safe_asterisk: 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/safe_asterisk - from package: asterisk

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

On Debian possible default full paths are:

/usr/sbin/safe_asterisk - from package: asterisk

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

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