TFTP stands for Trivial File Transfer Protocol. Unlike FTP, which relies on TCP for connection-oriented transfers, TFTP uses UDP (User Datagram Protocol) to transfer data quickly and with minimal overhead.
TFTP is commonly used for serving boot files to diskless workstations (thin clients) or starting automated network installations of operating systems.
In this article, we will set up a TFTP server with minimal configurations. We will use the same CentOS 7 machine we configured as a DHCP server in the previous guide, leveraging the pre-installed utilities and settings.
1. Installing TFTP & Bootloader Packages
Install the TFTP server along with the syslinux-tftpboot package. The syslinux package provides the necessary PXE bootloaders (like pxelinux.0) which will be served to clients attempting to boot from the network:
yum install tftp-server syslinux-tftpboot -y2. Basic System Preparation
Enable TFTP on Startup
Ensure the TFTP service starts automatically during system boot:
systemctl enable tftp.serviceOpen Firewall Ports
Allow incoming TFTP traffic in the local firewall (TFTP relies on UDP port 69):
firewall-cmd --permanent --zone=public --add-service=tftpReload Firewall
Force the firewalld daemon to reload and apply the newly added services:
firewall-cmd --reloadVerify Firewall Open Services
Confirm that the tftp service is listed in active firewalld rules:
firewall-cmd --list-all3. Configuring the TFTP Server
The TFTP server on CentOS 7 is managed via xinetd. Follow these steps to configure it securely.
Backup Default Configuration
cp /etc/xinetd.d/tftp /root/tftp.bakReset Configuration File
>/etc/xinetd.d/tftpSetup Custom TFTP Settings
Paste the following configuration block to set up the xinetd service configuration for TFTP, pointing to /var/lib/tftpboot as the root directory for system files:
cat > /etc/xinetd.d/tftp <<EOF
# default: off
# description: The tftp server serves files using the trivial file transfer
# protocol. The tftp protocol is often used to boot diskless
# workstations, download configuration files to network-aware printers,
# and to start the installation process for some operating systems.
service tftp
{
socket_type = dgram
protocol = udp
wait = yes
user = root
server = /usr/sbin/in.tftpd
server_args = -s -v -v -v /var/lib/tftpboot
disable = no
per_source = 11
cps = 100 2
flags = IPv4
}
EOF4. Starting the Service
Start the TFTP server and confirm that it is active and running under xinetd:
systemctl start tftp.service && systemctl status tftp.serviceTroubleshooting Logs
If you encounter any errors starting the service or binding to the UDP interface, audit the system messages log:
tail /var/log/messages5. Integrating TFTP with your DHCP Server
Your TFTP server is now ready to serve network bootloader files to thin clients!
To allow PXE booting clients to discover your TFTP server, you must update your DHCP server configuration with the filename and server IP.
Below is the specific snippet of the DHCP subnet block we configured in the DHCP Guide, pointing to the pxelinux.0 bootloader and setting the TFTP host IP (next-server):
subnet 172.16.99.0 netmask 255.255.255.0 {
option broadcast-address 172.16.99.255;
option routers 172.16.99.1;
# Point PXE clients to the network bootloader file
filename "/pxelinux.0";
pool {
range 172.16.99.150 172.16.99.230;
}
group {
# IP or hostname of your TFTP Server
next-server lhr-pxe1.induslevel.com;
host tclient110 {
hardware ethernet 00:0c:29:d3:a1:d1;
fixed-address 172.16.99.110;
option host-name "tclient110.induslevel.local";
}
}
}What's Next?
In the next article in this PXE server series, we will set up and configure a Local Yum Repository. This repository will host the packages required to install a hardened, security-compliant version of CentOS 7 directly over the network, automating system setups completely!
