudo echo "test"
exit

2. Configure Time and Date

# Check current time
date

# Set timezone (if not already set)
ln -sfv /usr/share/zoneinfo/America/New_York /etc/localtime

# For systemd, use timedatectl
timedatectl set-timezone America/New_York
timedatectl set-ntp true

# Verify
timedatectl status

3. Update System Clock from Internet

For SysVinit:

# Install and configure NTP (if available)
# Or manually sync
ntpdate pool.ntp.org

For Systemd:

# Enable time sync
systemctl enable systemd-timesyncd
systemctl start systemd-timesyncd

# Check status
timedatectl status

4. Configure SSH (if needed)

If you built OpenSSH:

# Generate host keys
ssh-keygen -A

# Start SSH daemon
/usr/sbin/sshd

# Or with systemd
systemctl enable sshd
systemctl start sshd

# Check status
systemctl status sshd

5. Set up Firewall (Optional)

If you built iptables:

# Basic firewall rules
cat > /etc/iptables.rules << "EOF"
*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -p tcp --dport 22 -j ACCEPT
COMMIT
EOF

# Apply rules
iptables-restore < /etc/iptables.rules

# Save for boot
# Add to /etc/rc.d/init.d/iptables or systemd service

System Testing

1. Reboot Test

# Reboot the system
reboot

# After reboot, verify:
# - System boots successfully
# - Network comes up automatically
# - Services start correctly
# - Time is correct

2. Shutdown Test

# Test clean shutdown
shutdown -h now

# System should:
# - Stop all services gracefully
# - Unmount filesystems properly
# - Power off cleanly

3. Multi-User Test

# Login as regular user
# Verify user environment works
whoami
pwd
ls -la ~

4. Stress Test (Optional)

# CPU test
dd if=/dev/zero of=/dev/null &
# Watch with top, then kill when done
killall dd

# Disk test
dd if=/dev/zero of=/tmp/testfile bs=1M count=1024
rm /tmp/testfile

# Memory test
free -h

Troubleshooting Common Issues

Issue: No Network Connectivity

Solutions:

# Check interface name
ip addr show

# Bring up interface
ip link set eth0 up

# Get DHCP address
dhclient eth0

# Check routes
ip route show

# Add default route manually
ip route add default via 192.168.1.1

# Test DNS
ping 8.8.8.8  # IP works but domain doesn't?
echo "nameserver 8.8.8.8" >> /etc/resolv.conf
ping google.com

Issue: Cannot Login as Root

Solutions:

Reboot into single-user mode:
- At GRUB menu, press 'e'
- Add single to kernel line
- Boot with Ctrl+X
- Reset password: passwd root
Or add init=/bin/bash to kernel line:
- Mount root: mount -o remount,rw /
- Reset password: passwd root
- Reboot: exec /sbin/init

Issue: Services Won't Start

For SysVinit:

# Check service scripts
ls -l /etc/rc.d/init.d/

# Start manually
/etc/rc.d/init.d/network start

# Check logs
dmesg | tail
tail /var/log/messages

For Systemd:

# Check failed services
systemctl --failed

# Check specific service
systemctl status network.service

# View logs
journalctl -xe
journalctl -u network.service

Issue: Kernel Panic on Boot

Solutions:

Boot with recovery kernel (if you made one)
Check GRUB configuration:
- Ensure root= points to correct partition
- Verify partition exists: ls (hd0,2)/ in GRUB
Rebuild initramfs if using one
Check kernel has required drivers compiled in

Beyond LFS: Next Steps

1. Install Additional Software (BLFS)

Beyond Linux From Scratch (BLFS) provides instructions for:

X Window System (graphical interface)
Desktop environments (GNOME, KDE, XFCE)
Web browsers (Firefox, Chromium)
Office software (LibreOffice)
Media players
Development tools

BLFS Website: https://www.linuxfromscratch.org/blfs/

2. Create Automated Package Management

Consider implementing:

