Procedure

1. Install the dracut-network package:

   # yum install dracut-network

2. After installing the dracut-network package, add the following line to /etc/dracut.conf:

   add_dracutmodules+="nfs"

To Configure tftp

1. Enable PXE booting over the network:

   # systemctl enable --now tftp

2. The tftp root directory (chroot) is located in /var/lib/tftpboot. Copy /usr/share/syslinux/pxelinux.0 to /var/lib/tftpboot/:

   # cp /usr/share/syslinux/pxelinux.0 /var/lib/tftpboot/

3. Create a pxelinux.cfg directory inside the tftp root directory:

   # mkdir -p /var/lib/tftpboot/pxelinux.cfg/

4. After configuring tftp for diskless clients, configure DHCP, NFS, and the exported file system accordingly.

Procedure

1. Set up a DHCP server and enable PXE booting by adding the following configuration to /etc/dhcp/dhcpd.conf:

   allow booting;
   allow bootp;
   subnet 192.168.205.0 netmask 255.255.255.0 {
     pool
     {
       range 192.168.205.10 192.168.205.25;
     }
   
     option subnet-mask 255.255.255.0;
     option routers 192.168.205.1;
   }
   class "pxeclients" {
      match if substring(option vendor-class-identifier, 0, 9) = "PXEClient";
      next-server server-ip;
      filename "pxelinux.0";
   }

   This configuration will not boot over UEFI. To perform installation for UEFI, follow the procedure from this documentation: Configuring a TFTP server for UEFI-based clients. Also, note that the /etc/dhcp/dhcpd.conf is an example file.

   Note

   When libvirt virtual machines are used as a diskless client, libvirt provides the DHCP service and the stand alone DHCP server is not used. In this situation, network booting must be enabled with the bootp file='filename' option in the libvirt network configuration, virsh net-edit.

2. Enable dhcpd.service by entering the following command:

   # systemctl enable --now dhcpd.service

Procedure

1. Configure the NFS server to export the root directory by adding it to /etc/exports. For the instructions see NFS server configuration.

2. To accommodate completely diskless clients, the root directory should contain a complete Red Hat Enterprise Linux installation. You can either install a new base system or clone an existing installation:

   • To install Red Hat Enterprise Linux to the exported location, use the yum utility with the --installroot option:

     # yum install @Base kernel dracut-network nfs-utils \
           --installroot=exported-root-directory --releasever=/

   • To synchronize with a running system, use the rsync utility:

     # rsync -a -e ssh --exclude='/proc/' --exclude='/sys/' \
            example.com:/exported-root-directory

     • Replace hostname.com with the hostname of the running system with which to synchronize via rsync.

     • Replace exported-root-directory with the path to the exported file system.

       Note, that for this option you must have a separate existing running system, which you will clone to the server by the command above.

Configure File System

1. Select the kernel that diskless clients should use (vmlinuz-kernel-version) and copy it to the tftp boot directory:

   # cp /exported-root-directory/boot/vmlinuz-kernel-version /var/lib/tftpboot/

2. Create the initrd (that is, initramfs-kernel-version.img) with NFS support:

   # dracut --add nfs initramfs-kernel-version.img kernel-version

3. Change file permissions for initrd to 644 using the following command:

   # chmod 644 /exported-root-directory/boot/initramfs-<kernel-version>.img

   Warning

   If you do not change the initrd’s file permissions, the pxelinux.0 boot loader will fail with a "file not found" error.

4. Copy the resulting initramfs-kernel-version.img into the tftp boot directory:

   # cp /exported-root-directory/boot/initramfs-kernel-version.img /var/lib/tftpboot/

5. Edit the default boot configuration to use the initrd and kernel in the /var/lib/tftpboot/ directory. This configuration should instruct the diskless client’s root to mount the exported file system (/exported-root-directory) as read-write. Add the following configuration in the /var/lib/tftpboot/pxelinux.cfg/default file:

   default rhel8
   
   label rhel8
     kernel vmlinuz-kernel-version
     append initrd=initramfs-kernel-version.img root=nfs:server-ip:/exported-root-directory rw

   Replace server-ip with the IP address of the host machine on which the tftp and DHCP services reside.

6. Reboot the NFS server.

Procedure

1. To change the user password, follow the steps below:

   • Change the command line to /exported/root/directory:

     # chroot /exported/root/directory /bin/bash

   • Change the password for the user you want:

     # passwd <username>

     Replace the <username> with a real user to whom you want to change the password.

   • Exit the command line:

     # exit

2. To install software to a remote diskless system, use the following command:

   # yum install <package> --installroot=/exported/root/directory --releasever=/ --config /etc/dnf/dnf.conf --setopt=reposdir=/etc/yum.repos.d/

   Replace <package> with the actual package you want to install.

3. To split a remote diskless system into a /usr and a /var you must configure two separate exports. Read NFS server configuration documentation for details.