PXE (Preboot eXecution Environment)

Environment

Package Installation

dnf install -y syslinux syslinux-tftpboot dnsmasq nfs-utils exportfs rsync

Package Configuration

• Mount Ubuntu Live Iso

  export ISO_MP='/media/iso'
  mkdir -p "$ISO_MP"
  mount /dev/sr0 "$ISO_MP"
  

• /etc/dnsmasq.conf

  # Listen on this specific port instead of the standard DNS port
  # (53). Setting this to zero completely disables DNS function,
  # leaving only DHCP and/or TFTP.
  port=0
  
  # If you want dnsmasq to listen for DHCP and DNS requests only on
  # specified interfaces (and the loopback) give the name of the
  # interface (eg eth0) here.
  # Repeat the line for more than one interface.
  interface=ens18
  
  # Uncomment this to enable the integrated DHCP server, you need
  # to supply the range of addresses available for lease and optionally
  # a lease time. If you have more than one network, you will need to
  # repeat this for each network on which you want to supply DHCP
  # service.
  dhcp-range=192.168.3.200,192.168.3.250,12h
  
  # Override the default route supplied by dnsmasq, which assumes the
  # router is the same machine as the one running dnsmasq.
  # Do the same thing, but using the option name
  dhcp-option=option:router,192.168.3.1
  dhcp-option=option:dns-server,192.168.3.1
  
  # Set the boot filename for netboot/PXE. You will only need
  # this if you want to boot machines over the network and you will need
  # a TFTP server; either dnsmasq's built-in TFTP server or an
  # external one. (See below for how to enable the TFTP server.)
  dhcp-boot=syslinux.efi
  
  # Enable dnsmasq's built-in TFTP server
  enable-tftp
  
  # Set the root directory for files available via FTP.
  tftp-root=/var/tftp
  
  # Log lots of extra information about DHCP transactions.
  log-dhcp
  

• Init TFTP server provided by dnsmasq

  TFTP only provides basic files for PXE, like bootloader, boot menu, and initrd entry.

  export TFTP_PATH='/var/tftp'
  mkdir -p "$TFTP_PATH"
  
  # PXE bootloader
  # Alter: copy these files from Ubuntu distro if files from rocky failed.
  cp /tftpboot/efi64/syslinux.efi "$TFTP_PATH"
  cp /tftpboot/efi64/ldlinux.e64 "$TFTP_PATH"
  
  # PXE boot menu
  mkdir "$TFTP_PATH/pxelinux.cfg"
  cat > "$TFTP_PATH/pxelinux.cfg/default" <<'EOF'
  DEFAULT ubuntu
  
  LABEL ubuntu
    KERNEL ubuntu/vmlinuz
    INITRD ubuntu/initrd
    APPEND boot=casper netboot=nfs nfsroot=192.168.3.11:/srv/ubuntu-live ip=dhcp ---
  
  EOF
  
  # PXE boot option1 - Ubuntu
  export TFTP_UBUNTU_PATH="$TFTP_PATH/ubuntu"
  mkdir -p "$TFTP_UBUNTU_PATH"
  cp "$ISO_MP/casper/initrd" "$TFTP_UBUNTU_PATH"
  cp "$ISO_MP/casper/vmlinuz" "$TFTP_UBUNTU_PATH"
  
  chown -R dnsmasq: "$TFTP_PATH"
  chcon -R -t tftpdir_t "$TFTP_PATH"
  

• Init NFS server

  NFS provides actual live OS because OS files is too large to TFTP for transfer. TFTP only transfer files with max size about 100M stably.

  export NFS_UBUNTU_PATH='/srv/ubuntu-live'
  mkdir -p "$NFS_UBUNTU_PATH"
  rsync -a "$ISO_MP/" "$NFS_UBUNTU_PATH/"
  chcon -R -t nfs_t "$NFS_UBUNTU_PATH"
  
  cat >> /etc/exports <<EOF
  $NFS_UBUNTU_PATH *(ro,sync,no_subtree_check)
  EOF
  

• Unmount Ubuntu Live Iso

  umount "$ISO_MP"
  rmdir "$ISO_MP"
  

Final Checks

• tree "$TFTP_PATH"

  /var/tftp
  ├── ldlinux.e64
  ├── pxelinux.cfg
  │   └── default
  ├── syslinux.efi
  └── ubuntu
      ├── initrd
      └── vmlinuz
  
  3 directories, 5 files
  

• tree -L 2 "$NFS_UBUNTU_PATH"

  /srv/ubuntu-live
  ├── boot
  │   ├── grub
  │   └── memtest86+x64.bin
  ├── boot.catalog
  ├── casper
  │   ├── filesystem.manifest
  │   ├── filesystem.size
  │   ├── initrd
  │   ├── install-sources.yaml
  │   ├── ubuntu-server-minimal.manifest
  │   ├── ubuntu-server-minimal.size
  │   ├── ubuntu-server-minimal.squashfs
  │   ├── ubuntu-server-minimal.squashfs.gpg
  │   ├── ubuntu-server-minimal.ubuntu-server.installer.generic.manifest
  │   ├── ubuntu-server-minimal.ubuntu-server.installer.generic.size
  │   ├── ubuntu-server-minimal.ubuntu-server.installer.generic.squashfs
  │   ├── ubuntu-server-minimal.ubuntu-server.installer.generic.squashfs.gpg
  │   ├── ubuntu-server-minimal.ubuntu-server.installer.manifest
  │   ├── ubuntu-server-minimal.ubuntu-server.installer.size
  │   ├── ubuntu-server-minimal.ubuntu-server.installer.squashfs
  │   ├── ubuntu-server-minimal.ubuntu-server.installer.squashfs.gpg
  │   ├── ubuntu-server-minimal.ubuntu-server.manifest
  │   ├── ubuntu-server-minimal.ubuntu-server.size
  │   ├── ubuntu-server-minimal.ubuntu-server.squashfs
  │   ├── ubuntu-server-minimal.ubuntu-server.squashfs.gpg
  │   └── vmlinuz
  ├── dists
  │   ├── noble
  │   ├── stable -> noble
  │   └── unstable -> noble
  ├── EFI
  │   └── boot
  ├── install
  ├── md5sum.txt
  ├── pool
  │   ├── main
  │   └── restricted
  └── ubuntu -> .
  
  15 directories, 24 files
  

Service Restart

firewall-cmd --permanent --add-service=dhcp
firewall-cmd --permanent --add-service=tftp

# NFS
firewall-cmd --permanent --add-service=nfs
firewall-cmd --permanent --add-service=rpc-bind
firewall-cmd --permanent --add-service=mountd

firewall-cmd --reload

systemctl enable --now dnsmasq
systemctl restart dnsmasq

exportfs -ra
systemctl enable --now nfs-server
systemctl restart nfs-server

Create another PXE client

• No disk or disc required for PXE boot
• Enable PXE boot

Troubleshoot

If your PXE client stucks at UEFI boot, your files in /var/tftp/ are possibly bad.

The Syslinux EFI implementation is incomplete/buggy in many RHEL/Fedora/Rocky builds, so you can copy them from Ubuntu repo directly.