nullidentd: 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 Debian possible default full paths are:

/usr/sbin/nullidentd - from package: nullidentd

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

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