PXE server can't mount NFS

on a test machine, I tried to install PXE to make it easier for the server to install OS systems

my settings simple

# /etc/default/tftpd-hpaTFTP_USERNAME="tftp"TFTP_DIRECTORY="/var/lib/tftpboot"TFTP_ADDRESS="0.0.0.0:69"TFTP_OPTIONS="--secure"

for example records/var/lib/tftpboot/pxelinux.cfg/linux

label ubuntu64  menu label Ubuntu 18.04 amd64 Netinstall  kernel images/linux/ubuntu18/amd64/linux  initrd images/linux/ubuntu18/amd64/initrd.gz

work fine, all good but if i try run this

label SystemRescueCD  kernel images/utils/SystemRescueCD/isolinux/rescue64  append initrd=images/utils/SystemRescueCD/isolinux/initram.igz dodhcp nfsboot=192.196.0.5:/var/lib/tftpboot/images/utils/SystemRescueCD

or

label Kaspersky Rescue Disk v 10    menu label Kaspersky Rescue Disk v10    linux kav/boot/rescue    append initrd=kav/boot/rescue.igz root=/dev/nfs netboot=nfs nfsroot=192.196.0.5:/var/lib/tftpboot/kav initrd=kav/boot/rescue.igz

i have error when booting:

mount: 192.196.0.5:/var/lib/tftpboot/images/utils/SystemRescueCD failed, reason given by server: Permission deniedmount: mounting 192.196.0.5:/var/lib/tftpboot/images/utils/SystemRescueCD on /boot failed: Bad file descriptorCannot mount NFS: mount -t nfs -o intr,nolock,rsize=1024.... cannot complete the boot process

on tftp folder I have possible rights 755 Permissions

chown -R root:nogroup /var/lib/tftpboot

I understand that this is related to NFS, but I don’t know where to look?