fai-nfsroot2image: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/sbin/fai-nfsroot2image - from package: fai-server

You may install the required package with command apt-get install {package}
Error in other languages:
fai-nfsroot2image: bevel nie gevind nie
fai-nfsroot2image: comandă negăsită
fai-nfsroot2image: comando não encontrado
fai-nfsroot2image: commande introuvable
fai-nfsroot2image: command not found
fai-nfsroot2image: käsku ei ole
fai-nfsroot2image: không tìm thấy lệnh
fai-nfsroot2image: komanda nerasta
fai-nfsroot2image: Kommando nicht gefunden.
fai-nfsroot2image: kommandot finns inte
fai-nfsroot2image: komut yok
fai-nfsroot2image: nie znaleziono polecenia
fai-nfsroot2image: níor aimsíodh an t-ordú
fai-nfsroot2image: no se encontró la orden
fai-nfsroot2image: no s'ha trobat l'ordre
fai-nfsroot2image: opdracht niet gevonden
fai-nfsroot2image: parancs nem található
fai-nfsroot2image: perintah tidak ditemukan
fai-nfsroot2image: príkaz nenájdený
fai-nfsroot2image: příkaz nenalezen
fai-nfsroot2image: команда не найдена
fai-nfsroot2image: командата не е открита
fai-nfsroot2image: 命令找不到
fai-nfsroot2image: コマンドが見つかりません