convertnk: 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/lib/xymon/server/bin/convertnk - from package: xymon

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

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