@boros There is no RHEL/CentOS since they are both dead to me now that IBM had its way…
BUT, someone with the proper motivation can probably make it work. I would start with my post here: https://forums.fogproject.org/post/103324 That will give you the basic layout. Now lets mix it with these instructions. https://docs.centos.org/en-US/8-docs/advanced-install/assembly_preparing-for-a-network-install/
The most useful section is from the syslinux boot menu.
label linux
menu label ^Install system
menu default
kernel images/CentOS-8/vmlinuz
append initrd=images/CentOS-8/initrd.img ip=dhcp inst.repo=http://10.32.5.1/CentOS-8/x86_64/iso-contents-root/
While FOG uses iPXE its possible to translate between the two formats. From the first link this is what I used to call centos 7 installer.
kernel tftp://${fog-ip}/os/centos/7/vmlinuz
initrd tftp://${fog-ip}/os/centos/7/initrd.img
imgargs vmlinuz initrd=initrd.img root=live:nfs://${fog-ip}:/images/os/centos/7/LiveOS/squashfs.img ip=dhcp inst.repo=nfs:${fog-ip}:/images/os/centos/7 splash quiet
boot || goto MENU
So to update the syslinux format to iPXE
kernel tftp://${fog-ip}/os/centos/8/vmlinuz
initrd tftp://${fog-ip}/os/centos/8/initrd.img
imgargs vmlinuz initrd=initrd.img ip=dhcp inst.repo=http://${fog-ip}/centos8/ splash quiet
boot || goto MENU
So you will need to copy vmlinuz and initrd.img from the iso to the fog server into /tftpboot/os/centos/8 directory. This places the boot files in scope of the tftp server. The next is to place the contents of the iso (extracted) into the scope of the web server in /var/www/html/centos8 directory. So the target computer will load linux and the initrd from the tftp server and then access the rest of the centos files from the contents uploaded to the web server.