sitesummary-update-munin: 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/sbin/sitesummary-update-munin - from package: sitesummary

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

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