showgraph.cgi: 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/showgraph.cgi - from package: xymon

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

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