hostgraphs.cgi: command not found

Have You tried accessing the binary with the full path?

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/hostgraphs.cgi - from package: xymon

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