killall5: 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:

/sbin/killall5 - from package: sysvinit-tools

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

On Debian possible default full paths are:

/sbin/killall5 - from package: sysvinit-utils

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

Error in other languages:
killall5: bevel nie gevind nie
killall5: comandă negăsită
killall5: comando não encontrado
killall5: commande introuvable
killall5: command not found
killall5: käsku ei ole
killall5: không tìm thấy lệnh
killall5: komanda nerasta
killall5: Kommando nicht gefunden.
killall5: kommandot finns inte
killall5: komut yok
killall5: nie znaleziono polecenia
killall5: níor aimsíodh an t-ordú
killall5: no se encontró la orden
killall5: no s'ha trobat l'ordre
killall5: opdracht niet gevonden
killall5: parancs nem található
killall5: perintah tidak ditemukan
killall5: príkaz nenájdený
killall5: příkaz nenalezen
killall5: команда не найдена
killall5: командата не е открита
killall5: 命令找不到
killall5: コマンドが見つかりません