PXE Server

PXE Server Setup for WFOS | Notion

To simplify the process, we have consolidated the content into pxe.sh. As a result, the new operational steps will be streamlined.

1. Installation

   sudo apt update
   sudo apt upgrade
   reboot
   sudo apt install vim tree isc-dhcp-server tftpd-hpa nfs-kernel-server apache2 syslinux pxelinux syslinux-efi -y

2. Adjust disk size

   sudo lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv
   sudo resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv

3. Set up DHCP server

   > sudo vim /etc/dhcp/dhcpd.conf
   
   # Add the following content
   subnet 10.217.35.0 netmask 255.255.255.0 {
     option routers 10.217.35.254;
     option broadcast-address 10.217.35.255;
     default-lease-time 600;
     max-lease-time 7200;
     next-server 10.217.35.1;
     # filename "pxelinux.0";
     filename "syslinux.efi";
   }
   > sudo vim /etc/default/isc-dhcp-server
   #  Add the following content
   INTERFACES="<INTERFACE_NAME>"

4. Set up TFTP server

   > sudo vim /etc/default/tftpd-hpa
   
   # Add the following content
   INTERFACESv4="<INTERFACE_NAME>"
   RUN_DAEMON="yes"

5. Prepare iso

   # install gdown
   sudo apt install pipx
   pipx ensurepath
   pipx install gdown
   
   # Using gdown download wfos.iso to /home/wfos.iso
   gdown 12ChOlTkt5KQ1-afXSd7PxhZbe27dedjV -O wfos.iso
   cp wfos.iso /home/wfos.iso

6. Set up NFS server

   > sudo vim /etc/exports
   
   # Add the following
   /var/nfs/ubuntu 10.217.35.0/24(ro,sync,no_root_squash,no_subtree_check)

7. Prepare pxe.sh and execute bash pxe.sh

   After this setup, the IP 10.217.35.1 will display the Apache server, which serves files located in /var/www/html. Therefore, to make any file accessible via HTTP, you simply need to place it in the /var/www/html/ directory.

   After execution, the /var/www/html/preseed directory will be overwritten by the command sudo cp -r /var/nfs/ubuntu/preseed /var/www/html. Therefore, make sure to update the contest.seed file to the latest version.

HTTP Server

In /http_server

• credentials.csv ：Prepare in advance: the MAC address, IP address, user, and password for each laptop.

  mac_address,ip,username,password
  e4:b9:7a:6d:48:a9,10.217.35.101,user01,f9Mppj6Gsn
  ...

• server.py ：http server。Execute the command python3 -m server & and then navigate to 10.217.35.235:8080/ip_address in a browser. If you see the expected output, the setup was successful.

• gen_config.py ：generate a DHCP configuration for specific IP addresses

  After executed python3 -m gen_config, you will get the following

  host client1 {
        hardware ethernet e4:b9:7a:6d:48:a9;
        fixed-address 10.217.35.101;
     }
  host client2 {
      hardware ethernet e4:b9:7a:71:7f:99;
      fixed-address 10.217.35.102;
  }
  host client3 {
      hardware ethernet e4:b9:7a:71:80:36;
      fixed-address 10.217.35.103;
  }
  ....
  

  Update dhcp config

  > sudo vim /etc/dhcp/dhcpd.conf
  
  subnet 10.217.35.0 netmask 255.255.255.0 {
    option routers 10.217.35.254;
    option broadcast-address 10.217.35.255;
    default-lease-time 600;
    max-lease-time 7200;
    next-server 10.217.35.1;
    # filename "pxelinux.0";
    filename "syslinux.efi";
    **host client1 {
        hardware ethernet e4:b9:7a:6d:48:a9;
        fixed-address 10.217.35.101;
     }
    host client2 {
        hardware ethernet e4:b9:7a:71:7f:99;
        fixed-address 10.217.35.102;
    }
    host client3 {
        hardware ethernet e4:b9:7a:71:80:36;
        fixed-address 10.217.35.103;
    }**
    ....
  }

After updating, it is necessary to restart the DHCP server (you can simply run the pxe.sh script again).

