corosync-blackbox: 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/bin/corosync-blackbox - from package: corosync

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

On Debian possible default full paths are:

/usr/bin/corosync-blackbox - from package: corosync

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

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