xymond_client: 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_client - from package: xymon

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

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