PXE Client by preseed

Prepare pre-file

1. /var/www/html/preseed/contest.seed/：The seed is a method used in Ubuntu 22.04 and earlier for unattended installations. It allows you to pre-define installation settings for Ubuntu by specifying them through commands in advance.

2. shell scripts

   • /var/www/html/init/init1.sh

   The script that needs to be executed after booting through SSH

   • /var/www/html/init/init2.sh

   • /var/www/html/init/init3.sh

Preseed file requirements confirmation

• Close Wifi、Bluetooth

  WFOS originally had these two functions disabled. To enable them, some operations require sudo privileges. Considering that participants won't have sudo access, it’s better to leave the settings as they are.

• NTP

  # In the original preseed file, change the following settings to "true".
  
  # from
  ~~d-i clock-setup/ntp boolean false~~
  
  # to
  d-i clock-setup/ntp boolean true
  d-i clock-setup/ntp-server string 10.217.35.254

• SSH login: Use SSH key pair for authentication.

  1. Add the public key used for SSH login to the ~/.ssh/authorized_keys file. First, generate a key pair on any computer that will be used for login

     # Enter this can generate the key pair
     ssh-keygen -t ed25519 -f nsspc -C "My WF 2024 Key" -N ''

  2. Open nsspc.pub, copy the content to the script

     mkdir -p /home/nsspc/.ssh
     
     # Write public key to /home/nsspc/.ssh/authorized_keys
     echo "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGCWcyLFGRahQp++AnBHZudCINgvspCYJvGGX0cUd1D9 My WF 2023 Key" > /home/nsspc/.ssh/authorized_keys

  3. Return to the computer used for login

     ssh -i ~/.ssh/nsspc nsspc@remote.host

  ---

• get username and password through http request，and add the new user

  username=$(wget -qO- http://10.217.35.235:8080/username)
  password=$(wget -qO- http://10.217.35.235:8080/password)
  sudo useradd -m -s /bin/bash $username
  echo "$username:$password" | sudo chpasswd

• Firewall

  Execute yes | sudo ufw enable。It cannot be successfully executed directly at boot, so you will see that the client's ufw status is inactivte

• node exporter、black box

  # In server, shloud download node_exporter-1.8.1.linux-amd64.tar.gz and blackbox_exporter-0.25.0.linux-amd64.tar.gz to var/www/html in advance，then client can get the files
  sudo wget https://github.com/prometheus/node_exporter/releases/download/v1.8.1/node_exporter-1.8.1.linux-amd64.tar.gz
  sudo wget https://github.com/prometheus/blackbox_exporter/releases/download/v0.25.0/blackbox_exporter-0.25.0.linux-amd64.tar.gz
  
  # client side
  cd /opt
  sudo wget -r -p -e robots=off -U mozilla http://10.217.35.1/node_exporter-1.8.1.linux-amd64.tar.gz
  cd 10.217.35.1/
  sudo tar xvfz node_exporter-1.8.1.linux-amd64.tar.gz
  cd node_exporter-1.8.1.linux-amd64/
  sudo ./node_exporter --collector.wifi &
  
  cd /opt
  sudo wget -r -p -e robots=off -U mozilla http://10.217.35.1/blackbox_exporter-0.25.0.linux-amd64.tar.gz
  cd 10.217.35.1/
  sudo tar xvfz blackbox_exporter-0.25.0.linux-amd64.tar.gz
  cd blackbox_exporter-0.25.0.linux-amd64/
  sudo ./blackbox_exporter &

  It also cannot be successfully executed directly at boot, so there are additional solutions for firewalls and node exporters.

  ufw, monitoring

  Execute init2.sh, init3.sh again after booting through ssh, and you will find that ufw and monitoring are successful. Execute python3 -m run_scripts directly on the server to complete all clients at once. (USB scripts can also be executed together)

  sudo apt install python3-paramiko
  python3 -m run_scripts