Package tracking system
Build scripts for common software
Dependency management
Update mechanism

3. System Hardening

Configure SELinux or AppArmor
Set up firewall rules
Enable audit logging
Configure automatic security updates

4. Backup Strategy

# Create system backup
tar -czpf /backup/lfs-system-$(date +%Y%m%d).tar.gz \
    --exclude=/proc \
    --exclude=/sys \
    --exclude=/dev \
    --exclude=/tmp \
    --exclude=/backup \
    /

# Create kernel config backup
cp /boot/config-6.16.1 /backup/

# Backup important configs
tar -czf /backup/etc-backup-$(date +%Y%m%d).tar.gz /etc

5. Document Your System

Create documentation for:

Installed packages list
Custom configurations
Kernel configuration choices
Network setup
User accounts and permissions

# Generate package list
cat > /root/package-list.txt << "EOF"
LFS 12.4 Installed Packages:
- Linux Kernel 6.16.1
- Glibc 2.42
- GCC 15.2.0
- Binutils 2.45
...
EOF

Performance Tuning

1. Optimize Boot Time

# Analyze boot time (systemd)
systemd-analyze
systemd-analyze blame
systemd-analyze critical-chain

# Disable unnecessary services
systemctl disable <service-name>

2. Filesystem Optimization

# Tune ext4 filesystem
tune2fs -l /dev/sda2

# Enable journaling optimizations
tune2fs -O dir_index /dev/sda2

3. Kernel Optimization

Rebuild kernel with optimizations:

Enable only needed drivers
Compile for specific CPU (CONFIG_MCORE2, etc.)
Enable compiler optimizations

Congratulations!

You have successfully built Linux From Scratch 12.4!

What you've accomplished:

✅ Built a complete Linux system from source
✅ Learned how Linux systems work internally
✅ Compiled ~102 packages totaling 900+ MB
✅ Configured system services and network
✅ Installed kernel and bootloader
✅ Created a working, bootable operating system

Final Checklist

System boots successfully
Root login works
Network is configured and working
Time and timezone are correct
Regular user account created
System services are running
Filesystem is clean and organized
Backup created
Documentation written

Resources

LFS Official Site: https://www.linuxfromscratch.org/
LFS Book: https://www.linuxfromscratch.org/lfs/view/stable/
BLFS Book: https://www.linuxfromscratch.org/blfs/
LFS Mailing Lists: https://www.linuxfromscratch.org/mail.html
LFS Wiki: https://www.linuxfromscratch.org/lfs/wiki/
LFS FAQ: https://www.linuxfromscratch.org/faq/

Share Your Success!

Consider sharing your experience:

LFS mailing list
Online forums
Social media with #LinuxFromScratch
Blog about your journey

Enjoy your custom-built Linux system! 🎉🐧

Part 10 First Boot and Testing

Part 10: First Boot and Post-Installation

Overview

First Boot Procedure

1. Power On / Reboot

2. GRUB Boot Menu

3. Boot Messages

4. Login Prompt

Initial System Verification

1. Verify System is Running

2. Verify Filesystems

3. Test Network Connectivity

4. Test Package Management

5. Verify System Services

Post-Installation Configuration

1. Create Regular User Account

2. Configure Time and Date

3. Update System Clock from Internet

4. Configure SSH (if needed)

5. Set up Firewall (Optional)

System Testing

1. Reboot Test

2. Shutdown Test

3. Multi-User Test

4. Stress Test (Optional)

Troubleshooting Common Issues

Issue: No Network Connectivity

Issue: Cannot Login as Root

Issue: Services Won't Start

Issue: Kernel Panic on Boot

Beyond LFS: Next Steps

1. Install Additional Software (BLFS)

2. Create Automated Package Management

3. System Hardening

4. Backup Strategy

5. Document Your System

Performance Tuning

1. Optimize Boot Time

2. Filesystem Optimization

3. Kernel Optimization

Congratulations!

Final Checklist

Resources

Share Your Success!