(Server)
### /etc/dhcp/dhcpd.conf | grep -v '#' | sed '/^$/d' ###
option domain-name "nem264.cz";
option domain-name-servers 8.8.8.8;
default-lease-time 600;
max-lease-time 7200;
ddns-update-style none;
subnet 192.168.89.0 netmask 255.255.255.0 {
  range 192.168.89.100 192.168.89.200 ;
  option broadcast-address 192.168.89.255;
  option routers 192.168.89.2;
  next-server 192.168.89.2;
  filename "pxelinux.0";
}
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### cat /etc/default/isc-dhcp-server | grep -v '#' | sed '/^$/d' ###
INTERFACESv4="enp0s8"
INTERFACESv6=""
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### cat /etc/default/tftpd-hpa | grep -v '#' | sed '/^$/d' ###
TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/srv/tftp/nem264"
TFTP_ADDRESS="0.0.0.0:69"
TFTP_OPTIONS="--secure"
---------------------------------------------

### cat /etc/exports | grep -v '#' | sed '/^$/d' ###
/root_fs_nem264/     192.168.89.0/24(rw,async,no_root_squash)
/home/               192.168.89.0/24(rw,async)
---------------------------------------------

### cat /srv/tftp/nem264/pxelinux.cfg/default ###
# D-I config version 2.0
# search path for the c32 support libraries (libcom32, libutil etc.)

DEFAULT vesamenu.c32
PROMPT 0

MENU TITLE  Boot Menu

LABEL Debian - NetBoot
KERNEL /Debian/vmlinuz-4.19.0-14-amd64
APPEND initrd=/Debian/initrd.img-4.19.0-14-amd64 root=/dev/nfs nfsroot=192.168.89.2:/root_fs_nem264 ip=dhcp rw
---------------------------------------------

(Client)
### mount | grep nfs ###
192.168.89.2:/root_fs_nem264 on / type nfs (rw,relatime,vers=3,rsize=262144,wsize=262144,namlen=255,hard,nolock,proto=tcp,port=2049,timeo=7,retrans=10,sec=sys,local_lock=all,addr=192.168.89.2)
nfsd on /proc/fs/nfsd type nfsd (rw,relatime)
---------------------------------------------