rpc.nfsd: command not found

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 CentOS possible default full paths are:

/usr/sbin/rpc.nfsd - from package: nfs-utils

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/rpc.nfsd - from package: nfs-kernel-server

You may install the required package with command apt-get install {package}

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