xymondigest: 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/client/bin/xymondigest - from package: xymon-client
/usr/lib/xymon/server/bin/xymondigest - from package: xymon

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

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