rackdiag: 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/bin/rackdiag - from package: python-nwdiag

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

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