xymond_hostdata: 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/xymond_hostdata - from package: xymon

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

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