Preboot eXecution Environment

Lab 01: PXE Ubuntu Netboot

Server:

Client:

1. Server

Install dnsmasq

$ apt install dnsmasq

Setup interface.

$ ip link add br0 type bridge
$ ip addr add 192.168.0.1/24 dev br0
$ ip link set br0 up

Edit /etc/dnsmasq.conf

interface=br0
dhcp-range=192.168.0.50,192.168.0.150,12h
dhcp-boot=pxelinux.0
enable-tftp
tftp-root=/var/ftpd

Start server.

$ systemctl start dnsmasq

Setup boot directory.

$ mkdir /var/ftpd
$ cd /var/ftpd

$ wget http://archive.ubuntu.com/ubuntu/dists/bionic-updates/main/installer-amd64/current/images/netboot/netboot.tar.gz
$ tar xf netboot.tar.gz

Workaround: Enable serial console.

Prepend to /var/ftpd/pxelinux.cfg/default

console 0
serial 0 19200 0

Edit /var/ftpd/ubuntu-installer/amd64/boot-screens/txt.cfg.

label install
    menu label ^Install
    menu default
    kernel ubuntu-installer/amd64/linux
    # append vga=788 initrd=ubuntu-installer/amd64/initrd.gz --- quiet
    append initrd=ubuntu-installer/amd64/initrd.gz --- console=ttyS0,19200 earlyprint=serial,ttyS0,19200

2. Client

$ virt-install --name=vm1 \
    --ram=2048 \
    --disk size=16 \
    --pxe --boot network,menu=on \
    --network bridge=br0 \
    --os-variant ubuntu18.04 \
    --nographic


Lab 02: NFS Root Filesystem

Continue of lab 01.

Server:

Client

1. Server

Copy linux kernel and initrd to ftpd directory.

$ cp vmlinuz-5.15.0-164-generic /var/ftpd
$ cp initrd.img-5.15.0-164-generic /var/ftpd

Edit /var/ftpd/ubuntu-installer/amd64/boot-screens/txt.cfg

label install
    menu label ^Install
    menu default
    kernel vmlinuz-5.15.0-164-generic
    append initrd=initrd.img-5.15.0-164-generic root=/dev/nfs nfsroot=192.168.0.1:/var/nfs --- console=ttyS0,19200 earlyprint=serial,ttyS0,19200

Prepare root filesystem.

Setup NFS server.

Edit /etc/exports.

/var/nfs *(rw, sync, no_subtree_check, no_root_squash)

Export nfs directory.

$ export -a
$ export -v

2. Client

$ virt-install --name=vm1 \
    --ram=2048 \
    --disk size=16 \
    --pxe --boot network,menu=on \
    --network bridge=br0 \
    --os-variant ubuntu18.04 \
    --nographic


Boot Process

Server Log.

$ journalctl -f -u dnsmasq
Jan 23 08:02:42 pc dnsmasq-dhcp[5179]: DHCPDISCOVER(br0) 52:54:00:63:77:ac
Jan 23 08:02:42 pc dnsmasq-dhcp[5179]: DHCPOFFER(br0) 192.168.0.50 52:54:00:63:77:ac
Jan 23 08:02:45 pc dnsmasq-dhcp[5179]: DHCPREQUEST(br0) 192.168.0.50 52:54:00:63:77:ac
Jan 23 08:02:45 pc dnsmasq-dhcp[5179]: DHCPACK(br0) 192.168.0.50 52:54:00:63:77:ac

Jan 23 08:02:46 pc dnsmasq-tftp[5179]: sent /var/ftpd/pxelinux.0 to 192.168.0.50
Jan 23 08:02:46 pc dnsmasq-tftp[5179]: sent /var/ftpd/ldlinux.c32 to 192.168.0.50

Jan 23 08:02:46 pc dnsmasq-tftp[5179]: sent /var/ftpd/pxelinux.cfg/default to 192.168.0.50
Jan 23 08:02:47 pc dnsmasq-tftp[5179]: sent /var/ftpd/ubuntu-installer/amd64/boot-screens/stdmenu.cfg to 192.168.0.50
Jan 23 08:02:47 pc dnsmasq-tftp[5179]: sent /var/ftpd/ubuntu-installer/amd64/boot-screens/txt.cfg to 192.168.0.50
Jan 23 08:02:47 pc dnsmasq-tftp[5179]: sent /var/ftpd/ubuntu-installer/amd64/boot-screens/stdmenu.cfg to 192.168.0.50
Jan 23 08:02:47 pc dnsmasq-tftp[5179]: sent /var/ftpd/ubuntu-installer/amd64/boot-screens/adtxt.cfg to 192.168.0.50
Jan 23 08:02:47 pc dnsmasq-tftp[5179]: sent /var/ftpd/ubuntu-installer/amd64/boot-screens/rqtxt.cfg to 192.168.0.50

Jan 23 08:03:00 pc dnsmasq-tftp[5179]: sent /var/ftpd/vmlinuz-5.15.0-164-generic to 192.168.0.50
Jan 23 08:04:59 pc dnsmasq-tftp[5179]: sent /var/ftpd/initrd.img-5.15.0-164-generic to 192.168.0.50
File Usage
pxelinux.0 PXE bootloader. Loads config, kernel, initrd.
pxelinux.cfg/default Configuration and boot menu.
vmlinuz Linux kernel.
initrd.img Initial RAM disk. Temporary rootfs in RAM to load drivers and mount real rootfs. 
sequenceDiagram
    Client ->> Server: DHCPDISCOVER
    Server ->> Client: DHCPOFFER    
    Client ->> Server: DHCPREQUEST
    Server ->> Client: DHCPACK
    Server ->> Client: pxelinux.0
    Server ->> Client: pxelinux.cfg/default
    Server ->> Client: vmlinuz
    Server ->> Client: initrd.img


References