munin-sched: 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 CentOS possible default full paths are:

/usr/sbin/munin-sched - from package: munin

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/munin-sched - from package: munin-node

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

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