rhnsd: 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/rhnsd - from package: rhnsd

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

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